2007 Annual Report 1a.Objectives (from AD-416) To develop two healthy hypocaloric diets consistent with current dietary recommendations and compare them for their ability to promote long-term CR leading to body weight and fat losses over 1 year in overweight men and women. To test the hypothesis that there are metabolic and anti-aging benefits of long-term (2-year) calorie restriction (CR) in overweight men and women which are equivalent to the benefits seen in animal models, and which result in a delayed rate of biological aging. To quantify the relative associations of different dietary variables (including eating patterns and macronutrient composition), with energy intake and body fatness in free-living young and elderly adults. 1b.Approach (from AD-416) (1)Obesity and overweight are major public health problems, and are particularly prevalent among elderly adults. The overall goals will be to determine the etiology of weight gain at different adult ages, to develop improved methods for weight loss; and to quantify the potential metabolic benefits and risks of a caloric restriction(CR) program designed to delay biological aging in humans. In particular, a sustainable diet will be developed that can be consumed at 30% less than baseline energy requirements for 1 year and measure its effects on body composition and energy expenditure, and will use that diet to examine the feasibility and metabolic effects of 30% & 20% CR over 2 years. In addition, we will analyze national cohort data to identify and quantify the relative effects of different dietary variables on energy intake and body mass index, including dietary fat, dietary glycemic index(GI), dietary fiber, and variety. 4.Accomplishments 1)Dietary Glycemic Load and Weight Loss Whether some diets work better for weight loss remains very controversial. The Energy Metabolism Laboratory has found that conventional ‘high glycemic load’ (i.e. low fat) diets result in equivalent mean weight loss to the low glycemic load diets that are the basis for several popular diet programs. In a carefully controlled 12 month study in which food was provided to participants for the first 6 months, there was no effect of dietary composition on weight loss, and mean values for weight loss at 12 months were almost identical in the two groups. In addition, there were no significant differences between the groups in self-reported hunger, satiety and satisfaction with the provided diet. These results provide strong support for the notion that a range of dietary compositions are compatible with sustained weight loss and that low glycemic load diets are not on average more effacious than conventional high glycemic load diets. These results will help national committees formulate recommendations on dietary intake during weight loss. This accomplishment is aligned with NP107 Human Nutrition Program Component 6-Prevention of Obesity and Disease: Relationship between Diet, Genetics, and Lifestyle. 2) Dietary Composition and Food Cravings Food cravings are very common and may contribute to weight gain, with approximately 90% of adults experiencing strong urges to eat particular foods on a regular basis. However, the underlying reasons for cravings are not well understood. The Energy Metabolism Laboratory has shown that cravings occur reproducibly for foods that are high in energy and low in fiber; in contrast to previous assumptions that cravings were primarily for food high in carbohydrate this research demonstrated that all macronutrients are associated with cravings and that caloric density is the single most defining feature of foods that are craved. In addition, in a weight loss study, it was demonstrated that food cravings do not diminish with weight loss, rather individuals who are successful at losing weight are those who give into their food cravings less frequently. This research identifies the frequency of giving into cravings as an important issue for addressing in weight control programs. This accomplishment is aligned with NP107 Human Nutrition Program Component 6-Prevention of Obesity and Disease: Relationship between Diet, Genetics, and Lifestyle. 3) Dietary Carbohydrate Intake, Insulin Secretion and Weight Loss Insulin resistance is a common metabolic problem associated with excess body weight and leads to heath risks including type 2 diabetes. Whether dietary composition has benefits for insulin sensitivity during weight loss is not certain. The Energy Metabolism Laboratory has found that insulin secretion in response to a standard oral glucose tolerance tests improves substantially with weight loss and that the improvement is independent of the type of diet consumed during weight loss. Previous studies have suggested additional metabolic benefit of low glycemic index or low glycemic load diets; this carefully controlled study indicates that the benefits of weight loss outweigh the benefits of specific types of diets. This is an important finding as it helps emphasize that a broad range of healthy dietary compositions improve insulin sensitivity. This accomplishment is aligned with NP107 Human Nutrition Program Component 6-Prevention of Obesity and Disease: Relationship between Diet, Genetics, and Lifestyle. 4) Screening Implausible Data in Dietary Record Analysis There have been many inconsistent studies published on the relationship between dietary composition and body fatness. The Energy Metabolism Laboratory has demonstrated that screening implausible records out of dietary databases improves the correlation between BMI as dietary parameters such as dietary fiber. These results demonstrate that methodological issues may have contributed to the previous controversies and that when dietary data are screened using new statistical techniques the relationship between diet and fatness become much more reproducible and consistent with the putative biological effects of different dietary macronutrients. This work lends further weight to the notion that dietary macronutrient composition does significantly impact energy intake and body fatness, and thus the findings will be useful for evaluating data from different studies. This accomplishment is aligned with NP107 Human Nutrition Program Component 6-Prevention of Obesity and Disease: Relationship between Diet, Genetics, and Lifestyle. 5)Physical Activity and Body Weight The effect of physical activity on body weight and fatness has remained controversial, with some studies suggesting substantial beneficial effects and others suggesting negligible or small effects. In a comprehensive review of the literature on exercise and energy regulation, the Energy Metabolism Laboratory has demonstrated very consistent but typically modest effects of physical activity interventions on body fatness, with similar magnitude of effects occurring with different types of exercise if level of energy expenditure is comparable. The results also show that cross-sectional studies indicate a larger effect of physical activity on body fatness but this is because individual variability in physical activity level is far greater cross-sectionally than the amount of exercise introduced in exercise intervention studies to date. These studies indicate that exercise interventions typically have a modest effect on body weight and fatness in adult men and women. This accomplishment is aligned with NP107 Human Nutrition Program Component 6-Prevention of Obesity and Disease: Relationship between Diet, Genetics, and Lifestyle. 5.Significant Activities that Support Special Target Populations None. 6.Technology Transfer Number of non-peer reviewed presentations and proceedings 7 Number of newspaper articles and other presentations for non-science audiences 15