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Nutritional considerations in type 1 diabetes mellitus

Nutritional considerations in type 1 diabetes mellitus
Linda M Delahanty, MS, RD
Ruth S Weinstock, MD, PhD
Section Editors:
Irl B Hirsch, MD
David Seres, MD
Deputy Editor:
Katya Rubinow, MD
Literature review current through: Dec 2022. | This topic last updated: Dec 14, 2022.

INTRODUCTION — Diet and physical activity are critically important in the treatment of type 1 diabetes. Basic principles of nutritional management, however, are often poorly understood by both clinicians and people with type 1 diabetes.

The nutrition prescription for adults with type 1 diabetes should aim to optimally address the "ABCs" of diabetes management: glycemia as measured by glycated hemoglobin (A1C) and glucose monitoring, blood pressure, and low-density lipoprotein (LDL) cholesterol. The prescription must also be tailored for the individual to address diabetes complications and other concomitant conditions.

The role of nutrition and the development of a medical nutrition therapy (MNT) plan for a person with type 1 diabetes are discussed here. Nutritional considerations for people with type 2 diabetes, dietary counseling for celiac disease, and the insulin management for type 1 diabetes are discussed separately. (See "Nutritional considerations in type 2 diabetes mellitus" and "Management of blood glucose in adults with type 1 diabetes mellitus" and "Management of celiac disease in adults", section on 'Dietary counseling'.)

NUTRITIONAL GOALS — The nutritional goals for people with type 1 diabetes are to:

Maintain as near-normal blood glucose levels as possible, by integrating insulin therapy into each individual's diet and physical activity patterns.

Achieve optimal blood pressure and lipid levels.

Provide adequate calories for achieving and maintaining a reasonable body weight, normal growth, and development.

Manage other comorbid conditions such as hypertension, hyperlipidemia, and renal, cardiovascular, and celiac disease.

Prevent complications of diabetes, both acute (hypoglycemia and ketoacidosis) and chronic (micro- and macrovascular complications).

Improve overall health through healthful food choices.

Address individual nutrition needs, incorporating personal and cultural preferences, willingness to change, and maintaining the pleasure of eating by restricting choice only when clearly appropriate.

The relative importance of each nutritional goal varies with the individual.

MEDICAL NUTRITION THERAPY — Medical nutrition therapy (MNT) is the process by which the nutrition prescription is customized for each individual based on medical, lifestyle, and personal factors. It is an integral component of diabetes management and diabetes self-management education [1].

Randomized trials of MNT in people with type 1 diabetes have demonstrated decreases in A1C of up to 1.9 percentage points from baseline in three to six months [1,2]. In the Diabetes Control and Complications Trial (DCCT), the following specific diet behaviors were associated with achieving up to a 1 point lower mean A1C (7 versus 8 percent) [2]:

Adherence to the negotiated meal plan (diet consistency)

Adjusting food and/or insulin in response to hyperglycemia

Adjusting insulin dose for meal size and content

Appropriate treatment of hypoglycemia (not overtreating hypoglycemia)

Consistent habits with regard to consumption of a bedtime snack and avoidance of extra nighttime snacks

Proper attention to diet is a major factor in minimizing hypoglycemia and weight gain while achieving glycemic goals [2-5]. Glycemic management has been shown to markedly diminish the likelihood of neuropathy, nephropathy, retinopathy, and coronary artery disease in people with type 1 diabetes [6,7]. (See "Glycemic control and vascular complications in type 1 diabetes mellitus".)

MNT for type 1 diabetes integrates:

Personal dietary preferences

Consistency in day-to-day carbohydrate intake

Dosing insulin for variations in blood glucose, food, and activity

Weight management

Nutritional content (balance of selected protein, quality carbohydrates, and fats)

Meal-insulin timing

Carbohydrate counting is important for people with type 1 diabetes who generally adjust their mealtime insulin based on carbohydrate content [8]. For adults with the ability to take additional steps to manage diabetes and prevent complications, learning to adjust insulin doses for variations in fat and protein intake or changes in activity will also be beneficial [9-13]. (See 'Advanced carbohydrate counting' below and 'Adjustments for high fat or protein meals' below and "Exercise guidance in adults with diabetes mellitus", section on 'Glycemic management during exercise'.)

