The role of dietary fat in the regulation of energy intake was assessed by manipulating a conventional diet and measuring spontaneous food consumption. Twenty-four women each consumed a sequence of three 2-wk dietary treatments in which 15-20%, 30-35%, or 45-50% of the energy was derived from fat. These diets consisted of foods that were similar in appearance and palatability but differed in the amount of high-fat ingredients used. Relative to their energy consumption on the medium-fat diet, the subjects spontaneously consumed an 11.3% deficit on the low-fat diet and a 15.4% surfeit on the high-fat diet (p less than 0.0001), resulting in significant changes in body weight (p less than 0.001). A small amount of caloric compensation did occur (p less than 0.02), which was greatest in the leanest subjects (p less than 0.03). These results suggest that habitual, unrestricted consumption of low-fat diets may be an effective approach to weight control.

Our conceptions of how malnutrition endured early in life affects brain development have evolved considerably since the mid-1960s. At that time, it was feared that malnutrition endured during certain sensitive periods in early development would produce irreversible brain damage possibly resulting in mental retardation and an impairment in brain function. We now know that most of the alterations in the growth of various brain structures eventually recover (to some extent), although permanent alterations in the hippocampus and cerebellum remain. However, recent neuropharmacological research has revealed long-lasting, if not permanent, changes in brain neural receptor function resulting from an early episode of malnutrition. These more recent findings indicate that the kinds of behaviors and cognitive functions impaired by malnutrition may be more related to emotional responses to stressful events than to cognitive deficits per se, the age range of vulnerability to these long-term effects of malnutrition may be much greater than we had suspected and the minimal amount of malnutrition (hunger) necessary to produce these long-term alterations is unknown.

This study examined the degree to which humans compensate for a reduction in dietary fat by increasing energy intake. Thirteen females were randomly assigned to either a low-fat diet (20-25% of calories as fat) or a control diet (35-40% fat) for 11 wk. After a 7-wk washout period, the conditions were reversed for another 11 wk. Energy intake on the low-fat diet gradually increased by 0.092 kJ/wk resulting in a total caloric compensation of 35% by the end of the 11-wk treatment period. This failure to compensate calorically on the low-fat diet resulted in a deficit of 1.22 kJ/d and a weight loss of 2.5 kg in 11 wk, twice the amount of weight lost on the control diet. These results demonstrate that body weight can be lost merely by reducing the fat content of the diet without the need to voluntarily restrict food intake.

The behavioral effects of early malnutrition and early environmental isolation were observed in male rats. Dietary and environmental manipulations occurred during the first 7 weeks of life, after which followed a 10-week recovery period. On the basis of several different responses, it was found that the behavioral effects of early malnutrition were exaggerated by the environmental isolation. In most cases, the behavioral effects of early malnutrition were completely eliminated by supplying "additional stimulation" early in life. Two theoretical mechanisms are proposed to explain these findings.

Young and Nestle suggested that the increase in the portion size of food products evident in the United States during the past 20 years may be responsible for the epidemic of overweight and obesity. They based their conclusion on statistical correlations. The purpose of the present study was to provide experimental evidence to support their proposal. Cornell undergraduate students were given access to a buffet lunch on Monday, Wednesday, and Friday and were told this was a test of flavor enhancers. They were instructed to eat as much or as little as they wanted. On the same days of the following week, the subjects were divided into 3 groups. Each group was served either 100%, 125%, or 150% of the amount of food they had consumed the previous week. When larger amounts were served, significantly greater amounts of food were consumed. Each of the 4 foods that comprised the meal (soup, pasta, breadsticks, ice cream) increased significantly in proportion to the portion size. The data clearly support the hypothesis proposed by Young and Nestle and support the powerful role that environment plays in determining energy intake and potential increases in body weight.