Karl, J. Philip; Roberts, Susan B; Schaefer, Ernst J; Gleason, Joi A; Fuss, Paul; Rasmussen, Helen; Saltzman, Edward and Das, Sai Krupa (2015) Obesity Volume 23, Issue 11, pages 2190–2198
OBJECTIVE: To examine the effects of dietary carbohydrate composition on body composition and metabolic adaptation during and after weight loss.
DESIGN: Four phase study: 5-week weight maintenance period (Phase 1); 12-week dietary assignment in which participants were randomised to one of four provided-food diets (Phase 2) of differing percentage energy from carbohydrate (55% or 70%) and GI (low or high) but matched for protein, fibre and energy; 5-week weight maintenance period with provided-food diets (Phase 3) and a 12-month follow-up period (Phase 4). Body weight and composition, resting metabolic rate (RMR) and metabolic adaptation (measured RMR-predicted RMR) were measured during weight loss and subsequent weight maintenance. Participants visited the study centre 3-5 days/week during Phase 1 and 3 days/week during Phases 2 and 3. Phase 4 involved monthly calls and quarterly visits.
SETTING: Boston, Massachusetts, USA.
PARTICIPANTS: Obese men and postmenopausal women (n=91), aged 45-65 years, BMI 28-38 kg/m2.
MAIN OUTCOME MEASURES: RMR, weight and body composition, metabolic adaptation (calculated as the difference between measured RMR and predicted RMR by phase).
RESULTS: Neither dietary GI nor % dietary energy from carbohydrate affected the quality of weight loss (in relation to fat free mass (FFM) and fat mass (FM)). In total the group lost 7.5% of initial body weight (95% CI: -8.4%-6.6%; P <0.001). Total weight loss did not vary by carbohydrate content (P=0.60), by GI (P=0.52) or across groups (P-interaction=0.69). Measured RMR was significantly lower (-226 kJ/day [95% CI: -314 to -138 kJ/day], P < 0.001) than predicted RMR following weight loss, but this difference was attenuated after 5 weeks of weight stability. Metabolic adaptation did not differ by dietary carbohydrate or GI level and was not associated with weight regain 12 months later.
CONCLUSIONS: Moderate-carbohydrate and low-GI diets compared with high-carbohydrate and high-GI diets did not demonstrate differences for preserving FFM or reducing metabolic adaptation during weight loss, when confounding dietary factors were controlled. Metabolic adaptation following weight loss was not a predictor of weight gain over the 12 month follow-up period.
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