CARBOHYDRATE CONSISTENCY — Variations in food intake, particularly carbohydrate intake, can result in erratic blood glucose levels and hypoglycemia in people with type 1 diabetes. Intensive insulin regimens, which combine basal insulin with boluses or injections of rapid-acting pre-meal insulins, allow for some flexibility in the carbohydrate content of meals. In one study of people receiving intensive insulin therapy, as an example, the total amount of carbohydrate in the meal did not influence glycemic response if pre-meal insulin was adjusted for variations in the carbohydrate content of the meal [14]. People who use rapid-acting insulin analogs by injection or via an insulin pump may need to take additional bolus insulin with snacks that contain carbohydrates.

For people receiving fixed doses of insulin, however, day-to-day consistency in the amount of carbohydrate and source of carbohydrate at meals and snacks is especially important. Carbohydrate consistency for these individuals has been associated with lower A1C levels, whereas day-to-day variations in calorie, protein, or fat intakes were not significantly related to A1C [15].

Meal planning — There are several meal planning approaches to achieve carbohydrate consistency, including basic and advanced carbohydrate counting, the exchange system, and sample menus. The best approach for an individual is determined by an assessment of their lifestyle and learning capabilities.

Basic carbohydrate counting — In its simplest form, the goal of basic carbohydrate counting is to support glycemic management by implementing a consistent pattern of carbohydrate consumption with meals and snacks day to day. Since carbohydrate intake directly determines postprandial blood glucose, management of carbohydrate consumption and appropriate insulin adjustments for identified quantities of carbohydrate can improve glycemia [16].

People with diabetes who have been instructed in carbohydrate consistency consume a predetermined total amount of carbohydrate at meals and snacks each day, calculated in grams of carbohydrate per food portion. The calculated carbohydrate intake is derived from an optimal percentage of total calories from carbohydrates, based on nutrition goals and the usual eating pattern.

The person with type 1 diabetes needs to be comfortable with simple arithmetic computations. Most people will require specific training in carbohydrate counting, if possible by a registered dietitian, to set appropriate meal and snack targets and learn to measure or estimate portion sizes and read food labels (table 1).

Exchange system — 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 [17]. 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 [17].

The exchange system meal planning approach can be used as a tool to help people achieve calorie, fat, and carbohydrate goals. However, many individuals find that it is a complicated system to learn.

Sample menus — Sample menus are defined meal menus that specify the time and amounts of food to be eaten at each meal and snack. For people with type 1 diabetes, menus are developed to meet calorie needs and provide consistent carbohydrate intake at meals and snacks. Dietitians typically tailor the menus to incorporate food preferences and medical nutrition therapy (MNT) goals. Sample menus are created after review of a person's typical food intake; they are best suited for people who have fairly routine eating habits and who do not eat a wide variety of foods. They also are appropriate for people who need structured guidance on what to eat.

Insulin dosing

Advanced carbohydrate counting — At a more advanced level, carbohydrate counting focuses on adjustment of insulin dosing based on anticipated carbohydrate intake. There are different methods that can be used to calculate the insulin-to-carbohydrate ratio [17]. Calculating the ratio based on individually recorded data is more accurate than estimating it using the 450 to 500 rule.

