1a. Objectives (from AD-416)
1. Test the feasibility and effectiveness of a long-term caloric restriction intervention program for decreasing body fatness, risk factors for chronic disease, and retarding biological aging. 2. Examine the causes of error in the accuracy of reporting energy, macronutrient, and fiber intake from foods. 3. Assess whether a worksite intervention will result in a significant and sustainable reduction in the prevalence of overweight and obese employees and disease risk factors compared to a control group receiving no intervention. 4. Examine the contributions of heritable and environmental factors to eating behaviors and dietary patterns associated with weight gain and body fatness.
1b. Approach (from AD-416)
The etiology and effective prevention of adult-onset weight gain remains poorly understood. In addition, there is little information on the effects of calorie restriction designed to reduce body weight on biological parameters related to aging. These questions will be addressed in a series of 4 studies designed to contribute to understanding the process of dietary change and effective methods for long-term weight control and their effects on long-term health. These will include a randomized controlled trial of human caloric restriction (CALERIE) examining the metabolic effects of a 25% reduction in energy intake for 2 years, a trial of low and high fat diets on weight change in relation to insulin secretion status, a genetic analysis of the heritability of body fat and related parameters in identical twins reared together or reared apart, and an intervention to examine the feasibility of changing dietary Disinhibition in free living individuals and the impact of such a change in body weight.
3. Progress Report
As planned, in FY-09 we completed recruitment for our multi-site CALERIE study of the long-term effects of reduced energy intake on metabolic aging in humans (Objective 1). We now have the full cohort for this major randomized control trial completed and are continuing to study our population as they move through the program. Final measurements will be taken on the last subjects in August 2011, after which time we will be working with our co-investigators at the other multiple sites to analyze the data for publication. Ongoing quality control is documented by an external monitoring group and has been shown to be outstanding at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts. For example, 93% of randomized subjects complete the study, and we successfully collect 99.7% of metabolic rates (our primary outcome), 99.3% of body weights and 100% of heights. We also met our objectives for analysis of twin data (Objective 3). Specifically we have prepared databases for analysis of the heritability of health components and factors related to the heritability of body fatness. We have published our findings on the heritability of lipid values, and now have 2 papers ready for submission on the methodology of body composition assessments in twin studies and the heritability of eating behavior. The results that have been obtained emphasize that, while heritability is clearly important, environmental (i.e. modifiable) factors can have a major impact on risk of obesity and risk factors for chronic disease. Objective 2 changed during the last year. This objective originally focused on the role of insulin secretion status and did not receive funding as described above. While we would have wished to continue this project with funding, we noted that having another group replicate our findings exactly is a legitimate reason to refocus this objective to an area where more data are needed. We have therefore requested permission to substitute a new objective regarding the accuracy of dietary energy reporting in packaged foods and restaurant meals. We have preliminary data for this new objective, described below, that indicates further studies are urgently needed to examine the overall accuracy and individual variability in energy reporting. Objective 3 changed during the past year. Originally this objective concerned an intervention for preventing weight gain through changing counterproductive eating behaviors such as 'disinhibition'. In view of the increasing national interest in practical community programs for obesity prevention, we have reformulated our intervention plans and obtained pilot funding for a comprehensive intervention that is intended for worksite delivery for improving population weight control. We have successfully recruited our worksites for this project, and will be initiating the intervention during the coming year. For publications related to this project, see parent project #1950-51000-071-00D.