INTRODUCTION — Diet is one of the most important behavioral aspects of diabetes treatment. Basic principles of nutritional management, however, are often poorly understood by both clinicians and their patients. The role of nutrition and the development of a medical nutrition therapy (MNT) plan for a patient with type 2 diabetes are discussed here. Nutrition for patients with type 1 diabetes, as well as diets for the prevention of diabetes and for weight loss in general, are discussed separately.
●(See "Nutritional considerations in type 1 diabetes mellitus".)
●(See "Prevention of type 2 diabetes mellitus", section on 'Diet'.)
●(See "Obesity in adults: Dietary therapy".)
MEDICAL NUTRITION THERAPY
Definition — Medical nutrition therapy (MNT) is the process by which a registered dietitian-nutritionist (RDN) tailors a meal planning approach for people with diabetes based on medical, lifestyle, and personal factors, and it is an integral component of diabetes management and diabetes self-management education [1]. Randomized controlled trials of MNT compared with usual care (initial lifestyle consult with infrequent follow-up) have demonstrated decreases in glycated hemoglobin (A1C) of approximately 2 percent in newly diagnosed type 2 diabetes patients and 1 percent in patients with an average four years' duration of type 2 diabetes [2-5].
The five components of MNT include:
●Weight management and increased physical activity
●Caloric intake (balanced with caloric expenditure)
●Consistency in day-to-day carbohydrate intake at meals and snacks
●Nutritional content
●Timing of meals and snacks
Meal content, quantity, and timing are particularly important for patients who are treated with insulin secretagogues or traditional insulin regimens.
The process of MNT involves selecting an appropriate meal planning approach and educational materials based on assessment of a person's ability or willingness to learn, motivation to make changes in eating habits, clinical and nutrition goals, diabetes medications, activity level, and lifestyle [6,7]. MNT clinical practice guidelines recommend a series of three to six encounters with a registered dietitian lasting for 45 to 90 minutes. The series of encounters should ideally begin at diagnosis of diabetes or at first referral to a dietitian for MNT and should be completed within six months. The dietitian can then reassess diabetes-related outcomes and discuss with the patient whether additional MNT encounters are needed. At least one follow-up MNT encounter is recommended annually to reinforce lifestyle changes and evaluate and monitor diabetes-related outcomes [1].
Goals — The medical nutrition therapy (MNT) plan for patients with type 2 diabetes should optimally manage the "ABCs" of diabetes control: glycated hemoglobin (A1C), blood pressure, and low-density lipoprotein (LDL) cholesterol. The MNT plan must be tailored for the individual patient to further address existing or at-risk complications related to diabetes or other concomitant conditions.
The nutritional goals for people with type 2 diabetes are to:
●Maintain blood glucose levels as near-normal as possible by balancing food intake with activity and medications or insulin
●Achieve optimal blood pressure and lipid levels
●Provide appropriate calories for achieving and maintaining a healthy, desirable body weight
●Manage risk factors and prevent complications of diabetes, both acute (hypoglycemia and short-term illness) and long term (gastroparesis, cardiovascular disease [CVD], renal disease, and other consequences of micro- and macrovascular disease)
●Address individual nutrition needs, incorporating personal and cultural preferences, willingness to change, and maintenance of the pleasure of eating by restricting choice only when clearly appropriate
The relative importance of each nutritional goal varies with individual patient characteristics.
Weight and caloric assessment
Estimating body mass index — Body mass index (BMI) is now commonly used in research and clinical care as a classification of weight status and is calculated as: weight in kg divided by (height in m)2 (calculator 1). Optimal body weight is usually a BMI between 18.5 and 24.9 kg/m2. BMI targets may vary depending on ethnicity (eg, lower for Asian populations) and muscularity (eg, higher for very muscular persons). (See "Obesity in adults: Prevalence, screening, and evaluation", section on 'Body mass index'.)
Healthy body weight range can also be roughly estimated by adding and subtracting 10 percent to the weights calculated as follows [8]:
●For women over 5 feet (152 cm):
•100 lb (45 kg) plus 5 lb (2.3 kg) for each additional inch (2.5 cm)
●For women under 5 feet (152 cm):
•100 lb (45 kg) minus 5 lb (2.3 kg) for each additional inch (2.5 cm) under 5 feet
●For men over 5 feet (152 cm):
•106 lb (48 kg) plus 6 lb (2.7 kg) for each additional inch (2.5 cm)
Estimating caloric intake — The importance of caloric intake for an individual patient is dependent on several factors, including the following:
●Current weight in relationship to healthy body weight
●Weight history
●Fat distribution and waist circumference
●Muscle mass
●Genetics
●A1C
Several formulas are available to estimate baseline caloric intake for weight maintenance. A commonly used formula considers the patient's age, sex, height, weight, and usual level of physical activity (table 1) [9].
A rough estimate of daily caloric needs to maintain body weight can be determined as follows [10]:
●Men and active women – 15 kcal/lb
●Most women, sedentary men, and adults over 55 years – 13 kcal/lb
●Sedentary women and adults with obesity – 10 kcal/lb
●Pregnant, lactating women – 15 to 17 kcal/lb
If patients have been close to healthy weight for several years, their current caloric intake is most likely appropriate.
