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 their patients.

The nutrition prescription for patients with type 1 diabetes should aim to optimally manage the "ABCs" of diabetes control: glycated hemoglobin (A1C), blood pressure and low-density lipoprotein (LDL)-cholesterol. The prescription must also be tailored for the individual patient to address diabetes complications and other concomitant conditions. 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 risk factors and prevent complications of diabetes, both acute (hypoglycemia and short-term illness) and long-term (hypertension, hyperlipidemia, renal disease, cardiovascular disease, and other 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 individual patient characteristics.

The role of nutrition and the development of a medical nutrition therapy (MNT) plan for a patient with type 1 diabetes are discussed here. Nutrition for patients with type 2 diabetes, as well as insulin management for type 1 diabetes, is discussed separately. (See "Nutritional considerations in type 2 diabetes mellitus" and "Management of blood glucose in adults with type 1 diabetes mellitus".)

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

Randomized controlled trials of MNT have demonstrated decreases in A1C of up to 1.9 percentage points in three to six months in patients with type 1 diabetes [1,2]. In the Diabetes Control and Complications Trial (DCCT), specific diet behaviors were associated with achieving up to a 1 point lower mean A1C (8 versus 7 percent) in the intensive treatment group [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 control [2-5]. Glycemic control has been shown to markedly diminish the likelihood of neuropathy, nephropathy, retinopathy, and coronary artery disease in patients with type 1 diabetes [6,7]. (See "Glycemic control and vascular complications in type 1 diabetes mellitus".)

MNT for type 1 diabetes should consider five key aspects:

●Consistency in day-to-day carbohydrate intake

●Adjusting insulin for variations in blood glucose, food, or activity

●Weight management

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

●Meal-insulin timing

CARBOHYDRATE CONSISTENCY — Variations in food intake, particularly carbohydrate intake, can result in erratic blood glucose levels and hypoglycemia in patients with type 1 diabetes. Intensive insulin regimens, which combine a basal insulin with short-acting premeal insulins, do allow for some flexibility in the carbohydrate content of meals. In one study of patients receiving intensive insulin therapy, as an example, the total amount of carbohydrate in the meal did not influence glycemic response if premeal insulin was adjusted for variations in the carbohydrate content of the meal [8]. Patients who use short-acting insulin analogs or who use insulin pumps may need to take additional bolus insulin injections with snacks that contain more than 10 to 15 g of carbohydrate.

For patients receiving fixed doses of short- and intermediate-acting insulin, however, day-to-day consistency in the amount of carbohydrate and source of carbohydrate at meals and snacks is more important. Carbohydrate consistency for these patients has been associated with lower A1C levels, whereas day-to-day variations in calorie, protein, or fat intakes were not significantly related to A1C [9].

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 individual patients is determined by an assessment of their lifestyle and learning capabilities.

Basic carbohydrate counting — In its simplest form, the goal of carbohydrate counting is to promote glycemic control 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 glycemic control [10].

Patients who have been instructed in carbohydrate counting 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.

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 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 [11]. 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 [11].

The exchange system meal planning approach can be used as a tool to help patients achieve calorie, fat, and carbohydrate goals. However, many patients 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 patients 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 patients who have fairly routine eating habits and who do not eat a wide variety of foods. They also are appropriate for patients who need structured guidance on what to eat.

Insulin adjustments

Advanced carbohydrate counting — At a more advanced level, carbohydrate counting focuses on adjustment of food, insulin, and activity based on patterns from detailed logs. The patient needs to record time of meals and snacks, the amount and type of food eaten, amount of carbohydrate consumed, insulin dose, physical activity, and blood glucose results. Patients should first practice eating consistent amounts of carbohydrate at meals and snacks so that baseline insulin requirements can be matched to usual carbohydrate intake using pre- and postprandial blood glucose testing results. When pre- and postprandial blood 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 premeal 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.

Two other methods to calculate insulin-to-carbohydrate ratios are the 450 to 500 rule and the weight method [11]. These methods do not take into account individual variation and, therefore, are not as accurate as using detailed records.

●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 patient 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.

●Weight method – The weight method uses the data in the table (table 4) to calculate the insulin-to-carbohydrate ratio [11].

Elevated blood glucose levels — 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 patient 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 patient had a premeal blood glucose of 180 mg/dL and wanted to correct to a premeal blood glucose of 100 mg/dL, then the patient 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 — If the patient were hypoglycemic (blood glucose <70 mg/dL), then the patient would 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. 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. 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 glycemic control, weight control, reduction in comorbidities (hypertension, dyslipidemia, and cardiovascular disease), improved mood, and quality of life. The Institute of Medicine (now called the National Academy of Medicine) recommends that most adults engage in 30 minutes or more of moderate intensity physical activity on most days of the week [12]. Individuals for whom weight loss and weight maintenance are a concern may need more than this, and 60 to 90 minutes of moderate to vigorous intensity activity is encouraged. (See "Effects of exercise in adults with diabetes mellitus".)

