Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 26, 1996
Publication Date: N/A
Interpretive Summary: Obesity is one of the most pervasive public health problems in the United States. Although the restriction of calories and fat in the diet is an effective means for achieving weight loss, very little is known regarding the role of other specific dietary factors in promoting loss of excess body fat and preservation of lean body tissue during weight loss. Certain aspects of eating behavior, such as the time of day that meals are ingested, may have important consequences for achieving a healthy body weight. We studied over weight women during a weight loss program that combined a calorie-restricted diet and regular exercise. By altering the size of morning and evening meals, we found that more weight was lost when larger morning meals were ingested. However, the additional weight loss ascribed to the larger morning meal regime was the result of lean body tissue loss, not body fat loss. When larger evening meals were ingested, more lean body tissue was preserved. Incorporating larger evening meals into a weight loss regime may be important in minimizing the loss of lean body tissue during weight loss and should be considered when designing diets for weight loss.
Technical Abstract: The purpose of this study was to determine if meal ingestion pattern (larger morning meals [AM] vs. larger evening meals [PM] affects changes in body weight, body composition, or energy utilization during weight loss. Ten women completed a metabolic ward study of 3-wk of weight stabilization followed by 12-wk of weight loss with a moderate energy-restricted diet and dregular exercise. The weight loss phase was divided into two 6-wk periods During period 1, 70% of daily energy intake was taken as two meals in the AM (n=4) or in the PM (n=6). Subjects crossed over to the alternate pattern in period 2. Both weight loss and fat-free mass loss were greater with the AM than the PM pattern: 3.90+/-0.19 vs. 3.27+/-0.26 kg/6 wk, p< 0.5, and 1.28+/-0.14 vs. 0.25+/-0.16 kg/6 wk, p<0.001, respectively. change in fat mass and loss of body energy were affected by order of meal pattern ingestion. The PM pattern resulted in greater loss of fat mass in period 1 (p<0.01) but not in period 2. Likewise, resting mid-afternoon fa oxidation rate was higher with the PM pattern in period 1 (p<0.05) but not in period 2, corresponding with the fat mass changes. To conclude, meal pattern manipulations appeared to have minimal, if any, impact on loss of body fat mass or fat oxidation rate. Ingestion of larger AM meals resulted in slightly greater weight loss, but ingestion of larger PM meals resulted in better maintenance of fat-free mass. Thus, incorporation of larger PM meals in a weight loss regime may be important in minimizing the loss of fat-free mass.