Individually recorded data – When initiating advanced carbohydrate counting, it is helpful to log food intake, insulin doses, and activity. The individual is asked to record time of meals and snacks, the amount and type of food eaten, amount of carbohydrate consumed, insulin doses, physical activity, and glucose monitoring results. People should first practice eating usual amounts of carbohydrate at meals and snacks so that baseline insulin requirements can be matched to the carbohydrate intake using pre- and postprandial glucose testing results. When pre- and postprandial glucose levels are in the target range, then insulin-to-carbohydrate ratios can be determined as follows:

Divide the number of grams of carbohydrate eaten at the meal by the number of units of pre-meal insulin (eg, 45 g carbohydrate divided by 3 units of insulin is a 1:15 ratio). Insulin-to-carbohydrate ratios can vary with time of day and are affected by stress, illness, and variations in physical activity.

450 to 500 rule – Calculate the insulin-to-carbohydrate ratio as follows:

Regular insulin-to-carbohydrate ratio = 450 divided by total daily dose (TDD) of insulin.

Rapid-acting insulin-to-carbohydrate ratio = 500 divided by TDD of insulin.

As an example, if the TDD is 50 units and the person uses a regimen with rapid-acting insulin, then each unit of insulin should cover approximately 10 g of carbohydrate (500 divided by 50 = 10). The insulin-to-carbohydrate ratio is 1:10.

Adjustments for high fat or protein meals — When consuming high amounts of fat and protein, estimating insulin dosing based only on the carbohydrate content of the meal will be insufficient for many individuals with type 1 diabetes. The amount of dietary fat and protein in a meal can significantly affect glycemic excursions and insulin dosing, as illustrated by the following trials [9-13]:

In a trial in adults with type 1 diabetes, individuals consumed 45 g of carbohydrate with 0, 20, 40, or 60 g fat [9]. The higher fat content meals significantly reduced early (1 to 2 hour) postprandial glycemia and increased late (3 to 5 hour) postprandial glycemia, irrespective of the type of fat added (saturated, monounsaturated, or polyunsaturated). With higher fat meals, dual-wave insulin boluses, with larger amounts of insulin delivered in the late postprandial interval, improved glycemia.

In a trial in 11 adolescents with type 1 diabetes, individuals consumed 30 g of carbohydrate, 8 g of fat, and either 60 or 5 g of protein [10]. Over the subsequent five hours, the higher-protein meal required more insulin than the lower-protein meal to maintain euglycemia (10.3 versus 6.7 units).

In another randomized trial in 10 adolescents or young adults with type 1 diabetes, individuals were randomly assigned to receive a high-protein (60 g), high-fat (40 g) meal versus a low-protein (5 g), low-fat (5 g) meal [13]. Both meals contained 30 g of carbohydrate. Insulin requirements over the next five hours were almost twice as high with the high-protein, high-fat meal (11 versus 5.7 units).

Adjustments for elevated glucose — An insulin correction factor can be used to adjust insulin dose for hyperglycemia before or between meals. To calculate the insulin correction factor:

For regular insulin, divide 1500 by TDD

For rapid-acting insulin, divide 1800 by TDD

As an example, if a person using rapid-acting insulin has a TDD of 45 units, then the insulin correction factor would be 1 unit for every 40 mg/dL reduction in blood glucose (1800 divided by 45). If the person had a pre-meal glucose of 180 mg/dL and wanted to correct to a pre-meal glucose of 100 mg/dL, then the person would take an extra 2 units of rapid-acting insulin to correct to the target of 100 mg/dL and add the number of units needed to cover the carbohydrates consumed.

Treatment of hypoglycemia — A person with hypoglycemia (blood glucose <70 mg/dL) should treat the hypoglycemia with 10 to 15 g of fast-acting carbohydrate for glucose levels of 51 to 70 mg/dL and with 20 to 30 g of fast-acting carbohydrate for blood glucose levels ≤50 mg/dL. They should then retest 15 minutes after ingestion and repeat treatment as needed based on glucose levels. Once blood glucose is >70 mg/dL, the person 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. A pattern of overtreating hypoglycemia can result in a greater-than-desired rise in blood glucose and increased calorie intake, resulting in weight gain.

