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Diabetes Nutrition Therapy: Effectiveness, Macronutrients, Eating Patterns and Weight Management

Published:February 24, 2016DOI:https://doi.org/10.1016/j.amjms.2016.02.001

      Abstract

      Background

      Diabetes nutrition therapy provided for individuals with diabetes must be based on research documenting effectiveness. The roles of differing macronutrient percentages, eating patterns and weight loss interventions are controversial.

      Methods

      A review of research related to these topics is summarized.

      Results

      Clinical trials as well as systematic reviews and Cochrane reviews report an approximately 1-2% lowering of hemoglobin A1c as well as other beneficial outcomes from nutrition therapy interventions, depending on the type and duration of diabetes and level of glycemic control. There are no ideal percentages of macronutrients or eating patterns or both that apply to all persons with diabetes. Clinical trials demonstrate the effectiveness of modest weight loss and physical activity for the prevention or delay of type 2 diabetes. However, as the disease progresses, weight loss interventions may or may not result in beneficial glycemic and other metabolic outcomes.

      Conclusions

      To be effective, diabetes nutrition therapy must be individualized. Treatment goals, personal preferences (eg, tradition, culture, religion, health beliefs and economics) and the individual׳s ability and willingness to make lifestyle changes all must be considered when educating or counseling individuals with diabetes. A healthy eating pattern emphasizing nutrient-dense foods in appropriate portion sizes, regular physical activity and support are important. A reduced energy intake for persons with prediabetes or type 2 diabetes and matching insulin to planned carbohydrate intake for insulin users is nutrition therapy interventions shown to be effective in achieving glycemic and other metabolic outcomes.

      Key Indexing Terms

      Introduction

      As research provides evidence for the role of nutrition therapy in diabetes management, it is important that traditional nutrition therapy advice given to individuals with diabetes be updated to reflect the latest evidence. The goal of diabetes nutrition therapy is to implement interventions that promote healthy eating and assist in achieving glucose, lipid and blood pressure goals.
      • Franz M.J.
      • Powers M.A.
      • Leontos C.
      • et al.
      The evidence for medical nutrition therapy for type 1 and type 2 diabetes in adults.
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      The first question, and perhaps the most important, is: what is the evidence that diabetes nutrition therapy is effective, and if effective, what nutrition therapy interventions result in positive metabolic outcomes. Second, are there ideal percentages of macronutrients and eating patterns that should be recommended to persons with diabetes? Third, what is the role of weight loss interventions (WLIs) across the continuum of diabetes management, from prevention to management of diabetes?
      Medical recommendations, including those for nutrition therapy, are now being developed using an evidence-based approach. The Academy of Nutrition and Dietetics is currently updating their evidence-based nutrition recommendations for type 1 and type 2 diabetes published in 2010
      • Franz M.J.
      • Powers M.A.
      • Leontos C.
      • et al.
      The evidence for medical nutrition therapy for type 1 and type 2 diabetes in adults.
      and The American Diabetes Association (ADA) in 2013 published nutrition therapy recommendations for management of adults with diabetes using a similar process.
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      Both are the basis for the recommendations cited in this article. This article (1) reviews effectiveness and outcomes of diabetes nutrition therapy and nutrition therapy interventions that are effective, (2) examines evidence that supports recommendations for diabetes-related macronutrient intake and eating patterns and (3) reviews the role of WLIs in the management of type 2 diabetes.