To estimate caloric needs for weight loss of 1 to 2 pounds per week, subtract 500 to 1000 calories from daily weight maintenance calories.
Weight management — Major emphasis should be placed on portion control and healthy food choices to lower caloric intake and induce weight loss for patients with type 2 diabetes who are overweight (BMI ≥25 to 29.9 kg/m2) and obese (BMI ≥30 kg/m2), as weight loss can improve all three ABCs of diabetes control simultaneously. Improved glycemic control induced by weight loss is associated with partial correction of the two major metabolic abnormalities in type 2 diabetes: insulin resistance and impaired insulin secretion [11].
Caloric restriction, even before significant weight loss, will result in short-term improvement in glycemic control. Fasting blood glucose (FBG) falls within several days of calorie restriction, possibly due to a fall in hepatic glucose output [2,11,12]. However, long-term reduction in FBG concentration depends upon weight loss; blood glucose values increase slightly when the patient resumes a weight maintenance diet [2].
Weight loss goals — For patients with type 2 diabetes who are overweight (BMI ≥25 to 29.9 kg/m2) or obese (BMI ≥30 kg/m2), initial recommendations for weight loss and physical activity are to lose 5 to 10 percent of initial body weight [13] and to accumulate at least 30 minutes of moderate physical activity over the course of most days of the week [14,15]. Once initial weight goals are met, further goals should be determined based on assessment of the impact of the weight loss on FBG and the patient's willingness to lose more weight.
Patients need not reach ideal body weight to achieve improvement in health status, particularly if the patient engages in regular exercise [16]. A sustained weight loss of even 5 to 10 percent of initial body weight in overweight individuals can have a lasting beneficial impact on serum glucose, dyslipidemia, and hypertension [13,14,17-19]. In Look AHEAD (Action for Health in Diabetes), a randomized trial of an intensive lifestyle intervention to increase physical activity and decrease caloric intake versus standard diabetes education in people with type 2 diabetes, a modest weight loss of 8.6 percent of initial weight at one year was associated with significant improvements in blood pressure, glycemic control, FBG, high-density lipoprotein (HDL) cholesterol, and triglyceride levels and significant reductions in the use of diabetes, hypertension, and lipid-lowering medications [20]. After a median follow-up of 9.6 years, the difference in weight loss was attenuated but remained significant, and there were greater reductions in A1C and improvements in fitness and some cardiovascular risk factors [21]. The cardiovascular effects of the intensive lifestyle intervention are reviewed in detail separately. (See "Initial management of hyperglycemia in adults with type 2 diabetes mellitus", section on 'Intensive lifestyle modification'.)
The Look AHEAD trial and the Diabetes Remission Clinical Trial (DiRECT) both highlight the potential role of weight loss in achieving diabetes remission. In Look AHEAD, patients in the lifestyle intervention were more likely to experience complete or partial remission of diabetes compared with the diabetes support and education group (11.5 percent during the first year and 7.3 percent at year 4, compared with 2 percent for the diabetes support and education group at both time points) [22]. In the DiRECT trial, which included patients with type 2 diabetes with shorter duration diabetes than in Look AHEAD and not treated with insulin at baseline, weight loss associated with the lifestyle intervention resulted in diabetes remission at one year in 46 percent of patients, compared with 4 percent in the control group [23]. Remission rates were associated with the magnitude of weight loss, increasing from 7 to 86 percent as weight loss increased from <5 to >15 percent.
Weight loss strategies — Physical activity, diet, and behavioral modification are important components of all programs to accomplish weight loss. There are additional options for weight loss, including the addition of medication to promote weight loss and bariatric surgery. (See "Obesity in adults: Overview of management".)
Diet modification — Several meal planning strategies may accomplish a low-calorie diet. These include counting calories and grams of fat, use of meal replacements, and a detailed exchange system for meal planning. The relative effectiveness of each of these options has not been adequately studied.
Considerable controversy exists concerning low-carbohydrate versus low-fat, low-calorie diets. (See 'Nutritional content' below and "Obesity in adults: Dietary therapy", section on 'Choosing a diet'.)
●Counting calories and fat grams – Counting calories and fat is a well-recognized means of weight loss and was the strategy selected for achieving weight reduction for both the Diabetes Prevention Program (DPP) and Look AHEAD trials [24,25]. Participants were coached on calorie and fat gram counting and given reference booklets. Calorie and fat gram targets were based on initial body weight and targets were selected to promote weight loss of 1 to 2 pounds per week, providing 25 to 30 percent of calories from fat and <10 percent saturated fat. In Look AHEAD, the calorie and fat gram goals were as follows:
•Persons weighing less than 114 kg (250 lb):
-1200 to 1500 kcal per day, 40 to 50 g fat per day
•Persons weighing 114 kg (250 lb) or more:
-1500 to 1800 kcal per day, 50 to 60 g fat per day
It is important that low-calorie diets (less than 1200 kcal/day) are not adopted without review to be sure nutritional needs are met. Very low calorie diets (less than 800 kcal/day) require medical supervision. (See "Obesity in adults: Dietary therapy", section on 'Very low calorie diets'.)
