Metabolic and behavioral effects of a high-sucrose diet during weight loss.

In response to evidence linking obesity and high amounts of dietary fat, the food industry has developed numerous reduced-fat and nonfat food items. These items frequently derive a relatively large percentage of their energy from sugars and the effect of these sugars on weight regulation is not well known. We studied the comparative effects of high- and low-sucrose, low-fat, hypoenergetic diets on a variety of metabolic and behavioral indexes in a 6-wk weight-loss program. Both diets contained approximately 4606 kJ energy/d with 11% of energy as fat, 19% as protein, and 71% as carbohydrate. The high-sucrose diet contained 43% of the total daily energy intake as sucrose; the low-sucrose diet contained 4% of the total daily energy intake as sucrose. Twenty women aged 40.6 +/- 8.2 y (mean +/- SD) with a body mass index (in kg/m2) of 35.93 +/- 4.8 consumed the high-sucrose diet; 22 women aged 40.3 +/- 7.3 y with a body mass index of 34.93 +/- 4.4 consumed the low-sucrose diet. Mixed-design analysis of variance showed a main effect of time (P < 0.01), with both diet groups showing decreases in weight, blood pressure, resting energy expenditure, percentage body fat, free triiodothyronine (FT3), urinary norepinephrine, and plasma lipids. Small but significant interactions were found between group and time in total cholesterol (P = 0.009) and low-density lipoprotein (LDL) (P = 0.01). Both groups showed decreases in depression, hunger, and negative mood, and increases in vigilance and positive mood with time (P < 0.01). Results showed that a high sucrose content in a hypoenergetic, low-fat diet did not adversely affect weight loss, metabolism, plasma lipids, or emotional affect.

The role of motor activity in diet-induced obesity in C57BL/6J mice.

Previous research in our laboratory has demonstrated that the C57BL/6J (B/6J) mouse has a predisposition to develop severe obesity if placed on a high-fat diet. In the present study we assessed the role of physical activity in this phenomenon. Obesity-prone B/6J and obesity-resistant A/J mice were placed on one of four diets; high fat/high sucrose, high fat/low sucrose, low fat/high sucrose, and low fat/low sucrose. After 4 months, all animals on the high-fat diets had gained more weight than animals on the low-fat diets, and this phenomenon was greatly exaggerated in B/6J mice. Despite the fact that B/6J mice gained more weight than A/J mice on high-fat diets without consuming more calories, spontaneous motor activity was elevated in B/6J mice compared to A/J mice. There was no effect of the diets on activity either within or across strains. These data suggest that predisposition to diet-induced obesity is not explainable by reduced levels of physical activity.

Effect of meal pattern during food restriction on body weight loss and recovery after refeeding.

The present study was designed to assess whether the pattern of meal feeding and the degree of caloric restriction have an effect on the body weights and refeeding patterns of restricted 4-month-old Long-Evans rats, relative to ad lib-fed controls. Four experimental groups of rats (n = 6 each) were put on different paradigms of food restriction, and a fifth group fed ad lib throughout served as controls. Twelve rats were restricted to receiving 50% of their mean baseline food intake, and 12 rats received only 70% of their baseline food intake. Each experimental group was further subdivided with one subgroup receiving all of their calories in one meal/day and the other with caloric intake equally divided into two meals/day. There was no statistical difference in the final body weights of the restricted groups. Although there appeared to be identical patterns of weight regain, none of the restricted groups ever reached the mean body weight of the controls because of an asymptotic leveling off of rate of body weight regain. Rats that had received 50% of baseline calories as two meals/day had significantly more adipose mass than did any other group. The present findings suggest that in the rat, refeeding and, hence, regulation, occurs to normalize rate of weight gain rather than absolute body weight.