      Effectiveness of Diabetes Nutrition Therapy

      Multiple studies provide evidence that across the diabetes continuum, diabetes nutrition therapy is effective for improving glycemic control and other metabolic outcomes. Of importance are the clinical trials that document the effectiveness of nutrition therapy for the prevention or delay of type 2 diabetes. Lifestyle interventions—an eating plan that facilitates moderate weight loss (5-7% of body weight) and increased physical activity (equivalent to 30 minutes brisk walking on most days of the week)—follow-up counseling and continued support initially decreased risk of diabetes by 58%. During a mean follow-up of 15 years, diabetes incidence in the lifestyle group continued to be reduced by 27% and in the metformin group by 18% compared with the placebo group, supporting the importance of lifestyle interventions in diabetes prevention.
      • Diabetes Prevention Program Research Group
      Long-term effects of lifestyle intervention or metformin on diabetes development and microvascular complications over 15-year follow-up of the Diabetes Prevention Program Outcomes Study.
      Nutrition therapy interventions implemented by registered dietitian nutritionists are reported to lower hemoglobin A1c (A1C) levels by an average of 1-2% (range: 0.23-2.6%) depending on the type and duration of diabetes and the A1C level at implementation.
      • Franz M.J.
      • Powers M.A.
      • Leontos C.
      • et al.
      The evidence for medical nutrition therapy for type 1 and type 2 diabetes in adults.
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      • Pastors J.G.
      • Franz M.J.
      Effectiveness of medical nutrition therapy in diabetes.
      For example, implementation of nutrition therapy in persons with newly diagnosed type 2 diabetes and an A1C of approximately 9% resulted in a decrease of approximately 2%, whereas in persons newly diagnosed with an A1C levels of approximately 6.6% the decrease was 0.4%, both decreases were significant and clinically meaningful.
      • Pastors J.G.
      • Franz M.J.
      Effectiveness of medical nutrition therapy in diabetes.
      Even in persons with a long duration of type 2 diabetes (approximately 9 years) not optimally controlled, implementation of nutrition therapy decreased A1C by approximately 0.5%, which was significant and more cost-effective than adding a third medication.
      • Pastors J.G.
      • Franz M.J.
      Effectiveness of medical nutrition therapy in diabetes.
      In persons with type 1 diabetes, implementation of nutrition therapy based on adjustments in insulin to cover carbohydrate intake improved A1C by approximately 1% and improved quality of life without worsening of hypoglycemia or cardiovascular risk.
      • DAFNE Study Group
      Training in flexible, intensive insulin management to enable dietary freedom in people with type 1 diabetes: dose adjusted for normal eating (DAFNE) randomised controlled trial.
      Furthermore, the outcomes of nutrition therapy are known by 6 weeks to 3 months; at this time it can be determined if therapy goals have been reached or if medications need to be combined with nutrition therapy. Studies in persons with type 1 or type 2 diabetes have reported similar beneficial glycemic results that are maintained and other beneficial outcomes, including improved lipid profiles, weight loss, decreased blood pressure, decreases in medications and decreased risk of onset and progression to diabetes-related comorbidities.
      • Pastors J.G.
      • Franz M.J.
      Effectiveness of medical nutrition therapy in diabetes.
      Of interest are the types of nutrition therapy interventions implemented, that is, reduced energy or fat intake, carbohydrate counting, simplified eating plans or healthy food choices, use of insulin-to-carbohydrate ratios, physical activity and behavioral strategies.
      • Pastors J.G.
      • Franz M.J.
      Effectiveness of medical nutrition therapy in diabetes.
      A unifying focus of nutrition therapy interventions for type 2 diabetes is a reduced energy intake and for type 1 diabetes, adjusting insulin to cover planned carbohydrate intake.
      • Pastors J.G.
      • Franz M.J.
      Effectiveness of medical nutrition therapy in diabetes.
      It is essential that the person with diabetes be actively involved with health professionals to collaboratively develop an eating plan that they can implement. Multiple encounters to provide education and counseling initially and on a continued basis are also essential.
      • Pastors J.G.
      • Franz M.J.
      Effectiveness of medical nutrition therapy in diabetes.

      Macronutrients and Eating Patterns

      In the United States, most adults and youth with type 1 or type 2 diabetes report eating moderate amounts of carbohydrate (approximately 46-48% of total energy intake) and approximately 35-40% of energy intake from fat with the remainder from protein.
      • Oza-Frank R.
      • Cheng Y.J.
      • Narayan K.M.
      • et al.
      Trends in nutrient intake among adults with diabetes in the United States: 1988-2004.
      • Mayer-Davis E.J.
      • Nichols M.
      • Liese A.D.
      • et al.
      Dietary intake among youth with diabetes: the SEARCH for Diabetes in Youth Study.
      The ADA׳s review of evidence concluded that there is no most effective mix of carbohydrate, protein and fat that applies broadly; macronutrient proportions should be individualized and adjusted to meet metabolic goals and preferences of the person with diabetes.
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      What emerges from the evidence is the importance of total energy intake rather than the source of the energy.
      Because all the 3 macronutrients require insulin for metabolism and influence the attaining of goals of nutrition therapy, including healthy eating, they still must be addressed. The amount rather than the type of carbohydrate and available insulin is the primary determinant of postprandial glycemia.
      • Rabasa-Lhoret R.
      • Garon J.
      • Langelier H.
      • et al.
      Effects of meal carbohydrate content on insulin requirements in type 1 diabetic patients treated intensively with basal-bolus (ultralente-regular) insulin regimen.
      Therefore, monitoring carbohydrate intake, whether by carbohydrate counting or experience-based estimation, remains a key strategy in achieving glycemic control.
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      Carbohydrate counting focuses on total amount of carbohydrate in foods and not the source (15 g carbohydrate = 1 carbohydrate choice). An eating plan for adult women often begins with 3-4 carbohydrate choices per meal and for adult men 4-5 carbohydrate choices. Collaboration with the patient is then used to determine if this is an eating plan that can be followed for long term or if changes need to be made to the eating plan can so it can be followed for long term.