●Meal replacements – Meal replacements can facilitate weight loss, improve glycemia, reduce cardiovascular risk factors, and promote effective weight maintenance for periods as long as four to five years [23,26-32]. Formula shakes, bars, or soups can be used to replace some (or all) meals and snacks to achieve weight loss and weight maintenance. As examples:
•Use of prepackaged meal replacements, compared with calorie-equivalent usual care diet, in 119 patients with type 2 diabetes resulted in greater weight loss (-3.0±5.4 kg versus -1.0±3.8 kg), improved glycemic control with lower A1C levels, improved quality of life, and better adherence with diet recommendations after one year [26].
•The use of liquid meal replacements for 12 weeks in people with type 2 diabetes resulted in significantly greater weight losses and reductions in fasting blood glucose than a conventional reducing diet with the same calorie goal [33].
Meal replacements in the form of liquid shakes and bars and portion-controlled servings of conventional foods have been used in both the DPP and Look AHEAD. In the Look AHEAD lifestyle intervention, use of meal replacements, which was not a randomized intervention, was associated with significantly more weight loss. Although this association should not be used to suggest causality, it is notable that the lifestyle intervention participants with the highest meal replacement use (approximately 12 meal replacements per week) had a mean weight loss of 11.2 percent, and those with the lowest use (approximately two meal replacements per week) lost 5.9 percent of initial weight after the first year of the intervention [34].
●Exchange system approach – The exchange system was developed in 1950 by the American Dietetic Association (now called the Academy of Nutrition and Dietetics), the American Diabetes Association (ADA), and the United States Public Health Service as an educational tool to provide consistency in meal planning and allow a wider variety of food choices for people with diabetes [35]. Originally, the exchange lists categorized foods into six groups: starch/bread, meat and meat substitutes, vegetables, fruit, milk, and fat. Each portion of food listed within a group was "exchangeable" because it contained approximately the same nutritional value in terms of calories, carbohydrate, protein, and fat.
The food groups have been more recently categorized into three groups, to simplify the teaching of carbohydrate consistency concepts. These three groups are carbohydrate, meat and meat substitutes, and fat (table 2 and table 3). The exchange lists also identify foods that are good sources of fiber and foods that have a high sodium content.
The exchange system meal planning approach can be used as a tool to help patients achieve calorie, fat, and carbohydrate goals (see 'Carbohydrate consistency' below). However, many patients find that it is a complicated system to learn.
Medications and surgery for weight loss — Medication to promote weight loss may be a reasonable intervention in patients who are having difficulty losing weight. The long-term benefits and risks of this approach are unknown. Surgery may also be appropriate for some patients with diabetes whose BMI is ≥35 kg/m2 and can result in significant improvement in glycemic control and other obesity-related morbidity and mortality [1]. These topics are reviewed in detail elsewhere. (See "Obesity in adults: Drug therapy" and "Bariatric surgery for management of obesity: Indications and preoperative preparation".)
Increased physical activity/exercise — Exercise is an important component of diabetes management. Benefits of exercise include improved glycemic control, weight control, reduction in comorbidities (hypertension, dyslipidemia, cardiovascular disease [CVD], and depression), and improved quality of life. (See "Exercise guidance in adults with diabetes mellitus", section on 'Exercise guidance'.)
Patients with diabetes, in particular those treated with medications that can cause hypoglycemia (such as insulin or sulfonylureas), should check blood glucose levels before and after exercising, especially in the beginning of an exercise program as patterns are established. Monitoring of blood glucose can both identify hypoglycemia and provide feedback to patients on the beneficial impact of exercise on glycemic control. (See 'Hypoglycemia' below.)
Nutritional counseling for all patients with type 2 diabetes — Nutritional issues for consideration in all patients with type 2 diabetes include consistency with carbohydrate intake and meal timing, macronutrient content of meals, avoidance of hypoglycemia, and dietary compliance.
Consistency with carbohydrate intake and meal timing day to day, to avoid erratic blood glucose levels and hypoglycemia, is most important when patients with type 2 diabetes are treated with some insulin regimens, sulfonylureas, or other secretagogues [1].
Carbohydrate consistency — Although patients with type 2 diabetes are more resistant to hypoglycemia than patients with type 1 diabetes, patients who are treated with hypoglycemic medications or insulin may benefit from meal planning to achieve carbohydrate consistency. Management of carbohydrate consumption and appropriate insulin adjustments for identified quantities of carbohydrate can improve glycemic control since carbohydrate intake directly determines postprandial blood glucose [36]. Older "conventional" insulin regimens, with fixed doses of short- and intermediate-acting insulins, require more consistency in timing and amounts of carbohydrate intake to avoid fluctuations in glucose values. However, flexible insulin dosing regimens, incorporating a long-acting insulin to provide basal levels and a rapid-acting insulin for premeal bolus doses, allow for adjustments of insulin dose for variations in carbohydrate intake. (See "General principles of insulin therapy in diabetes mellitus".)