PHYSICAL ACTIVITY/EXERCISE — Exercise is a significant component of diabetes management. Benefits of exercise include improved glycemia, weight management, reduction in comorbidities (hypertension, dyslipidemia, and cardiovascular disease), improved mood, and quality of life. We encourage most adults with diabetes to perform at least 150 minutes of moderate-intensity aerobic exercise per week (30 to 60 minutes on most days of the week). A shorter duration of more vigorous aerobic exercise (75 minutes per week of jogging 9.6 km/hour) is an alternative for physically fit individuals who have been regularly exercising. People with comorbid conditions should discuss an appropriate exercise regimen with their health care providers. (See "Exercise guidance in adults with diabetes mellitus", section on 'Evaluation prior to recommending an exercise regimen'.)

The timing of exercise in relation to insulin dose, type, mode of delivery, and time of injection should be considered. People with diabetes should check glucose levels before and after exercising, especially in the beginning of an exercise program, to evaluate their glycemic response to exercise and to adjust insulin and carbohydrate regimens, as needed, to prevent hypoglycemia. Adults who learn to self-adjust their diet or insulin to accommodate exercise can achieve near-normal A1C levels without undue hypoglycemia. For people who are trying to lose weight, it is preferable to adjust insulin doses rather than increase food intake to compensate for exercise. Glycemic management during exercise is reviewed in more detail separately. (See "Exercise guidance in adults with diabetes mellitus", section on 'Glycemic management during exercise'.)


Optimal body weight — Body mass index (BMI) is commonly used to classify weight status and is calculated as: [weight in kg ÷ (height in m)2]. Optimal body weight is a BMI ≥18.5 and 24.9 kg/m2 (calculator 1). A BMI of <18.5 kg/m2 is considered underweight, 25.0 to 29.9 kg/m2 overweight, and ≥30 kg/m2 obese. (See "Obesity in adults: Prevalence, screening, and evaluation", section on 'Body mass index'.)

BMI is a good but imperfect indicator of body fat. For example, some athletes may have a relatively high BMI due to high muscle mass. The use of BMI also has limitations in the older adult population, who may have a low muscle mass and fluid retention.

Caloric intake — The relative importance of caloric intake for an individual is dependent on several factors, including:

Current weight in relationship to desirable and healthy body weight

Weight history

Fat distribution and waist circumference

Muscle mass



Lowering caloric intake and inducing weight loss are of major importance for adults with type 1 diabetes who have overweight (BMI ≥25 to 29.9 kg/m2) or obesity (BMI ≥30 kg/m2) since the risk of comorbidities associated with excess adipose tissue increases with BMI in these ranges. The presence of obesity, in particular, can worsen insulin resistance and increase risk of cardiovascular disease, stroke, retinopathy, and nephropathy [1,18,19].

If an individual with type 1 diabetes has been close to ideal body weight for several years and has a near normal A1C, then their current caloric intake is most likely appropriate.

Estimating caloric intake for weight maintenance — Several formulas are available to estimate baseline caloric intake for weight maintenance. When using any of these formulas, it is important to keep in mind that there is individual variability as well as variability related to age, sex, ethnicity, BMI, and activity [20-22]. Older, sedentary individuals with obesity have lower resting metabolic rates. The ingestion of caffeine and other stimulants as well as use of nicotine-containing products can raise the resting metabolic rate [23].

An easy-to-use calorie calculator for roughly estimating caloric intake associated with weight maintenance uses the patient's age, sex, height, weight, and usual level of physical activity.

To estimate caloric needs for weight loss of 1 to 2 pounds per week, subtract 500 to 1000 calories per day from weight maintenance calories (see "Obesity in adults: Dietary therapy", section on 'Rate of weight loss'). 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.