      Macronutrients and Insulin Adjustments

      Carbohydrate is the main macronutrient influencing postprandial glycemia.
      • Rabasa-Lhoret R.
      • Garon J.
      • Langelier H.
      • et al.
      Effects of meal carbohydrate content on insulin requirements in type 1 diabetic patients treated intensively with basal-bolus (ultralente-regular) insulin regimen.
      Therefore, for individuals taking insulin by injection or by insulin pumps, the bolus or mealtime insulin dose covers the need of carbohydrate for insulin and is approximately half of the total insulin dose. If the bolus dose covers carbohydrate, it is assumed that the basal or background insulin dose covers the need for usual intake of protein and fat for insulin.
      • Smart C.E.M.
      • Evans M.
      • O׳Connell S.M.
      • et al.
      Both dietary protein and fat increase postprandial glucose concentrations in children with type 1 diabetes, and the effect is additive.
      Basal or background insulin also facilitates the uptake of glucose between meals and overnight.
      Insulin-to-carbohydrate ratios are used to match bolus doses of rapid-acting insulin taken before a meal to planned carbohydrate intake, which is determined by carbohydrate counting. However, a study done in young people using intensive insulin therapy reported that small inaccuracies in carbohydrate intake at a meal (±10 g) does not increase risk of hypoglycemia or hyperglycemia and therefore it is not essential to count carbohydrate in grams, carbohydrate servings (choices) can be used.
      • Smart C.E.
      • Ross K.
      • Edge J.A.
      • et al.
      Children and adolescents on intensive insulin therapy maintain postprandial glycemic control without precise carbohydrate counting.
      If the premeal glucose level is not in target goal range, rapid-acting insulin doses need to be added or subtracted from the usual bolus insulin dose. This is called the blood glucose correction insulin, also known as the insulin sensitivity factor, and is used to bring blood glucose levels back into target range. If blood glucose levels are high before a meal, additional rapid-acting insulin is added to the mealtime dose. If blood glucose levels are low before a meal, subtraction of rapid-acting insulin from the mealtime dose is recommended. The Table illustrates commonly used insulin-to-carbohydrate ratios and blood glucose correction insulin doses (insulin sensitivity factors).
      American Diabetes Association, Academy of Nutrition and Dietetics. Match Your Insulin to Your Carbs. American Diabetes Association, Alexandria, VA, Academy of Nutrition and Dietetics, Chicago, IL; 2014.
      TABLEGeneral guidelines for insulin-to-carbohydrate ratios and blood glucose correction insulin factors. Insulin-to-carbohydrate ratios are 1 unit of rapid-acting insulin for grams of planned carbohydrate intake. The blood glucose correction insulin is the approximate glucose lowering in mg/dL from an added 1 unit of rapid-acting insulin. The insulin dose is taken before the meal.
      Insulin-to-carbohydrate ratioBlood glucose correction insulin
      Adult (normal weight)1:10-1:151:40-1:50
      Adult (overweight)1:7-1:101:30-1:40
      Adult (obese)1:51:25
      Source: American Diabetes Association, Academy of Nutrition and Dietetics. Match Your Insulin to Your Carbs.
      American Diabetes Association, Academy of Nutrition and Dietetics. Match Your Insulin to Your Carbs. American Diabetes Association, Alexandria, VA, Academy of Nutrition and Dietetics, Chicago, IL; 2014.
      As noted, usually consumed meals contain moderate amounts of protein and fat and this is already accounted for by usual basal and bolus insulin doses.
      • Paterson M.A.
      • Smart C.E.M.
      • Lopez P.E.
      • et al.
      Influence of dietary protein on postprandial blood glucose levels in individuals with type 1 diabetes mellitus using intensive insulin therapy.
      • Peters A.L.
      • Davidson M.B.
      Protein and fat effects on glucose responses and insulin requirements in subjects with insulin-dependent diabetes mellitus.
      However, research using excessively high intakes of protein or fat has documented the need for additional insulin.
      • Paterson M.A.
      • Smart C.E.M.
      • Lopez P.E.
      • et al.
      Influence of dietary protein on postprandial blood glucose levels in individuals with type 1 diabetes mellitus using intensive insulin therapy.
      • Wolpert H.A.
      • Atakov-Castillo Smith
      • Sa
      • et al.
      Dietary fat acutely increases glucose concentrations and insulin requirements in patients with type 1 diabetes: implications for carbohydrate-based bolus dose calculation and intensive diabetes management.
      A study in young people concluded that only large meals containing 75 and 100 g protein raised glucose levels in the late postprandial (180-130 minutes) when compared with control.
      • Smart C.E.M.
      • Evans M.
      • O׳Connell S.M.
      • et al.
      Both dietary protein and fat increase postprandial glucose concentrations in children with type 1 diabetes, and the effect is additive.
      Meals containing 12.5, 25 and 50 g protein did not significantly increase glucose levels. The effect of larger amounts of protein and fat is additive; however, responses vary greatly and research at this time does not provide guidelines for insulin adjustments.

