Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy
Dove Press
Evidence-based diabetes nutrition therapy recommendations are effective: the key is individualization
Marion J Franz, Jackie L Boucher, and Alison B Evert
Additional article information
Abstract
Current nutrition therapy recommendations for the prevention and treatment of diabetes are based on a systematic review of evidence and answer important nutrition care questions. First, is diabetes nutrition therapy effective? Clinical trials as well as systematic and Cochrane reviews report a ~1%–2% lowering of hemoglobin A1c values as well as other beneficial outcomes from nutrition therapy interventions, depending on the type and duration of diabetes and level of glycemic control. Clinical trials also provide evidence for the effectiveness of nutrition therapy in the prevention of diabetes. Second, are weight loss interventions important and when are they beneficial? Modest weight loss is important for the prevention of type 2 diabetes and early in the disease process. However, as diabetes progresses, weight loss may or may not result in beneficial glycemic and cardiovascular outcomes. Third, are there ideal percentages of macronutrients and eating patterns that apply to all persons with diabetes? There is no ideal percentage of macronutrients and a variety of eating patterns has been shown to be effective for persons with diabetes. Treatment goals, personal preferences (eg, tradition, culture, religion, health beliefs, economics), and the individual’s ability and willingness to make lifestyle changes must all be considered by clinicians and/or educators when counseling and educating individuals with diabetes. A healthy eating pattern emphasizing nutrient-dense foods in appropriate portion sizes, regular physical activity, and support are priorities for all individuals with diabetes. Reduced energy intake for persons with prediabetes or type 2 diabetes as well as matching insulin to planned carbohydrate intake are intervention to be considered. Fourth, is the question of how to implement nutrition therapy interventions in clinical practice. This requires nutrition care strategies.
Keywords: diabetes nutrition therapy, macronutrients, eating patterns, weight loss interventions
Introduction
The nutrition therapy recommended for people with diabetes is often based on theories or the opinions of the medical treatment provider. People with diabetes often find this frustrating or confusing, because they hear or read that ideally they should be on a low-carbohydrate diet but from other sources they are told that they should be eating a high-carbohydrate, high-protein, or low-fat diet. However, in recent years, there has been a shift in how medical recommendations for prevention and treatment of various diseases are developed. Medical recommendations, including those for nutrition therapy, are now being developed using an evidence-based approach. The Academy of Nutrition and Dietetics published evidence-based nutrition recommendations for type 1 and type 2 diabetes in 20101,2 and the American Diabetes Association (ADA) in 2013 published nutrition therapy recommendations for the management of adults with diabetes using a similar process.3 The ADA 2013 nutrition therapy recommendations are the basis for the majority of the recommendations cited in this review.
The goals of diabetes nutrition therapy are nutrition interventions that promote healthy eating and assist in achieving glucose, lipid, and blood pressure goals.1–3 The present paper reviews the updated diabetes nutrition therapy recommendations and several of the questions asked that determine the recommendations for achievement of the diabetes nutrition therapy goals in clinical practice. The first question, and perhaps the most important, is what is the evidence that nutrition therapy for persons with diabetes is effective, and if effective, what nutrition interventions result in positive health outcomes? An important second question is what is the role of weight loss interventions across the continuum of diabetes, from prevention of the disease to its management? Third, are there ideal percentages of macronutrients or eating patterns that should be recommended to persons with diabetes? Fourth, how can health professionals individualize and implement these recommendations when providing nutrition care for patients with diabetes?
