Journal Title (Medline/Pubmed accepted abbreviation): Nutr J
Page numbers: 59
Background: The prevalence of obesity in the US and throughout the world continues to increase with an estimated 1.2 billion people worldwide overweight. Much research is being conducted worldwide to help identify causative mechanisms as well as programs to better manage obesity progression. A higher protein intake for weight loss in overweight and obese populations has been indicated for many reasons, including a better regulation of glucose and insulin homeostasis and prevention of lean muscle loss. In addition to dietary modifications, the inclusion of more physical activity is often indicated to stimulate weight loss, increase energy expenditure, and promote improvements in insulin sensitivity as well as other indicators of cardiovascular disease risk.
Hypothesis:The authors hypothesized that: (1) participating in the diet and exercise programs would facilitate weight loss in addition to improvements in various indicators of health in comparison with the control groups; (2) dietary groups that contained higher amounts of dietary protein would experience smaller reductions in lean tissue mass in comparison to other diet groups; and (3) acute alterations would facilitate weight maintenance while allowing for periods of higher and lower caloric intake.
Subjects: One hundred forty-one sedentary, obese women (38.7 ± 8.0 yr, 163.3 ± 6.9 cm, 93.2 ± 16.5 kg, 35.0 ± 6.2 kg/m2, 44.8% ± 4.2% fat) participated in the study. Patients were excluded if they had any metabolic or cardiovascular disorder, if they had taken any ergogenic supplements within 6 months before study, of if they did not agree to restrict any other form of diet or exercise during the study.
Experimental design:Randomized, controlled
Treatments and protocol:
After baseline testing, participants were matched according to body mass and age into 1 of 6 groups and depending on group assignment transitioned through 3 phases of dieting plus exercise. Two control groups were used, a no exercise and no diet control group (CON) and an exercise-only (no diet) control group (ND). For the 4 groups on diet plus exercise, the diets were as follows:
|Diet + Exercise Group||Phase 1 (1 week)||Phase 2 (9 weeks)||Phase 3 (4 weeks)|
|kcal/day; % Carbohydrate:% Protein:% Fat|
|High energy, high carbohydrate, low protein (HED)||2,600;55:15:30||2,600;40:30:30||2,600;55:15:30|
|Very low carbohydrate, high protein (VLCHP)||1,200;7:63:30||1,600;15:55:30||2,600;55:15:30|
|Low carbohydrate, moderate protein (LCMP)||1,200;20:50:30||1,600;15:55:30||2,600;55:15:30|
|High carbohydrate, low protein (HCLP)||1,200;55:15:30||1,600;15:55;30||2,600;55:15:30|
After 0, 1, 10, and 14 weeks, all participants completed testing sessions that included anthropometric, body composition, energy expenditure, fasting blood samples, and aerobic and muscular fitness assessments. Blood was collected and assayed for a standard complete metabolic panel, thyroid panel, lipid panel, and clinical markers of protein and fatty acid metabolism. At 10 and 14 weeks, participants also completed a volitional maximal cardiopulmonary exercise test and 1-repetition maximum (1RM) assessments and maximal repetitions to fatigue test using 80% of their predetermined 1RM with both the bench press and leg press. Before each testing session, participants completed a 4-day food diary, fasted for 10 hours, and refrained from vigorous activity for 24 hours.
Key messages from this study: 1) Obese women undertaking a daily exercise program and following a restricted-energy diet had comparable improvements in body composition and general fitness and strength regardless of differences in macronutrient distribution; 2) Declines in resting energy expenditure that were initially observed in the energy-restricted groups eventually normalized by phase 3 of the study; and 3) Energy-restricted diets coupled with exercise tend to reduce fasting insulin and HOMA-IR scores, with possible increases in benefit deriving from replacement of carbohydrate with protein.