      Carbohydrate Intake

      A total of 2 observational studies reported that a moderately higher carbohydrate intake compared to a lower carbohydrate was associated with better glycemic control.
      • Delahanty L.M.
      • Nathan D.M.
      • Lachin J.M.
      • et al.
      Association of diet with glycated hemoglobin during intensive treatment of type 1 diabetes in the Diabetes Control and Complications Trial.
      • Xi J.
      • Eilat-Adar S.
      • Loria C.M.
      • et al.
      Macronutrient intake and glycemic control in a population-based sample of American Indians with diabetes: the Strong Heart Study.
      Dietary intakes from 532 of the intensively treated Diabetes Control and Complications Trial participants through 5 years of Diabetes Control and Complications Trial follow-up reported a mean higher carbohydrate of 56% of total energy intake associated with a significantly lower A1C level of 7.1% compared to a mean lower carbohydrate intake of 37% associated with a higher A1C level of 7.5%, independent of exercise and body mass index.
      • Delahanty L.M.
      • Nathan D.M.
      • Lachin J.M.
      • et al.
      Association of diet with glycated hemoglobin during intensive treatment of type 1 diabetes in the Diabetes Control and Complications Trial.
      In the Strong Health Study (n = 1,284 subjects with type 2 diabetes) intakes lower in carbohydrate (46%) and higher in total fat (37%) and saturated fat were associated with worse glycemic control (A1C ≥ 7% versus <7%) compared to higher carbohydrate (50%) and lower total fat (34%) intake.
      • Xi J.
      • Eilat-Adar S.
      • Loria C.M.
      • et al.
      Macronutrient intake and glycemic control in a population-based sample of American Indians with diabetes: the Strong Heart Study.
      Although intuitively it may seem that a lower carbohydrate intake would be beneficial, epidemiologic data and clinical trials have reported that long-term higher total fat intakes, especially saturated fats, results in greater whole-body insulin resistance.

      Estadella D, da Penha Oller do Nascimento CM, Oyama LM, et al. Lipotoxicity: effects of dietary saturated and trans fatty acids. http://doi.org/10.1155/2013/137579.