Weight gain with intensive therapy — Weight gain is a potential adverse effect of intensive diabetes therapy in type 1 diabetes, and it occurs when insulin dosing matches nutritional intake (particularly when excess calories are ingested) and glycosuria is eliminated [24,25]. Additional possible contributions to weight gain include genetic factors, sedentary lifestyle, stress, psychosocial factors, peripheral hyperinsulinemia with associated increases in peripheral fat mass, and changes in growth hormone/insulin-like growth factor 1 (IGF-1) [18]. The mean increase in weight in patients in the Diabetes Control and Complications Trial (DCCT) was 5.1 kg in the intensive therapy group and 2.4 kg in the conventional therapy group [25]. At study end, 33 percent of the intensive therapy group was overweight compared with 19 percent of the conventional treatment group [26]. The DCCT was performed before the availability of insulin analogs, continuous glucose monitors (CGM), and hybrid closed-loop systems.

If blood glucose is high enough to promote glycosuria, then lowering calorie intake by an additional 250 to 300 calories per day is necessary to prevent weight gain with intensification of diabetes therapy [3]. Other strategies to minimize weight gain with intensive therapy are to reduce insulin doses preferentially for patterns of hypoglycemia rather than increasing meal size or adding an undesired snack. To reduce calories further, it is helpful to reduce fat intake and try to keep carbohydrate intake consistent to minimize risk of hypoglycemia.

Weight gain is most prominent in women, especially those with high A1C values at baseline, and has been a cause of nonadherence with insulin therapy. As examples, approximately 30 percent of women with type 1 diabetes in one study occasionally omitted insulin injections intentionally [27]; in a second study, 9 percent did so on a regular basis in order to avoid weight gain [28]. (See 'Eating disorders' below.)


Macronutrient composition — The macronutrient composition of the diet should be individualized based on metabolic goals and patient preferences [8]. We largely agree with the American Diabetes Association (ADA) nutritional guidelines as follows [8]:

A variety of eating patterns (low fat, low carbohydrate, Mediterranean, vegetarian) are acceptable.

A diet that includes carbohydrates from fruits, nonstarchy vegetables, whole grains, legumes, and dairy products with minimally added sugars is encouraged.

The ideal amount of carbohydrate intake is uncertain, although avoiding high carbohydrate intake can improve glycemia [29]. Monitoring carbohydrate intake (basic or advanced carbohydrate counting) is important for people with type 1 diabetes as carbohydrate intake directly affects postprandial blood glucose. Appropriate insulin adjustment for identified quantities of carbohydrate is one of the most important factors that can improve glycemia (see 'Advanced carbohydrate counting' above). Sugar-sweetened beverages should be avoided in order to manage glycemia, weight, and to reduce risk for cardiovascular disease and fatty liver.

If using very low-carbohydrate ketogenic diets, safety concerns include increased risk of developing diabetic ketoacidosis, hypoglycemia, and dyslipidemia [30]. A continuous glucose monitor (CGM) and ketone testing should be utilized, and the person with diabetes should understand the signs and symptoms of diabetic ketoacidosis.

Saturated fat and trans fat contribute to coronary heart disease, while mono- and polyunsaturated fats are relatively protective. Saturated fats (eg, in meats, cheese, ice cream) can be replaced with mono- and polyunsaturated fatty acids (eg, in fish, olive oil, nuts). Trans fatty acid consumption should be kept as low as possible. High-fat diets are associated with greater insulin requirements. (See 'Adjustments for high fat or protein meals' above.)

Protein intake goals should be individualized but not lower than 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.

An automatic reduction of dietary protein intake (eg, 15 to 19 percent of calories) below usual protein intake in patients who develop diabetic kidney disease is not recommended. The role of dietary protein restriction is uncertain, particularly in view of problems with adherence in people 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.

The usual daily intake of protein should be approximately 15 to 20 percent of total caloric intake. 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 mortality and therefore should be avoided [31]. High-protein diets are also associated with greater insulin requirements. (See 'Adjustments for high fat or protein meals' above.)