Carbohydrate consistency may also be helpful for patients with erratic blood glucose patterns, including problems with hypoglycemia. In addition, reducing overall carbohydrate content at meals and snacks has been shown to improve glycemic control and can be applied in a variety of eating patterns [37]. Pre- and post-meal blood glucose monitoring data can then help to determine if adjustments to carbohydrate intake at meals and snacks will be sufficient, or if medication(s) need to be combined with MNT [1].
There are several meal planning approaches to achieve carbohydrate consistency. The selection of meal planning and whether to use carbohydrate counting (basic or advanced) is tailored to the individual.
●Basic carbohydrate counting – The goal of carbohydrate counting for patients with type 2 diabetes is to promote glycemic control by implementing a consistent pattern of carbohydrate consumption with meals and snacks. Patients who have been instructed in basic carbohydrate counting consume a predetermined total amount of carbohydrate proportioned throughout the day, calculated in grams of carbohydrate per food portion. The target amount of carbohydrate is usually based on nutrition goals and usual eating patterns. There is controversy about the optimal amount of carbohydrate consumption. (See 'Nutritional content' below.)
Patients need to be comfortable with simple arithmetic computations. Most patients will require specific training in carbohydrate counting, usually by a registered dietitian, to set an appropriate target and learn to measure or estimate portion size (table 4). (See "Nutritional considerations in type 1 diabetes mellitus", section on 'Basic carbohydrate counting'.)
For those who are not able to do basic carbohydrate counting, another option is to teach the diabetes plate method. This commonly used approach provides basic meal planning guidance and has been shown to help achieve improved glycemic control [38]. This method uses a simple graphic of a 9-inch plate to show how to portion foods (one-half plate as non-starchy vegetables, one-quarter plate as lean protein, and one-quarter plate for carbohydrates such as starches or grains). This balanced plate method is a viable option for those who have challenges with numeracy and food literacy or for those who need a simplified approach for achieving moderation of carbohydrate intake and better carbohydrate consistency [37].
●Advanced carbohydrate counting – At a more advanced level, carbohydrate counting focuses on adjustment of food, insulin, and activity based on patterns from detailed logs. Patients treated with flexible insulin dosing can determine how much rapid-acting insulin is needed to cover a certain amount of carbohydrate. Pre- and post-meal blood glucose monitoring data can help to determine if the insulin dose is correct. As an example, a patient may have been told to eat 60 grams of carbohydrate with their evening meal and precede this with 4 units of rapid-acting insulin. This means that they are using 1 unit to cover every 15 grams, and they can decrease their insulin dose proportionately if they plan to eat less carbohydrate at a meal. Facility with carbohydrate counting strategies becomes essential in making these adjustments.
Patients vary considerably in the amount of insulin required to cover a set amount of carbohydrate; some patients need a different insulin-to-carbohydrate ratio at different meals. Once the ratio is established, patients have freedom to vary the amount of carbohydrate ingested at particular meals. (See "Nutritional considerations in type 1 diabetes mellitus", section on 'Advanced carbohydrate counting'.)
Timing of food intake — Consistent timing of food intake is an important aspect of nutrition in type 2 diabetes patients treated with insulin secretagogues or traditional insulin regimens [36,39]. Insulin regimens that are based on the injection of roughly the same amount of insulin at the same time each day (twice-daily premix or basal plus oral medications) require some attention to consistency in meal timing. If meal time varies widely, then blood glucose profiles will fluctuate as well, with little chance of achieving low A1C values without a substantial risk of hypoglycemia. In contrast, basal-bolus insulin regimens offer patients with type 2 diabetes who require insulin more flexibility in meal timing. Meal timing consistency is also important for patients with type 2 diabetes who are taking oral medications that promote insulin secretion, such as sulfonylureas or meglitinides.
Nutritional content — The impact of specific dietary composition on weight change remains uncertain. When energy from dietary carbohydrates decreases, energy from fat or protein sources must increase. The reverse is also true; when energy from dietary fats decreases, energy from carbohydrate or protein sources increases. The debate has mainly centered on whether low-fat or low-carbohydrate diets can better induce weight loss and sustain it over the long-term. The relative importance of other dietary factors is also unknown; these include protein, types of fat, fiber (especially soluble), acid content of foods, particle size, food processing regimens, and rate and efficiency of digestion and absorption of different nutrients [40,41]. (See "Obesity in adults: Dietary therapy", section on 'Choosing a diet'.)
Macronutrient composition — The optimal macronutrient composition of the diet for patients with diabetes should be individualized based upon weight loss goals, other metabolic needs (eg, hypertension, dyslipidemia, nephropathy), and food preferences. A dietary pattern of healthful foods should be chosen, rather than focusing on a specific nutrient. Choosing a macronutrient mix based upon patient preferences may improve long-term adherence to the dietary prescription.
In patients with diabetes, there is not one ideal percentage of calories from carbohydrate, protein, and fat for all people [1]. In a systematic review of studies evaluating macronutrient composition in the management of patients with diabetes, several different dietary approaches with different macronutrient distributions improved glycemia and/or CVD risk factors [42].
●Mediterranean diet – A Mediterranean diet has been shown to improve glycemic control when compared with control diets (low fat, nonrestricted calorie, low carbohydrate, high carbohydrate, usual diet) [43].
