Impact of Meal Frequency (3 vs. 6 meals/d) and Macronutrient Composition (high vs. low protein) on Resting Energy Expenditure in Men and Women
Dr. Paul Arciero
To measure the effects of different macronutrient diet compositions and glycemic indexes in combination with varying meal frequency (3 vs. 6 meals per day) on resting metabolic rate (RMR), postprandial thermogenesis (TEM), and plasma glucose in men and women. RMR, TEM, and plasma glucose levels are all important indicators that affect CVD and metabolic disease.
An independent groups, non-exercise controlled design was used. Participants' activity level was kept constant throughout the study. Subjects participated in a randomized study in which they followed one of the three specific diets for two months. The study was broken down into three separate phases. In the pre testing period, all participants were placed on a standardized diet (45% CHO, 25% PRO, 30% fat/3meals per day) for five days as a pre testing washout period. The pre testing wash out period ended on day 1, with the administration of a TEM meal of a macronutrient composition reflecting the baseline diet. In the weight maintenance phase, the participants were split into three groups: HP-6 (40% PRO, 40% CHO, 20% fat; 6 meals/day), FGP (15% PRO, 60% CHO, 25% fat; 3meals/day), HP-3 (40% PRO, 40% CHO, 20% fat; 3 meals/day). An energy balance was created basing their needs on the day -4 and day 1 RMRs and a 3-month physical activity questionnaire. The day 28 TEM meal reflected the meal size and composition the subject had been eating for the past month. The weight loss phase began after day 28 testing. Subjects were given a diet that represented a 25% caloric deficit from their weight maintenance diet. The day 56 TEM meal reflected the diet of the previous month. On TEM days, subjects arrived at 6:00, and were placed under the metabolic hood for a 20 minute resting measurement. This was followed by a VAS form and the meal; following the meal, subjects were placed under the hood for minutes 15-30, 45-60, 75-90 and VAS forms were filled out at times 30, 60, and 90 minute post meals.
All data was collected, entered and analyzed with SPSS v11.0 for windows. Statistical analysis was performed using a 3 groups (HP-6, FGP, HP-3) by 3 time points (Day 1, Day 28, Day 56) repeated measures analysis of variance (ANOVA) to determine significance within and between groups, and one-way ANOVAs were used for single time points among three groups to determine significance in SPSS 11.0. Significance was set at p<.05. All data is presented as mean ± SE. Results: No significant changes existed between the groups at baseline. In the HP-6 group kcals consumed during day 28 TEM meals decreased by 40.2% (p<.001) from baseline testing; and kcals consumed during Day 56 TEM meals decreased by 25% (p<.001) from day 28. In the FGP group kcals consumed during Day 28 TEM meals decreased by 3.7% (not significant) from baseline testing; and kcals consumed during Day 56 TEM meals decreased by 25% (p<.001) from Day 28. In the HP-3 group kcals consumed during Day 28 meals increased 3.7% (not significant) from baseline testing; and kcals consumed during Day 56 TEM meals decreased by 25% (p<.001) from Day 28. All three groups showed significant decreases in body weight between Day 1 to Day 56 and from Day 28 to Day 56. There were no significant differences in any of the groups between the amount of kcals burned per minute at time 0 between Day 1 to Day 28, Day 1 to Day 56, and Day 28 to Day 56. In the HP-6 group there was a significant increase in respiratory quotient from Day 1 to Day 28 (0.79±0.01 to 0.84±0.01; p<.05) and a significant decrease from Day 28 to Day 56 (0.84±0.01 to 0.78±0.02; p<.01). Day 56 RQ values were also significantly different (p<.05) between the groups. There were no significant differences in RQ values within both the FGP and HP-3 groups. No significant changes in total TEM kcals burned were found in the HP-6 group. The FGP group showed a significant decrease (120.55±10.2 to 113.31±10.1; p<.05) in total TEM kcals burned from Day 28 to Day 56. The HP-3 group showed a significant increase (116.0±4.5 to122.9±3.9; p<.05) from Day 1 to day 56; TEM kcals burned in the HP-3 group decreased with a strong trend (122.9±3.9 to 115.5± 4.8) from Day 28 to day 56. In the HP-3 group there was a significant increase in total kcals burned above resting kcals burned from Day 1 to Day 28 (13.7±2.7 to 22.1±1.4; (p<.01); the other groups showed no significant changes in total kcals burned above resting kcals burned. TEM ratio increased (.03±.02 to .06±.03 and 03±.02 to .07±.03; p<.05) in the HP-6 group from Day 1 to Day 28 and from Day 1 to Day 56 respectively. TEM ratio did not significantly change throughout the study in the FGP group; however, in the HP-3 group TEM ratio increased (.03±.02 to .04±.01; p<.05) from Day 1 to Day 28 and did not significantly change from Day 28 to Day 56. The HP-6 group showed a significant increase in absolute TEM from Day 1 to Day 28 (0.21±0.01 to 0.36±0.02 p<.001), as well as from Day1 to Day 56 (0.21±0.01 to 0.48±0.03; p<.001), and from Day 28 to Day 56 (0.36±0.02 to 0.48±0.03; p<.001). The other groups showed no significant changes in absolute TEM.
The findings from our study show the benefits of a diet involving six meals per day, a high % of protein, low % of CHO intake, and low GI-index foods on the body's ability to lose weight while increasing TEM. This is extremely important in a society where obesity, which leads to CVD and metabolic disease, is increasing at a faster rate than ever.