Effectiveness of nutrition therapy
Multiple studies provide evidence that diabetes nutrition therapy is effective for improving glycemic control and other metabolic outcomes. Because it reflects average glycemia over several months, hemoglobin A1c (HbA1c) is used to assess glycemic control. Nutrition therapy interventions implemented by registered dietitians/nutritionists reduced HbA1c levels by an average of 1% to 2% (range −0.23% to −2.6%) depending on the type and duration of diabetes and the HbA1c level at implementation.1–4 For example, implementation of nutrition therapy in patients with newly diagnosed type 2 diabetes and an HbA1c of ~9% resulted in a decrease of ~2%,5 whereas persons newly diagnosed with HbA1c levels of ~6.6% experienced a decrease of 0.4%,6 both of which are significant and clinically meaningful. Even in patients with a long duration of type 2 diabetes of ~9 years and diabetes that was not optimally controlled, implementation of nutrition therapy decreased HbA1c by ~0.5%, which was significant and more cost-effective than adding a third medication.7 In persons with type 1 diabetes, implementation of nutrition therapy based on adjustments in insulin to cover carbohydrate intake improved HbA1c by ~1% and improved quality of life without worsening of hypoglycemia or cardiovascular risk.8 Other studies in subjects 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, decreased need for medication, and decreased risk of onset and progression to diabetes-related comorbidities.4
Of interest are the types of nutrition therapy interventions implemented, ie, reduced energy/fat intake, carbohydrate counting, simplified meal plans, healthy food or exchange choices, use of insulin-to-carbohydrate ratios, physical activity, and behavioral strategies. A unifying focus of nutrition therapy interventions for type 2 diabetes is a reduced energy intake and, for type 1 diabetes, adjusting insulin based on carbohydrate counting.2 It is essential that the person with diabetes be actively involved with health professionals to collaboratively develop appropriate nutrition interventions and an individualized eating pattern that they can implement. The ADA recommends that persons with diabetes receive individualized medical nutrition therapy as needed to achieve treatment goals, preferably by a registered dietitian/nutritionist familiar with the components of medical nutrition therapy in diabetes.3 Multiple encounters to provide education and counseling initially and on a continued basis are also essential.4
Diabetes nutrition education can also be provided as part of a comprehensive diabetes self-management and support program.3 Unfortunately, national data in the US indicate that only about a half of persons with diabetes receive diabetes education and even fewer see a registered dietitian/nutritionist.9 One study of over 18,000 people with diabetes revealed that only 9.1% had at least one nutrition visit within a 9-year period of time.10 It is likely the same problem exists in other countries as well. Disease self-management, support, and nutrition therapy are important components of diabetes care and necessary for improved outcomes in all people with the disease.11–14
Weight loss intervention
Overweight and obesity are common health problems in persons at risk for and with type 2 diabetes. Weight loss is frequently recommended as the solution to improve glycemic control.3 In persons with prediabetes, modest amounts of weight loss and regular physical activity are very effective in preventing or delaying the onset of type 2 diabetes.15 In individuals who have maintained lifestyle strategies for prevention of diabetes, the effectiveness of these strategies has been maintained for 10 years and longer.16 Weight loss interventions have also been shown to be effective in improving glycemic control in individuals with newly diagnosed diabetes.17,18
The benefit of weight loss interventions in type 2 diabetes of longer duration is controversial.19 The Academy of Nutrition and Dietetics reported that approximately half of the weight loss intervention studies in persons with type 2 diabetes achieved improvements in HbA1c at one year and one half did not.2 The ADA reported that in weight loss intervention studies lasting one year or longer in persons with diagnosed type 2 diabetes, modest weight losses ranged from 1.9 kg to 8.4 kg.3 The two interventions resulting in the largest amount of weight loss at one year were the Mediterranean-style eating pattern (−6.2 kg) in persons with newly diagnosed diabetes18 and the intensive lifestyle intervention in the Look AHEAD (Action For Health in Diabetes) trial (−8.4 kg), also in individuals who were early in the disease process.20 The other weight loss interventions reviewed by the ADA resulted in weight losses of 4.8 kg or less at one year.3 HbA1c levels improved at one year in six intervention groups; however, HbA1c levels at one year did not improve in six other intervention groups. Lipid and blood pressure outcomes from weight loss interventions were mixed.
The Look AHEAD trial20,21 deserves review. The objective was to determine if long-term weight reduction would reduce cardiovascular morbidity and mortality in people with type 2 diabetes. The trial was stopped early in September 2012 after 9.6 years; although intensive lifestyle intervention did no harm, it w