As an example, in a four-year trial of a low-carbohydrate Mediterranean-style diet (≤50 percent complex carbohydrates, ≥30 percent mono- and polyunsaturated fat) versus a low-fat (<30 percent) diet in 215 overweight patients with newly-diagnosed type 2 diabetes, patients randomly assigned to the Mediterranean diet were less likely to require antihyperglycemic drugs (44 versus 70 percent) [44]. After one year, weight loss was greater in patients assigned to the Mediterranean diet (absolute difference 2 kg). However, there was no difference in weight loss between the two groups at years 3 and 4. Throughout the four years of the trial, the increase in HDL and decrease in triglycerides were significantly greater in the Mediterranean diet group. Following completion of the trial, all participants were invited to enter a previously unplanned monitoring program, which consisted of twice-yearly visits as participants continued to follow the assigned diet. At the end of eight years, the Mediterranean diet delayed the time to initiation of glucose-lowering medication (median 4.8 versus 2.8 years with the low-fat diet) [45].
The Mediterranean diet has also been shown to reduce the incidence of major cardiovascular events in patients at high risk for CVD, including those with diabetes [46]. (See "Prevention of cardiovascular disease events in those with established disease (secondary prevention) or at very high risk", section on 'Diet'.)
●Low-carbohydrate diet – Low-carbohydrate diets have been advocated by some and have demonstrated favorable outcomes (glycemic control, lipid lowering, and weight loss) in short-term studies [47-50]. Research studies on low-carbohydrate diets have generally noted challenges with long-term sustainability [51]. Therefore, it is important to reassess adherence abilities and individualize meal planning guidance as needed.
●Dietary fat – People with type 2 diabetes typically consume diets that are higher in total fat, saturated fat, and cholesterol than is recommended. Median intake of saturated fat is reported to be approximately 13 percent of calories, with 85 percent of persons exceeding the saturated fat recommendation of less than 10 percent [52]. Patients with diabetes who are consuming diets higher in fat must reduce saturated fat intake and also assure that their diet is adequate in sources of lean protein, fiber content, and essential vitamins and minerals. The type of fat consumed is critical for the prevention and treatment of CVD. Trans fat (hydrogenated fats) are atherogenic, while mono- and polyunsaturated fats (particularly omega-3 fatty acids) are protective. Different saturated fatty acids and different food sources of saturated fat have divergent effects on cardiovascular and metabolic health. There is some evidence that replacing saturated fat with polyunsaturated fat reduces fasting glucose, A1C, and insulin resistance and that replacing carbohydrates, saturated fat, or monounsaturated fat with polyunsaturated fat improves insulin secretion capacity [53]. (See "Dietary fat", section on 'Diabetes mellitus'.)
In one study, a diet high in monounsaturated fat was associated with a modestly lower blood pressure when compared with a high-carbohydrate diet [54].
Glycemic index and glycemic load — Foods containing the same amount of carbohydrate can have significantly different glycemic effects. In general, foods with higher fiber content have a lower glycemic index. These differences led to the development of the concepts of glycemic index and glycemic load. A more detailed discussion of the glycemic index is presented separately. (See "Nutritional considerations in type 1 diabetes mellitus", section on 'Glycemic index and glycemic load'.)
For patients with type 2 diabetes, low glycemic index diets may provide a modest benefit in terms of controlling postprandial hyperglycemia, especially in individuals previously consuming a high glycemic index diet [37,55]. However, in recent systematic reviews, low glycemic index diets in individuals with diabetes or at risk for diabetes had equivocal impact on A1C compared with other diets [1,5,56]. Increasing fiber intake preferably through food (vegetables, fruits, legumes, and intact whole grains) may help to modestly lower A1C and at the same time promote eating lower glycemic index foods [1,57].
Alcohol intake — Moderate amounts of alcohol, when ingested with food, do not significantly increase plasma glucose or serum insulin; however, the carbohydrate content of the non-alcohol component of a mixed drink may raise blood glucose. For patients who choose to ingest alcohol, intake should be limited to no more than one drink per day for women or two drinks per day for men. Alcohol should be consumed with food. For patients who need to lose weight, the excess calories from alcohol need to be considered.
Other supplements — Some minerals and nutritional supplements have purportedly improved glycemic control in patients with type 2 diabetes [58]. As an example, in some randomized trials, chromium supplementation improved glycemia among patients with diabetes but not among those with normal glucose tolerance [59]. However, there is insufficient evidence to recommend such supplements in patients who do not have underlying deficiencies. (See "Overview of dietary trace elements", section on 'Chromium'.)
Cinnamon supplementation has also been touted as a natural treatment for type 2 diabetes [60-66]. However, meta-analyses have shown conflicting results [67-70]. As an example, a meta-analysis of 10 clinical trials of cinnamon (Cinnamomum cassia, mean dose 2 g daily for 4 to 16 weeks) in patients with diabetes (predominantly type 2) did not show a significant beneficial effect of cinnamon on A1C, postprandial glucose, or serum insulin levels [67]. The effect of cinnamon on FBG levels was inconclusive due to significant heterogeneity among the point estimates. In contrast, another meta-analysis of eight trials found a significant lowering in FBG (-8.8 mg/dL [-0.49 mmol/L]) in patients with type 2 diabetes randomly assigned to cinnamon [68]. This meta-analysis was also limited by heterogeneity and the small sample size of the included trials. Thus, the available data are inadequate to provide any reliable conclusions regarding a beneficial effect of cinnamon.