      • Lee J.S.
      • Pinnamaneni S.K.
      • Eo S.J.
      • et al.
      Saturated, but not n-6 polyunsaturated fatty acids induce insulin resistance: role of intramuscular accumulation of lipid metabolites.
      Although not as well studied in persons with diabetes, reducing saturated fat has been shown to improve insulin sensitivity.
      • Rosenfalck A.M.
      • Almdal T.
      • Viggers L.
      • et al.
      A low-fat diet improves peripheral insulin sensitivity in patients with type 1 diabetes.
      The influence of long-term intake of saturated fatty acids on insulin resistance is of importance because as people with diabetes lower their intake of carbohydrate, they increase their fat intake, especially saturated fat. (It is difficult to change protein intake for long term.)
      For good health, carbohydrate intake from vegetables, fruits, whole grains, legumes and low-fat dairy products are recommended to be advised over intake from other carbohydrate sources especially those that contain added fats, sugars and sodium.
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      Of importance are appropriate amounts and portions sizes of carbohydrate foods. However, negotiating with individuals with diabetes as to what they are willing and able to do is essential.

      Glycemic Index

      The types of carbohydrate, especially the role of the glycemic index (GI) have been another area of controversy and the definition of the GI is confusing. The GI measures the relative area under the postprandial glucose curve comparing 50 g of a digestible carbohydrate from a test food to 50 g glucose.
      • Brand-Miller J.C.
      • Stockmann K.
      • Atkinson F.
      • et al.
      Glycemic index, postprandial glycemia, and the shape of the curve in healthy subjects: analysis of a database of more than 1000 foods.
      It does not measure how rapidly blood glucose levels increase after eating different carbohydrate foods, which is the definition often given to the public. The second definition implies that a high-GI food produces a rapid, high glucose peak, whereas a low-GI food produces a more gradual and sustained glucose response. A review by Brand-Miller et al
      • Brand-Miller J.C.
      • Stockmann K.
      • Atkinson F.
      • et al.
      Glycemic index, postprandial glycemia, and the shape of the curve in healthy subjects: analysis of a database of more than 1000 foods.
      compared the glucose curve from different types (eg, breads, cereals, potatoes, pasta, fruit and fruit juice) of low-GI and high-GI foods in persons without diabetes. They reported no statistical difference in the glucose response curve from different foods. Glucose peaks occurred consistently at approximately 30 min, regardless of whether the food was categorized a low-GI, medium-GI or high-GI, with a modest difference in glucose peak values between high-GI and low-GI foods. The authors concluded that low-GI foods do not produce a slower rise in blood glucose nor do they produce an extended, sustained glucose response.
      The ADA systematic review of macronutrients concluded that, in general, there is little difference in glycemic control and cardiovascular death risk factors between low-GI and high-GI or other diets. A slight improvement in glycemia may result from lower-GI diets; however, confounding by a higher fiber intake is not accounted for.
      • Wheeler M.L.
      • Dunbar S.A.
      • Jaacks L.M.
      • et al.
      Macronutrients, food groups and eating patterns in the management of diabetes: a systematic review of the literature. 2010.
      As with carbohydrates, most individuals with diabetes likely consume a moderate-GI diet, and it is unknown if reducing the usual GI by a few percentage points would result in long-term improved glycemic control.

      Protein

      Gram for gram protein is reported to require similar amounts of insulin for metabolism as do carbohydrates.
      • Papakonstantinou E.
      • Triantafilidou D.
      • Banagiotakos D.B.
      • et al.
      A high protein low fat meal does not influence glucose and insulin responses in obese individuals with or without type 2 diabetes.
      Although essential amino acids undergo gluconeogenesis in the liver, the glucose does not enter the general circulation but instead is stored as glycogen. Adding protein to bedtime snacks is often recommended to prevent overnight hypoglycemia or to be added to the treatment of hypoglycemia, but adding protein to prevent hypoglycemia is not beneficial (because as noted earlier, the glucose from gluceoneogenesis does not enter the general circulation) and therefore should not be recommended to all persons with diabetes for the prevention of hypoglycemia.
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      Also of interest is the role of protein restriction in the treatment of diabetic kidney disease. Although reducing protein intake below usual intake in individuals with microalbuminuria or macroalbuminuria may reduce albuminuria, it does not alter the glomerular filtration rate decline and is not recommended.
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.

      Can Macronutrient Intake Be Changed for Long Term?