Fiber intake should be at least 14 grams per 1000 calories daily. Meeting the fiber intake recommendations through food (vegetables, legumes, fruits, and whole intact grains), as compared with dietary supplementation, is encouraged for the additional benefits of coexisting micronutrients and phytochemicals.

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 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.

Consumption of foods with added sugar that have the capacity to displace healthier, more nutrient-dense food choices should be minimized [8,32]. Care should be taken to avoid excess calories from sucrose; however, sucrose can be substituted for other carbohydrate sources in the meal plan or, if added, covered with insulin. Use of added fructose as a sweetener is not recommended, as it may adversely affect lipids, but there is no need to avoid fructose occurring naturally in fruits and vegetables.

The relative importance of other dietary factors is uncertain; these include soluble fiber, acid content of foods, particle size, food processing regimens, and rate and efficiency of digestion and absorption of different nutrients [33,34]. There is also no clear evidence of benefit from vitamin and mineral supplementation in people with diabetes who do not have underlying deficiencies [8].

People with type 1 diabetes typically consume more saturated fat than is recommended [35-37]. Among intensively treated patients with type 1 diabetes in the Diabetes Control and Complications Trial (DCCT), saturated fat intake was close to 13 percent of calories during the trial and diets higher in total and saturated fat and lower in carbohydrate were associated with worse glycemic control independent of exercise and body mass index (BMI) [35]. In a subsequent review of observational studies evaluating dietary intake and compliance with nutrition recommendations in adults with type 1 diabetes, mean saturated fat intake exceeded recommendations and less than one-third followed the guidelines to limit saturated fat to <10 percent of calories [37].

Glycemic index and glycemic load — Foods containing the same amount of carbohydrate can have significantly different glycemic effects. These differences led to the development of the concepts of glycemic index and glycemic load:

Glycemic index is an in vivo measure of the relative impact of carbohydrate-containing foods on blood glucose. A particular food's glycemic index is determined by evaluating the incremental rise in blood glucose after ingestion of a portion of the test food containing 50 g of carbohydrate, compared with the same amount of carbohydrate from a reference food, which is usually white bread or glucose [38,39]. Some examples of low glycemic index foods include non-starchy vegetables, nuts, legumes, and certain grains such as barley and converted rice. High glycemic index foods include potatoes, candies, white bread, and other refined products made from grains.

Glycemic load is the product of the glycemic index value of a food and its total carbohydrate content [40,41]. The concept of the glycemic load was developed because the blood glucose response is influenced not only by the quality of the carbohydrate consumed (ie, the glycemic index), but also by the quantity of carbohydrate consumed.

In systematic reviews and randomized trials, low glycemic index diets in individuals with type 1 diabetes or at risk for diabetes had equivocal impact on A1C compared with other diets, leading to uncertainty in their utility over other diets in clinical care [42-45].

Increasing fiber intake preferably through food (vegetables, fruits, legumes, and intact whole grains) may help in modestly lowering A1C and at the same time will promote eating lower glycemic index foods. Observational studies (eg, The European Diabetes Centers [EURODIAB] Prospective Complications Study and the Coronary Artery Calcification in Type 1 Diabetes (CACTI) study) showed an inverse association between fiber intake and A1C in adults with type 1 diabetes [46,47].

Alcohol intake — Acute and/or delayed hypoglycemia have been reported with alcohol consumption [8,48]. Moderate amounts of alcohol, when ingested with food, do not significantly increase plasma glucose or serum insulin; however, the carbohydrate content of the nonalcohol component of a mixed drink may raise blood glucose. It is generally recommended that if people choose to ingest alcohol, they limit their intake to no more than one drink per day for women or two drinks per day for men; alcohol should be consumed with food [1]. Adults with type 1 diabetes should use glucose monitoring to assess any immediate or delayed effects of alcohol intake on glucose levels.

