Changes in weight loss, body composition and cardiovascular disease risk after altering macronutrient distributions during a regular exercise program in obese women
 
 
Journal Title (Medline/Pubmed accepted abbreviation): Nutr J
Year: 2010
Volume: 9
Number:
Page numbers: 59
doi: 10.1186/1475-2891-9-59

Summary of Background and Research Design

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:
 
 
Phase 1 (1 week)
Phase 2 (9 weeks)
Phase 3 (4 weeks)
Diet + Exercise Group
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.

Summary of research findings:
  • No group × time interaction was demonstrated for changes in caloric intake (P = .87; normalized to body mass changes and baseline dietary intake) or waist circumference (P = .22).
    • Protein intake was increased in the VLCHP and LCMP groups compared with HCLP (P < .05).
    • However, all dieting plus exercise groups reduced waist circumference from baseline at 10 weeks (P < .001 for all groups).
  • A significant group × time interaction was demonstrated for body mass (P < .005).
    • All dieting plus exercise groups reduced body mass from baseline at 1 week (P < .001 for all groups), which was further reduced at 10 weeks (P < .001 for all groups) and maintained at 14 weeks.
  • A significant group × time interaction was demonstrated for fat-free and fat mass (P < .05 for both).
    • Significant within-groups changes for fat-free mass were limited to the VLCHP group (at week 1) and the HCLP group (at weeks 1 and 10).
    • Significant within-groups changes for fat mass were observed in all dieting groups.
  • A significant group × time interaction was demonstrated for resting energy expenditure (P < .01).
    • Caloric restriction initially reduced energy expenditure, but all groups, except for CON, increased resting energy expenditure from baseline after 10 weeks.
  • A significant group × time interaction was demonstrated for maximal aerobic capacity (P < .05).
  • No group × time interaction was demonstrated for muscular strength or endurance
    • All dieting plus exercise groups increased muscular endurance from baseline (P < .001 for all groups).
  • No group × time interaction was demonstrated for lipid panel constituents, insulin, glucose, and HOMA-IR (homeostatic model assessment of insulin resistance)
    • Serum insulin and HOMA-IR values decreased in the VLCHP group at 10 and 14 weeks (P < .05 for both). The group x time interaction, however, was not significant in either case (P = .46 and P = .55 for insulin and HOMA-IR, respectively)
  • A significant group × time interaction was demonstrated for serum leptin (P < .05).
    • All dieting plus exercise groups had decreased leptin levels at 14 weeks (P = .05 for all groups).

Interpretation of findings/Key practice applications:

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.
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