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What is the relative effectiveness for long-term weight loss of energy-reduced diets that differ in their targets for intake of fat, protein, and carbohydrates?
randomised controlled trial. ClinicalTrials.gov NCT00072995.
blinded (participants, investigators, data collectors, and outcome assessors).
2 university hospitals in the USA.
811 overweight or obese adults 30–70 years of age (mean age 51 y, 64% women) with body mass index 25–40 kg/m2 (mean 33). Exclusion criteria included diabetes, unstable cardiovascular disease, and insufficient motivation.
assignment to 1 of 4 diets: low-fat, average-protein (20% fat, 15% protein, 65% carbohydrates) (n = 204); low-fat, high-protein (20% fat, 25% protein, 55% carbohydrates) (n = 202); high-fat, average-protein (40% fat, 15% protein, 45% carbohydrates) (n = 204); or high-fat, high-protein (40% fat, 25% protein, 35% carbohydrates) (n = 201). Daily meal plans were provided. All diets adhered to principles of a healthy diet and were recommended for long-term weight loss. Participants attended regular group and individual sessions to promote adherence, were encouraged to participate in moderate exercise for 90 minutes/week, and self-monitored food intake and exercise using a web-based tool.
change in body weight and waist circumference. Effects of fat and protein levels were analysed in a 2 × 2 factorial manner; the effect of carbohydrate level was compared between the 2 diets with the highest and lowest levels.
80% (intention-to-treat analysis; missing data were imputed).
Mean weight loss (about 6 kg at 6 mo and 3.5 kg at 24 mo) and temporal pattern of weight change (rapid loss in the first 6 mo and a gradual increase after 12 mo) were similar with the 4 diets. The table shows weight loss by levels of the 3 macronutrients. Groups did not differ for change in waist circumference.
Energy-reduced diets with different targets for intake of fat, protein, and carbohydrates achieved and maintained similar levels of moderate weight loss in overweight and obese adults when accompanied by reinforcement through behavioural counselling.
Sacks FM, Bray GA, Carey VJ, et al. Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates. N Engl J Med 2009;360:859–73.
Clinical impact ratings: Family/general practice 6/7; General/internal medicine 5/7; Obesity 6/7
Obesity is increasingly prevalent, yet little research is available to establish the benefits of different macronutrient diets on weight loss over time. Systematic reviews have confirmed the long-term benefits of interventions such as exercise and behaviour therapy for obesity1 and suggest no difference in weight loss when low-fat and low-caloric diets were compared over 18 months.2 The randomised trial by Sacks et al showed that overall caloric reduction, supported by behaviour therapy and moderate exercise, resulted in weight loss and improvements in cardiovascular risk factors for ⩽2 years.
The strength of the study is that moderate weight loss was achieved through manipulation of macronutrient content rather than specific food types. However, the hospital-based settings in north-eastern and southern USA point to resources that may not be widely available. Furthermore, lack of detailed descriptions of behaviour support strategies and their resource intensity may limit replicability in practice, although correspondence with the authors may overcome this issue.
The trial by Sacks et al is relevant to nurses involved in population health strategies and those working with adults needing to lose weight and reduce risk of cardiovascular disease and metabolic syndrome. The results showed that approaches to weight loss can be simplified by focusing on energy-reduction diets, coupled with behaviour support and moderate physical activity throughout the weight-loss and maintenance periods, and can be used with diverse populations. Application of results to disease-specific weight-loss interventions must be approached cautiously. Methods used to integrate the results into care will be dependent on an individual’s needs and setting.
Sources of funding National Heart, Lung, and Blood Institute and General Clinical Research Center, National Institutes of Health.
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