Resveratrol is a naturally occurring antioxidant, a non-flavonoid phenol, found in red wine, mulberries, peanuts, rhubarb, and grapes. Although a range of claims about its health benefits have been made, a meta-analysis of three short-term trials did not show any benefit for A1C or fasting glucose [71].
DESIGNING A NUTRITION CARE PLAN — Although nutritional concerns in diabetes are often delegated to the dietitian, it is important for the general clinician to have a broad overview of the nutritional goals and of problems that may arise in attaining these goals. Ultimately, patients determine what they are willing or able to do to achieve improved glycemic control and prevention of diabetic complications.
Dietary history — The development of the nutrition care plan should begin by obtaining a dietary history, including:
●Dietary preferences
●Dietary content
●Patterns of physical activity
●Social support
●Education level
●Time constraints
●Other challenges
The dietary history, along with several days of food records, is helpful in an assessment of caloric intake and carbohydrate consistency. Recognizing that this is not always possible in the context of the clinician visit, a brief 24-hour recall will usually provide an assessment that will serve as a basis for initial changes and can be improved upon at follow-up visits.
Once sufficient data are obtained, changes can be advised to move the patient toward a more healthful diet. The patient's own food, activity, medication dosing and adherence, blood glucose records, and readiness to change can be helpful in guiding choices between a detailed exchange system, calorie and fat gram counting, use of meal replacements, a focus on carbohydrate counting, the diabetes plate method, or individualized behavioral goals; decisions between these options are made on an individual basis [72]. It is important to remember that the more marked the changes are from what the patient likes to eat, the less likely the patient is to comply with the dietary prescription [36]. (See 'Promoting dietary adherence' below.)
Dietary recommendations — We customize dietary recommendations to the patient's abilities and lifestyle, with changes centered on weight loss (when needed or desired), increased activity, day-to-day carbohydrate intake, and use of whole grains in preference to refined grains and starches. Meal timing at regular intervals for steady blood glucose control is most important for patients on insulin, sulfonylureas, or other secretagogues.
We agree with the American Diabetes Association (ADA) nutritional guidelines, which do not give specific total dietary compositional targets except for the following recommendations [1] that are in large part similar to the recommendations for the general population (see "Healthy diet in adults" and "Interactive diabetes case 18: A 61-year-old patient with type 2 diabetes and a recent change in diet (medical nutrition therapy)"):
●A diet that includes carbohydrates from fruits, vegetables, whole grains, legumes, and low-fat milk is encouraged.
The ideal amount of carbohydrate intake is uncertain. However, monitoring carbohydrate intake (carbohydrate counting or experience-based estimation) is important in patients with diabetes, as carbohydrate intake directly determines postprandial blood glucose, and appropriate insulin adjustment for identified quantities of carbohydrate is one of the most important factors that can improve glycemic control.
●A variety of eating patterns (Mediterranean, low fat, low carbohydrate, vegetarian) are acceptable.
●Fat quality is more important than fat quantity. Trans fats contribute to coronary heart disease, while mono- and polyunsaturated fats (eg, those found in fish, olive oil, nuts) are relatively protective. Saturated fatty acids and different food sources of saturated fat have divergent effects on cardiovascular and metabolic health. Trans fatty acid consumption should be kept as low as possible.
●Protein intake goals should be individualized and should be approximately 0.8 g/kg body weight per day (the recommended daily allowance). Patients should be encouraged to substitute lean meats, fish, eggs, beans, peas, soy products, and nuts and seeds for red meat. Higher levels of dietary protein intake (>20 percent of calories from protein or >1.3 g/kg/day) have been associated with increased albuminuria, more rapid kidney function loss, and cardiovascular disease (CVD) mortality and therefore should be avoided [73].
An automatic reduction of dietary protein intake below usual protein intake of 15 to 20 percent of total calories in patients who develop diabetic kidney disease is not recommended [73]. The role of dietary protein restriction is uncertain, particularly in view of problems with compliance in patients already being treated with saturated fat and simple carbohydrate restriction. Furthermore, it is uncertain if a low-protein diet is significantly additive to other measures aimed at reducing cardiovascular risk and preserving renal function, such as angiotensin-converting enzyme (ACE) inhibition and aggressive control of blood pressure and blood glucose.
●Fiber intake should be at least 14 grams per 1000 calories daily; higher fiber intake may improve glycemic control.
●A reduced sodium intake of 2300 mg per day with a diet high in fruits, vegetables, and low-fat dairy products is prudent and has demonstrated beneficial effects on blood pressure.
●Sugar-sweetened beverages should be avoided in order to control glycemia, weight, and reduce risk for CVD and fatty liver. Consumption of foods with added sugar that have the capacity to displace healthier, more nutrient-dense food choices should be minimized. Care should be taken to avoid excess calories from sucrose; however, foods containing sucrose may be substituted for other carbohydrates or covered with insulin or insulin secretagogue medications.