MEAL-INSULIN TIMING — In people receiving fixed doses of short- and intermediate-acting insulins, meal timing at regular intervals is important for attaining glycemic goals and avoiding hypoglycemia [2,16,49]. If the amount and timing of carbohydrate intake varies widely, blood glucose profiles fluctuate, with little chance of achieving target A1C values without a substantial risk of hypoglycemia. Insulin analogs mitigate this risk somewhat and allow for more flexibility in meal schedules and content. (See "Management of blood glucose in adults with type 1 diabetes mellitus" and "Cases illustrating problems with insulin therapy for type 1 diabetes mellitus", section on 'Case 1: Glycemic variability due to diet'.)

An alternative approach to a fixed mealtime and carbohydrate intake is to determine how much short- or rapid-acting insulin is needed to cover a certain amount of carbohydrate. People vary considerably in the amount of insulin required to cover a set amount of carbohydrate; some adults need a different carbohydrate-to-insulin ratio at different meals. Once the ratio is established, people with type 1 diabetes have flexibility to vary the amount of carbohydrate ingested at particular meals. (See 'Advanced carbohydrate counting' above.)

As an example, a person may have been told to eat 60 g 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 g of carbohydrate and can decrease their insulin dose proportionately if they plan to eat less carbohydrate at a meal. Facility with carbohydrate counting strategies is important in making these adjustments.

EATING DISORDERS — Eating disorders are relatively common in people with diabetes, especially in female adolescents and young adults with type 1 diabetes [50]. Eating disorders have a deleterious impact on glycemic control and on long-term outcomes. One study evaluated 91 females with type 1 diabetes (mean age 15 years) at baseline and at follow-up four to five years later [51]. The following findings were noted:

Twenty-six (29 percent) had a self-reported eating disorder at baseline, which persisted in 16 (18 percent) at follow-up.

Among the patients with normal eating patterns at baseline, 15 percent had disordered eating at follow-up.

Dieting and binge eating were the most common eating disorders.

Disordered eating was associated with adverse outcomes [51,52]. At baseline, A1C values were significantly higher in those with highly disordered eating than in those with moderately disordered or normal eating (11.1 versus 8.9 and 8.7 percent, respectively). People with eating disorders were more likely to have retinopathy at follow-up.

It is important to evaluate people with type 1 diabetes, especially young women, for an eating disorder as well as for omission of insulin for weight loss (or misreporting of insulin administration) and arrange appropriate psychological and nutritional counseling and support when indicated.

PROMOTING DIETARY ADHERENCE — Motivating a person to make a long-term commitment to dietary alterations is a challenge. While nutritional counseling by clinicians in the diabetes health care team is essential, ultimately individuals determine what they are willing or able to do to achieve improved glycemic control.

The dietary prescription should begin by determining the patient's dietary preferences, physical activity patterns, medication dosing and adherence, social support, education level, time, financial constraints, and other challenges, as well as the need and/or desire for weight management. A dietary history, along with several days of food records, is helpful in an assessment of caloric intake, dietary content, 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 toward a more ideal diet and eating pattern. It is important to remember that the more marked the changes are from what the patient likes to eat, the less likely that the patient will adhere with the dietary prescription [16]. The individual's own food records and motivation to learn can be helpful in guiding decisions for the type of eating pattern (low carbohydrate, low fat, Mediterranean) and meal planning approach; choices between a detailed exchange system, sample menus, or basic or more advanced carbohydrate counting approaches can be made on an individual basis based on an assessment of lifestyle and learning capabilities [53].

If possible, teaching is done in a setting where real food can be used, so that the patient can become familiar with household measures and can improve their ability to estimate the carbohydrate content of foods commonly eaten. This is often best accomplished in dietary workshops for small groups of people [54].