Although exercise has not been consistently shown to improve glycemic control for patients with type 1 diabetes [13,14], patients who learn to self-adjust their diet or insulin to accommodate exercise can achieve near-normal A1C levels without undue hypoglycemia. For patients who are trying to lose weight, it is preferable to adjust insulin doses rather than increase food intake to compensate for exercise. Timing of exercise in relation to insulin dose, type, mode of delivery, and time of injection should be considered. Patients with diabetes should check blood glucose levels before and after exercising, especially in the beginning of an exercise program, to evaluate glycemic response to exercise and adjust insulin regimen. Patients should be advised to have a snack handy, in case blood glucose levels drop too low.

WEIGHT MANAGEMENT — The relative importance of caloric intake for an individual patient 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

●Genetics

●A1C

Lowering caloric intake and inducing weight loss are of major importance for overweight (body mass index [BMI] ≥25 to 29.9 kg/m²) and obese (BMI ≥30 kg/m²) patients with type 1 diabetes 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, glycemic variability, microvascular complications, and cardiovascular risk factors [1].

If patients have been close to ideal weight for several years and have a near normal A1C, then their current caloric intake is most likely appropriate.

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 and glycosuria is eliminated [15,16]. 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 [16]. At study end, 33 percent of the intensive therapy group was overweight compared with 19 percent of the conventional treatment group [17].

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 noncompliance with insulin therapy. As examples, approximately 30 percent of women with type 1 diabetes in one study occasionally omitted insulin injections intentionally [18]; in a second study, 9 percent did so on a regular basis in order to avoid weight gain [19]. (See 'Eating disorders' below.)

Estimating desirable body weight — Desirable body weight range can be roughly estimated by adding and subtracting 10 percent to the weights calculated as follows [20]:

●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)

BMI is now commonly used in research and clinical care as a classification of weight status and is calculated as: [weight in kg ÷ (height in m)²]. Optimal body weight is a BMI between 18.5 and 24.9 kg/m² (calculator 1).

Estimating caloric intake — 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 5) [21].

A rough estimate of caloric needs to maintain body weight can be determined as follows [22]:

●Men and active women – 15 kcal/lb

●Most women, sedentary men, and adults over 55 years – 13 kcal/lb

●Sedentary women and obese adults – 10 kcal/lb

●Pregnant, lactating women – 15 to 17 kcal/lb

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. 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.

NUTRITIONAL CONTENT — The optimal macronutrient composition of the diet for patients with diabetes is controversial [1]. The best mix of carbohydrate, protein, and fat may vary depending on the individual. American Diabetes Association (ADA) nutritional guidelines do not give specific total dietary compositional targets, except for the following recommendations [1,23]:

●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 (basic or advanced carbohydrate counting) 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. Sugar-sweetened beverages should be avoided in order to control glycemia, weight, and reduce risk for cardiovascular disease and fatty liver.

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

●Fat quality is more important than fat quantity. 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.

●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 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.

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 (CVD) mortality and therefore should be avoided [24].

●Fiber intake should be at least 14 grams per 1000 calories daily; higher fiber intake may improve glycemic control. 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 [25]. 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 also uncertain; these include protein, fiber (especially soluble), acid content of foods, particle size, food processing regimens, and rate and efficiency of digestion and absorption of different nutrients [26,27].

People with type 1 diabetes typically consume more saturated fat than is recommended. 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) [28].

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 [29,30]. 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 (table 6).

●Glycemic load is the product of the glycemic index value of a food and its total carbohydrate content [31,32]. 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, low glycemic index diets in individuals with diabetes or at risk for diabetes had equivocal impact on A1C compared with other diets, leading to uncertainty in its utility in clinical care [1,33,34]. 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 [1].

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 [1]. If patients choose to ingest alcohol, they should 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. Patients with type 1 diabetes should use blood glucose monitoring to assess any immediate or delayed effects of alcohol intake on blood glucose levels.

Dietary recommendations — In view of these observations, we recommend customizing dietary recommendations to the patients' abilities and lifestyle, with changes centered on managing total carbohydrate intake at meals and snacks, and use of whole grains in preference to refined grains and starches.

Carbohydrate counting is important for patients with type 1 diabetes who generally adjust their mealtime insulin based on carbohydrate content [23]. For patients with the ability to take additional steps to manage diabetes and prevent complications, learning to adjust insulin doses for variations in food intake or changes in activity will be beneficial.

It is also crucial to distinguish between types of fat in the diet, lowering saturated fat and avoiding hydrogenated fats, while consistently including monounsaturated and omega-3 fatty acids in the diet [1]. Protein intake should be appropriate to medical condition. In addition, patients with diabetes also need to assure that their diet is adequate in fiber content and essential vitamins and minerals. There is no clear evidence of benefit from vitamin and mineral supplementation in people with diabetes who do not have underlying deficiencies [25].