●Sugar alcohols and non-nutritive sweeteners are safe when consumed within daily levels established by the US Food and Drug Administration (FDA). When calculating carbohydrate content of foods, one-half of the sugar alcohol content can be counted in the total carbohydrate content of the food. Use of sugar alcohols needs to be balanced with their potential to cause gastrointestinal side effects in sensitive individuals.
Promoting dietary adherence — Motivating a patient to make a long-term commitment to dietary alterations is a challenge. Achieving and maintaining weight reduction is difficult in any patient with type 2 diabetes and overweight or obesity; however, insulin users may have more difficulty losing weight than non-insulin users [20]. Dietary adherence is a major factor in achieving glycemic control in type 2 diabetes.
Adherence may be enhanced by the following:
●Engaging in person-centered collaborative care that is guided by shared decision-making in treatment selection and monitoring of an individualized nutrition care plan that incorporates and is respectful of the individual preferences, needs, goals, values, and life experiences of the person with diabetes [37].
●Perform nutrition education in a setting where real food can be used, so that the patient can become familiar with household measures and can improve his or her ability to estimate the calorie, fat, or carbohydrate content of foods commonly eaten. This is often best accomplished in dietary workshops for small groups of patients [74].
●Emphasize the rapid and often dramatic improvement in glycemic control induced by the combination of caloric restriction and initial weight reduction [2,11,12]. Adherence to intensive dietary therapy may be associated with a reduction in comorbidities (including diabetes remission) and mortality, which may provide further motivation to the patient [75].
●During follow-up visits, ask specifically about diet and exercise to reinforce their importance. Ideally, a patient should be able to quote his or her dietary and exercise prescription in detail. Patients requiring insulin and using carbohydrate counting will also need to be able to specify how many grams of carbohydrate they aim to eat at each meal and snack during the day.
Periodic adjustments are necessary in the patient's comprehensive plan for diet, exercise, stress, and pharmacologic interventions to achieve and maintain glycemic control and prevent complications. The four critical times for providers to make medical nutrition therapy (MNT) referrals are at diagnosis; annually and/or when not meeting treatment targets; when medical, physical, or psychological complicating factors develop; and when transitions in life and care occur [76]. The clinician needs to maintain awareness of the patient's changing life circumstances, motivation, and lifestyle patterns and help the patient make adaptations in their plan accordingly.
Many patient factors influence the likelihood of successful dietary intervention. The following observations have been made concerning the likelihood of inducing and maintaining weight loss:
●Exercise can increase the degree of weight loss and the likelihood that it will be maintained. In one study of 74 patients, as an example, the patients who maintained weight loss were more likely to exercise (90 versus 34 percent) [77]. (See "Exercise guidance in adults with diabetes mellitus".)
●Self-monitoring for weight and dietary intake, in conjunction with goal setting and individualized problem-solving, can be helpful in achieving and maintaining weight loss [78]. Patients who were more successful with weight loss were conscious of their eating behaviors (70 versus 30 percent), used available social supports (70 versus 38 percent), and confronted problems directly (90 versus 10 percent) [77].
●Patients who refuse food when offered by others and are able to stop eating when appropriate are more likely to maintain weight loss and achieve glycemic control [79].
●Providing structured meal plans and grocery lists is very effective, but no additional benefit appears to be obtained by providing the actual food (even if free) or giving financial incentives to lose weight [27,80].
Other education
Hypoglycemia — Patients taking insulin or oral hypoglycemic medications that increase insulin secretion should be well trained in methods to treat hypoglycemia, for example during or after exercise, to prevent overcompensation. A pattern of overtreating hypoglycemia can result in a greater than desired rise in blood glucose and increased calorie intake, resulting in weight gain. In the long-term, it is better to adjust medications or insulin to compensate for increased activity (or a reduced calorie intake) rather than add extra snacks in patients with type 2 diabetes, as most are trying to lose weight or manage weight. (See "Hypoglycemia in adults with diabetes mellitus".)
●Advise patients to carry a snack with 10 to 15 grams of carbohydrate (table 5) to prevent hypoglycemia or to treat hypoglycemia.
●For blood glucose of 51 to 70 mg/dL, treat with 10 to 15 g of fast-acting carbohydrate.
●For blood glucose ≤50 mg/dL, treat with 20 to 30 g of fast-acting carbohydrate.
●Retest 15 minutes after ingestion and repeat treatment as needed based on blood glucose levels.
●Once blood glucose is >70 mg/dL, the patient should use the appropriate insulin dose to cover carbohydrate intake at the meal. If the meal following the hypoglycemic episode is going to be delayed, a snack containing another 15 grams of carbohydrate should be consumed.
Weight consequences of diabetes medications — Weight gain is an adverse effect of many medications used to manage glucose in diabetes, including insulin and many oral agents [81]. In particular, the patient about to begin intensive insulin therapy must be cautioned about the potential to gain weight and the need for weight monitoring.