During follow-up visits, it is important for the clinician to ask specifically about diet and physical activity to reinforce their importance. Ideally, a patient should be able to quote their nutrition and exercise prescription in detail. People with type 1 diabetes, if possible, should specify how many grams of carbohydrate they aim to eat at each meal and snack during the day. Most adults should also be able to specify their insulin correction factor and carbohydrate-to-insulin ratios for meals. All people with type 1 diabetes should be well trained in methods to prevent and treat hypoglycemia.

Many 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) [55]. (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 [56]. 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) [55]. (See "Obesity in adults: Behavioral therapy", section on 'Setting behavioral goals'.)

Adults 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 [57].

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 [58,59].

Periodic adjustments are necessary in the patient's comprehensive plan for diet, exercise, stress, and pharmacologic interventions to achieve and maintain glycemic goals and prevent complications. The clinician needs to maintain awareness of the patient's changing lifestyle patterns and help the individual make adaptations in their plan accordingly.

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 1 diabetes (The Basics)" and "Patient education: Diabetes and diet (The Basics)" and "Patient education: Carb counting for adults with diabetes (The Basics)" and "Patient education: My child has diabetes: How will we manage? (The Basics)" and "Patient education: Controlling blood sugar in children with diabetes (The Basics)" and "Patient education: Carb counting for children with diabetes (The Basics)" and "Patient education: Managing diabetes in school (The Basics)")

Beyond the Basics topics (see "Patient education: Type 1 diabetes: Overview (Beyond the Basics)" and "Patient education: Type 1 diabetes and diet (Beyond the Basics)" and "Patient education: Blood glucose monitoring in diabetes (Beyond the Basics)" and "Patient education: Type 1 diabetes: Insulin treatment (Beyond the Basics)")


Medical nutrition therapy – Medical nutrition therapy (MNT) is the process by which the nutrition prescription is customized for each individual based on medical, lifestyle, and personal factors. It is an integral component of diabetes management and diabetes self-management education. Key aspects of MNT for people with type 1 diabetes include (see 'Medical nutrition therapy' above):

Personal dietary preferences

Consistency in day-to-day carbohydrate intake

Dosing insulin for variations in blood glucose, food, and activity

Weight management

Nutritional content

Meal-insulin timing

Meal planning and insulin dosing – Maintaining a consistent day-to-day carbohydrate intake at meals and snacks allows insulin adjustments to be made to usual carbohydrate intake. Learning to adjust insulin in response to hyperglycemia and variations in carbohydrate intake at meals allows for more flexibility; further adjusting insulin dosing for high-fat and high-protein meals is a more advanced skill. (See 'Carbohydrate consistency' above.)

Weight management – Modifying caloric intake, along with appropriate behavioral interventions, is important for the patient with type 1 diabetes who has overweight or obesity, or who has a high glycated hemoglobin (A1C) and glycosuria and is about to intensify diabetes management. An easy-to-use calorie calculator for roughly estimating caloric intake associated with weight maintenance uses the patient's age, sex, height, weight, and usual level of physical activity. To estimate caloric needs for weight loss of 1 to 2 pounds per week, subtract 500 to 1000 calories per day from weight maintenance calories. (See 'Estimating caloric intake for weight maintenance' 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 people with diabetes should be individualized, based upon weight loss goals, other comorbidities and 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. (See 'Nutritional content' above.)

Eating disorders – Eating disorders and insulin omission are common among young females with type 1 diabetes, manifested most commonly as bulimia and weight loss due to purposely missed or reduced insulin doses; poor glycemic control and increased retinopathy are consequences. (See 'Eating disorders' above.)

Dietary adherence – Promoting dietary adherence is a challenge. A registered dietitian can be helpful in developing and monitoring a nutrition prescription. Success can be fostered by tailoring the nutrition prescription to the individual's preferences, psychosocial condition, and lifestyle; reviewing food diaries; and providing positive feedback. (See 'Promoting dietary adherence' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges David McCulloch, MD, who contributed to earlier versions of this topic review.

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