Dieting has been reported to reduce resting energy expenditure, thereby increasing the prevalence of weight gain after weight loss. Intermittent dieting during a weight loss and exercise program may help minimize these adverse effects.
PURPOSE: To examine the efficacy of diet cycling with varying macronutrient diet compositions during an exercise and weight loss program on selected markers of health and fitness.
METHODS: 38 overweight, sedentary women (35±8 yr; 85±19 kg; 43±4% fat, 33±6 kg/m2) were assigned to a high carbohydrate (HC: n=20) or high protein (HP: n=18) diet group. During the first 30-days, subjects consumed 1,200 kcal/d for 1-wk, followed by 1,500 kcal/d for 3-wks. Subjects then followed a 2,200 kcal/d maintenance diet (4-wks) before repeating the 30-day cycle. Diets were 45:30:25% or 30:45:25% carbohydrate, protein and fat, respectively, for the HC and HP groups. Subjects also participated in the Curves™ circuit training program (3-d/wk), and walked briskly for 30-min (3-d/wk). Body composition, resting heart rate, blood pressure, peak VO2, GXT max time, 1RM strength, and muscle endurance tests were obtained at 0, 3, and 6 months. Data were analyzed by MANOVA with repeated measures, and are presented as means ± SD changes from baseline after 3 and 6 months, respectively.
RESULTS: Training and dieting decreased total body mass (-4.1±3.4, -5.2±4.9 kg, p=0.001), fat mass (-2.7±2.1, -3.5±3.4 kg, p=0.001), lean mass (-1.2±1.9, -1.2±1.9 kg, p=0.001), SBP (-3.6±10, -2.9±10%, p=0.08), DBP (-1.7±14, -3.5±14%, p=0.14); and, increased peak VO2 (9.7±17, 11.7±19%, p=0.001), time to peak VO2 (39.7±49, 45.0±65 s, p=0.001), leg press 1RM (13.8±24, 14.5±23%, p=0.002), and bench press 1RM (6.7±10, 5.1±12%, p=0.03). The HP diet was more effective in lowering resting HR compared to the HC diet (p=0.03). Neither upper nor lower muscular endurance was significantly improved.
CONCLUSION: Short-term diet cycling during a weight loss and exercise program may be an effective way to improve body composition, promote favorable hemodynamic changes, and improve VO2, as well as upper and lower body strength.
Supported by Curves International, Waco TX.