      Although research studies may show benefit from a variety of nutrition therapy interventions, including changes in macronutrient distribution, the important question remains: can individuals with diabetes implement these recommendations into their lifestyle for long term? Research studies are often of a relatively short duration and support from health professionals is provided during the study. Of interest are comments from researchers who have conducted a minimum of 1-year clinical trials involving changes in macronutrient distribution. Iqbal et al
      • Iqbal N.
      • Vetter M.L.
      • Moore R.H.
      • et al.
      Effects of a low-intensity intervention that prescribed a low-carbohydrate vs a low-fat diet in obese, diabetic participants.
      conducted a 24-month study to determine if benefits identified from short-term, intensive low-carbohydrate studies could be achieved using a low-intensity intervention that mimics what is feasible in an outpatient practice. A low-carbohydrate diet (<30 g/day) was compared to a low-fat diet (<30% of total kcal) with 54% completers in the low-fat arm and 40% completers in the low-carbohydrate arm. The low-carbohydrate diet did not produce any clinically significant changes in weight, A1C or lipids at any time point. Of interest, at 6 months the low-carbohydrate groups had decreased carbohydrate intake by 4.7% (35% of kcal) but at 12 months they were back to their baseline intake (40% of kcal) and at 24 months they had increased carbohydrate intake (48% of kcal). The authors concluded that low-carbohydrate diets may be difficult to sustain and that participants in the 2 groups appeared to consume similar diets, despite the prescription of markedly different intake.
      A total of 2 researchers compared a high protein intake (30% of kcal) to either a high-carbohydrate diet
      • Krebs J.D.
      • Elley C.R.
      • Parry-Strong A.
      • et al.
      The Diabetes Excess Weight Loss (DEWL) Trial: a randomized controlled trial of high-protein versus high-carbohydrate diets over 2 years in type 2 diabetes.
      or low-carbohydrate diet.
      • Larsen R.N.
      • Mann N.J.
      • Maclean E.
      • et al.
      The effect of high-protein, low-carbohdrate diets in the treatment of type 2 diabetes: a 12 month randomized controlled trial.
      Krebs et al
      • Krebs J.D.
      • Elley C.R.
      • Parry-Strong A.
      • et al.
      The Diabetes Excess Weight Loss (DEWL) Trial: a randomized controlled trial of high-protein versus high-carbohydrate diets over 2 years in type 2 diabetes.
      reported that the prescribed protein of 30% was achieved in only 12 of 207 (6%) of participants and noted that this “highlights how difficult it is to achieve and maintain prescribed change … individuals trend back to habitual intake over time. Larson et al
      • Larsen R.N.
      • Mann N.J.
      • Maclean E.
      • et al.
      The effect of high-protein, low-carbohdrate diets in the treatment of type 2 diabetes: a 12 month randomized controlled trial.
      commented: “under real-word conditions, variations in food selection and adherences are likely to attenuate the effect previously demonstrated in controlled feeding studies. All the 3 studies provide support for conclusion that “how much” individuals eat is more important than “what.”

      Eating Patterns

      The ADA nutrition recommendations also reviewed eating patterns (Mediterranean Style, vegetarian or vegan, low fat, low carbohydrate and Dietary Approaches to Stop Hypertension) and concluded that a variety of eating patterns (combinations of different foods or food groups) are acceptable for the management of diabetes.
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      When recommending one eating pattern over another eating pattern what is of importance is the individual׳s personal preferences (eg, tradition, culture, religion, health beliefs, goals and economic condition), metabolic goals and the individual׳s ability and willingness to make changes.

