EBM Tools for Practice: Weight Management: Evidence-Based Nutrition Strategies

Introduction:
Obesity is a complex multifactoral chronic disease that develops from an interaction between genetics and the environment. The development of obesity involves the integration of social, behavioral, cultural, physiological, metabolic and genetic factors. Treatment of obesity should be based on a comprehensive weightmanagement program to produce weight loss, prevent further weight gain and maintain weight loss over a prolonged period. Overweight is currently defined as a body mass index (BMI) of 25 to 29.9 and obesity as a BMI of >30. But BMI may not correspond to the same degree of fatness in different populations, and health risk may differ for different populations.

Obesity is associated with increased morbidity and mortality. Scientific evidence supports the effectiveness of weight loss in the reduction of risk factors for diabetes and cardiovascular disease among people who are overweight or obese.

National evidence-based guidelines recommend diet therapy as an integral component of a comprehensive weightmanagement program. Based on the client’s treatment plan and comorbid conditions, other nutrition practice guidelines – such as hypertension, type 2 diabetes mellitus, childhood overweight and nutrition care in bariatric surgery – may be needed to provide optimal treatment.

Strategies for Weight Loss and Maintenance include:

• Dietary therapy
• Physical activity
• Behavior therapy
• "Combined" therapy
• Pharmacotherapy
• Weight-loss surgery

Evidence-based nutrition recommendations are developed through the use of systematically reviewed scientific evidence in making food and nutrition practice decisions by integrating the best available evidence with professional expertise and client values to improve outcomes.

The Academy of Nutrition and Dietetics Evidence Analysis Library (EAL) provides a series of evidence-based guidelines describing the treatment of obesity. Each recommendation is rated according to the strength of the supporting evidence (Table 1) and based on the benefits versus harms of implementing the recommendation.

Strong evidence is available for the following recommendations:

• Medical Nutrition Therapy (MNT) for weight loss should last at least 6 months or until weight-loss goals are achieved, with implementation of a weight-maintenance program after that time. A greater frequency of contacts between the patient and practitioner may lead to more successful weight loss and maintenance.
• Individualized goals of weight-loss therapy should be to reduce body weight at an optimal rate of 1 to 2 pounds per week for the first 6 months and to achieve an initial weight-loss goal of up to 10% from baseline. These goals are realistic, achievable and sustainable.
• Estimated energy needs should be based on resting metabolic rate RMR. If possible, RMR should be measured (e.g., indirect calorimetry). If RMR cannot be measured, then the Mifflin-St. Jeor equation using actual weight is the most accurate for estimating RMR for overweight and obese individuals.
• An individualized reduced-calorie diet is the basis of the dietary component of a comprehensive weigh-management program. Reducing dietary fat and/or carbohydrates is a practical way to create a caloric deficit of 500- 1,000 kcals below estimated energy needs and should result in a weight loss of 1 to 2 pounds per week.
• Total caloric intake should be distributed throughout the day, with the consumption of 4 or 5 meals/snacks per day, including breakfast. Consumption of greater energy intake during the day may be preferable to evening consumption.
• For people who have difficulty with self-selection and/or portion control, meal replacements (e.g., liquid meals, meal bars, calorie-controlled packaged meals) may be used as part of the diet component of a comprehensive weight-management program. Substituting one or two daily meals or snacks with meal replacements is a successful weightloss and weight-maintenance strategy low glycemic index diet is not recommended for weight loss or weight maintenance as part of a comprehensive weight-management program, because it has not been shown to be effective in these areas.
• Physical activity should be part of a comprehensive weight-management program.
• Behavior therapy in addition to diet and physical activity leads to additional weight loss. Continued behavioral interventions may be necessary to prevent a return to baseline weight.

Fair evidence is available for the following recommendations:

• Portion control should be included as part of a comprehensive weightmanagement program. Portion control at meals and snacks results in reduced energy intake and weight loss.
• Having patients focus on reducing carbohydrates rather than reducing calories and/or fat may be a shortterm strategy for some individuals. Research indicates that focusing on reducing carbohydrate intake (<35% of kcals from carbohydrates) results in reduced energy intake. Consumption of a low-carbohydrate diet is associated with a greater weight and fat loss than traditional reduced-calorie diets during the first six months, but these differences are not significant after one year.

The key to achieving and maintaining a healthy weight is about a lifestyle that includes enjoyable and healthful foods, regular physical activity and balancing the number of calories you consume with the number of calories your body uses.

© 2006. Academy of Nutrition and Dietetics. Reprinted with permission.

Disclosure statement: Dr. Karmally has received honoraria from the American Pistachio Growers and the Sesame Workshop.