In one study, the average weight gain in patients with type 2 diabetes treated with an insulin regimen was 8.7 kg [82]. In the United Kingdom Prospective Diabetes Study (UKPDS), the average weight gain after 10 years of insulin therapy was approximately 7 kg for patients with type 2 diabetes, with the most rapid weight gain occurring when insulin was first initiated [83]. Less intensive therapy with either insulin or a sulfonylurea (which increases endogenous insulin secretion) was associated with a 3.5 to 4.8 kg weight gain at three years versus no change with metformin monotherapy [84].
Thiazolidinedione therapy (pioglitazone and rosiglitazone) is associated with significant weight gain. It is both dose dependent and time dependent, and it can be substantial. Some weight gain from thiazolidinediones may be associated with fluid retention, which is of significant concern in patients with congestive heart disease. This topic is reviewed in detail elsewhere. (See "Thiazolidinediones in the treatment of type 2 diabetes mellitus", section on 'Weight gain'.)
In contrast, the use of glucagon-like peptide-1 (GLP-1) agonists and sodium-glucose co-transporter 2 (SGLT2) inhibitors are associated with moderate weight loss [85]. Metformin and dipeptidyl peptidase-4 (DPP-4) inhibitors are generally weight neutral. (See "Initial management of hyperglycemia in adults with type 2 diabetes mellitus" and "Management of persistent hyperglycemia in type 2 diabetes mellitus" and "Glucagon-like peptide 1-based therapies for the treatment of type 2 diabetes mellitus", section on 'Weight loss'.)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Diabetes mellitus in adults" and "Society guideline links: Diabetes mellitus in children".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Type 2 diabetes (The Basics)" and "Patient education: Diabetes and diet (The Basics)" and "Patient education: Carb counting for adults with diabetes (The Basics)")
●Beyond the Basics topics (see "Patient education: Type 2 diabetes: Overview (Beyond the Basics)" and "Patient education: Type 2 diabetes and diet (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Medical nutrition therapy plan – The medical nutrition therapy (MNT) plan is the process by which a registered dietitian-nutritionist (RDN) tailors a meal planning approach for people with diabetes based on medical, lifestyle, and personal factors. It is an integral component of diabetes management and diabetes self-management education. The five components of MNT are weight management and physical activity, caloric intake, day-to-day carbohydrate consistency, nutritional content, and meal timing. (See 'Definition' above.)
The MNT for patients with type 2 diabetes should optimally manage the "ABCs" of diabetes control: glycated hemoglobin (A1C), blood pressure, and low-density lipoprotein (LDL) cholesterol. The nutrition care plan must be tailored for the individual patient to further address existing or at-risk complications related to diabetes or other concomitant conditions. (See 'Goals' above.)
●Weight management – Major emphasis should be placed on the benefits of lowering caloric intake and inducing weight loss for patients with type 2 diabetes and overweight (body mass index [BMI] ≥25 to 29.9 kg/m2) and obesity (BMI ≥30 kg/m2). A sustained weight loss of even 5 to 10 percent of initial body weight in can have a lasting beneficial impact on serum glucose, dyslipidemia, and hypertension. (See 'Weight management' above.)
Physical activity, diet, and behavioral modification are important components of all programs to accomplish weight loss. There are additional options for weight loss, including addition of medication to promote weight loss and bariatric surgery. (See 'Weight loss strategies' above and "Obesity in adults: Overview of management".)
●Nutritional counseling for all patients
•Carbohydrate consistency – Although patients with type 2 diabetes are more resistant to hypoglycemia than patients with type 1 diabetes, patients who are treated with hypoglycemic medications or insulin may benefit from meal planning to achieve carbohydrate consistency. Carbohydrate consistency may also be helpful for patients with erratic blood glucose patterns, including problems with hypoglycemia. In addition, reducing overall carbohydrate content at meals and snacks has been shown to improve glycemic control and can be applied in a variety of eating patterns. (See 'Carbohydrate consistency' above.)
•Meal timing – Consistent timing of food intake is an important aspect of nutrition in type 2 diabetes patients treated with insulin secretagogues or traditional insulin regimens. If meal time varies widely, then blood glucose profiles will fluctuate as well, with little chance of achieving low A1C values without a substantial risk of hypoglycemia. (See 'Timing of food intake' above.)
•Macronutrient composition – The impact of specific dietary composition on glycemic control and cardiovascular risk remains uncertain. The optimal macronutrient composition of the diet for patients with diabetes should be individualized, based upon weight loss goals, other metabolic needs (eg, hypertension, dyslipidemia, nephropathy), and food preferences. A diet that includes carbohydrates from fruits, vegetables, whole grains, legumes, and low-fat milk is encouraged. It is important to distinguish between types of fat in the diet, lowering saturated and avoiding hydrogenated fats, while consistently including monounsaturated and omega-3 fatty acids in the diet. Protein intake should be appropriate to medical condition. (See 'Nutritional content' above and 'Dietary recommendations' above.)
●Promoting adherence – Adherence can be fostered by engaging in person-centered collaborative care that is guided by shared decision-making in treatment selection and monitoring of an individualized nutrition care plan that incorporates and is respectful of the individual preferences, needs, goals, values, and life experiences of the person with diabetes. (See 'Promoting dietary adherence' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges David McCulloch, MD, who contributed to earlier versions of this topic review.