MEAL-INSULIN TIMING — Traditionally, consistent timing of food intake was an important aspect of nutrition in patients treated with insulin regimens to attain goals for glycemic control without undue hypoglycemia [2,10,35]. Meal timing at regular intervals is most important for patients receiving fixed doses of short- and intermediate-acting insulin. Newer rapidly-acting insulin preparations, however, allow for more flexibility in meal schedules and content.

Traditional insulin regimens were based on the injection of roughly the same amount of insulin at the same time each day. If the amount and timing of carbohydrate intake varied widely, blood glucose profiles fluctuated, with little chance of achieving target A1C values without a substantial risk of hypoglycemia. (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 for patients receiving intensive insulin therapy is to determine how much short- or rapid-acting insulin is needed to cover a certain amount of carbohydrate. Patients vary considerably in the amount of insulin required to cover a set amount of carbohydrate; some patients need a different carbohydrate-to-insulin ratio at different meals. Once the ratio is established, patients have flexibility to vary the amount of carbohydrate ingested at particular meals.

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 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.

A cautious approach to increasing insulin doses for high-fat and/or high-protein meals to address delayed hyperglycemia that may occur three hours after eating is recommended because blood glucose responses to mixed meals high in protein and/or fat along with carbohydrate have been found to differ among individuals. The effectiveness of such insulin dosing adjustments should be confirmed with individual self-monitoring of blood glucose (SMBG) or continuous glucose monitoring (CGM) results [1]. (See "Glucose monitoring in the management of nonpregnant adults with diabetes mellitus".)

EATING DISORDERS — Eating disorders are relatively common in patients with diabetes, especially in female adolescents and young adults with type 1 diabetes [36]. Eating disorders have a deleterious impact on glycemic control and on long-term outcome in these patients. One study evaluated 91 females with type 1 diabetes (mean age 15 years) at baseline and at follow-up four to five years later [37]. 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 or omission of insulin for weight loss and binge eating were the most common eating disorders.

●Disordered eating was associated with adverse outcomes [37,38]. 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). Patients with eating disorders were more likely to have retinopathy at follow-up.

It is important to evaluate patients with diabetes, especially young women, for an eating disorder (or misreporting of insulin administration) and arrange appropriate psychological and nutritional counseling and support when indicated.

PROMOTING DIETARY COMPLIANCE — Motivating a patient 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 patients 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 constraints, and other challenges. 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 the patient 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 [10]. The patient's own food records and motivation to learn can be helpful in guiding decisions for 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 [39].

A diet consistent in carbohydrate is desired in patients with type 1 diabetes interested in intensive insulin therapy. The patient about to begin intensive insulin therapy must be cautioned about the potential to gain weight, and the need for weight monitoring [16].

Achieving and maintaining weight reduction is difficult in any patient with obesity. Compliance can occasionally be enhanced by the rapid and often dramatic improvements in glycemic control.

Teaching is best done 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 carbohydrate content of foods commonly eaten. This is often best accomplished in dietary workshops for small groups of patients [40].

During follow-up visits, it is important for the clinician to ask specifically about diet and exercise to reinforce their importance. Ideally, a patient should be able to quote his or her nutrition and exercise prescription in detail. Patients with type 1 diabetes 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. Most patients should also be able to specify their insulin correction factor and carbohydrate-to-insulin ratios for meals. Patients should be well trained in methods to treat hypoglycemia to prevent overcompensation.

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) [41]. (See "Effects of exercise 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 [42]. 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) [41]. (See "Obesity in adults: Behavioral therapy", section on 'Setting behavioral goals'.)

●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 [43].

●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 [44,45].

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 clinician needs to maintain awareness of the patient's changing lifestyle patterns and help the patient 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 5^th to 6^th 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 10^th to 12^th 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: Counting carbs if you do not use insulin (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)")

SUMMARY AND RECOMMENDATIONS

●The five key aspects of the nutritional management of type 1 diabetes are (see 'Medical nutrition therapy' above):

•Consistency in day-to-day carbohydrate intake

•Adjusting insulin for variations in blood glucose, food, or activity

•Weight management

•Nutritional content

•Meal-insulin timing

●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 is a more advanced skill. (See 'Carbohydrate consistency' above.)

●Modifying caloric intake, along with appropriate behavioral interventions, is important for the patient with type 1 diabetes who is overweight, or who has a high glycated hemoglobin (A1C) and glycosuria and is about to intensify diabetes management. Approximate caloric intake and estimates of desirable body weight can be made by formulas presented above. (See 'Estimating caloric intake' above and 'Estimating desirable body weight' above.)

●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. (See 'Nutritional content' above.)

●Eating disorders are common among young female patients 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.)

●Promoting dietary compliance is a challenge, and a registered dietitian can be helpful in developing and monitoring a nutrition prescription. Compliance can be fostered by tailoring the nutrition prescription to the individual patient's preferences and lifestyle, reviewing food diaries, and providing positive feedback with improved glycemic control. (See 'Promoting dietary compliance' above.)

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