      The Role of WLIs in the Management of Diabetes

      Overweight and obesity are common health problems in persons at risk for and with type 2 diabetes and weight loss is frequently recommended as the solution to improve glycemic control.
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      In persons with prediabetes, modest amounts of weight loss and regular physical activity are effective in preventing or delaying the onset of type 2 diabetes.
      • Youssef G.
      Nutrition therapy and prediabetes.
      In individuals who have maintained lifestyle strategies for prevention of diabetes, the effectiveness of these strategies has been maintained for 15 years and longer.
      • Diabetes Prevention Program Research Group
      Long-term effects of lifestyle intervention or metformin on diabetes development and microvascular complications over 15-year follow-up of the Diabetes Prevention Program Outcomes Study.
      The WLIs have also been shown to be effective in improving glycemic control in individuals with newly diagnosed diabetes.
      • Feldstein A.C.
      • Nichols G.A.
      • Smith D.H.
      • et al.
      Weight change in diabetes and glycemic and blood pressure control.
      • Esposito K.
      • Maiorino M.I.
      • Ciotola M.
      • et al.
      Effects of a Mediterranean-style diet on the need for hyperglycemic drug therapy in patients with newly diagnosed type 2 diabetes: a randomized trial.
      The benefit of WLIs in type 2 diabetes of longer duration is controversial. To better understand the results of WLI, a systematic review and meta-analysis was conducted to answer the questions: in overweight and obese adults with type 2 diabetes, what are the outcomes on A1C, lipids and blood pressure from WLIs resulting in weight losses greater than or less than 5% at 12 months, and what are the weight and metabolic outcomes from differing amounts of macronutrients in WLI?
      • Franz M.J.
      • Boucher J.L.
      • Rutten-Ramos S.
      • et al.
      Lifestyle weight-loss intervention outcomes in overweight and obese adults with type 2 diabetes. a systematic review and meat-analysis of randomized clinical trials.
      A total of 11 trials (8 compared 2 WLI and 3 compared a WLI to a usual care or control group) with 6,754 participants met study criteria. At 12 months, 17 WLI arms reported weight losses less than 5% (1.9-4.8 kg) and nonsignificant benefits on A1C, lipids or blood pressure. Only 2 WLI study arms, a Mediterranean style in newly diagnosed adults and the intensive lifestyle intervention in the Look AHEAD trial resulted in weight loss greater than 5%. Both included regular physical activity and frequent contacts with health professionals and reported significant benefits on A1C, lipids and blood pressure. In all, 5 trials (10 study arms) compared WLI of differing amounts of macronutrients and reported nonsignificant differences in weight loss, A1C, lipids or blood pressure. Thus, a weight loss >5% (approximately 6 kg) appears necessary for beneficial metabolic outcomes. Achieving this level of weight loss requires intense interventions, including energy restriction, regular physical activity and frequent contact with health professionals.
      Furthermore, it appears difficult for persons with diabetes to lose weight. In a systematic review of 80 weight loss studies with 26,455 participants, primarily without diabetes, the average weight loss was 8% (7.5 kg) from baseline (compared to <5% in most studies in participants with type 2 diabetes).
      • Franz M.J.
      • VanWormer J.J.
      • Crain A.L.
      • et al.
      Weight loss outcomes: a systematic review and meta-analysis of weight-loss clinical trials with a minimum of 1-year duration.
      As noted, weight loss to improve glycemic control may be most beneficial for persons with diabetes early in the disease process. Factors that contribute to an individual׳s inability to loss and maintain weight loss include low socioeconomic status, an unsupportive environment and, very importantly, physiological changes (eg, compensatory changes after weight loss in circulating hormones that encourage weight regain and adaptive thermogenesis).
      • Warshaw H.S.
      Nutrition therapy for adults with type 2 diabetes.
      • Korner J.
      • Leibel R.L.
      To eat or not to eat—how the gut talks to the brain.
      • Major G.C.
      • Doucet E.
      • Trayhurn P.
      • et al.
      Clinical significance of adaptive thermogenesis.
      • Sumithran P.
      • Prednergast L.A.
      • Delbridge E.
      • et al.
      Long-term persistence of hormonal adaptations to weight loss.
      Therefore, the emphasis of nutrition therapy for individuals with type 2 diabetes should be on a reduced energy intake for improved glycemic control, regular physical activity and support for lifestyle changes, not the scale (in some it may lead to weight loss, in some it may maintain weight loss and in some it may prevent weight gain), regular physical activity and support for lifestyle changes.

      Conclusions

      Based on the evidence reviewed, the question becomes—what is the best nutrition therapy for diabetes? In an “ideal world,” the evidence suggests that all persons with type 2 diabetes would lose 5-10% of their baseline weight, have a nutrient-dense eating pattern in appropriate portion sizes and participate in 150 min per week of regular physical activity. All persons with type 1 diabetes would count carbohydrates, adjust premeal insulin based on insulin-to-carbohydrate ratios and use insulin correction factors. However, it is highly doubtful that this “ideal world” of diabetes management exists. Therefore, in the “real world” of diabetes management, it becomes important for health professionals to individualized nutrition-related strategies proven to be beneficial and to facilitate behavior changes that individuals are willing and able to make. Evidence has shown that a variety of nutrition therapy and physical activity interventions can be implemented and, very importantly, that nutrition therapy for diabetes is effective!

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