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
The Energy Metabolism Laboratory continued its projects investigating factors determining successful weight control in adults of different ages. The laboratory has had considerable success in all projects. In particular, it completed enrollment in two landmark studies this year. The first is a landmark study of a population of adults in a randomized controlled trial of human caloric restriction that is investigating whether reduction in energy intake by 25% causes changes in biological markers of aging that are indicative of improved lifespan and health in old age. This is the first randomized controlled trial of human caloric restriction, and biological markers of aging being measured including immune function, inflammatory factors, body temperature, thyroid hormone axis and standard chronic disease risks factors. Data from this study is part of CALERIE (Comprehensive Assessment of the Long-term Effects of Restricted Intake of Energy) a multi-site trial throughout the U.S. and is currently being entered, cleaned and locked for data analysis. This project contributes to efforts toward an important National Program goal namely, 2-A, to identify roles of food, nutrients, food components and physical activity in promoting health and preventing disease. The other study completed by the laboratory is a worksite weight control intervention, in which 4 Boston worksites were enrolled in a randomized controlled trial of a 6-month weight control intervention delivered at the worksite. That 6-month study was completed without attrition of any worksite and results are currently being entered for data analysis. This study findings will provide insight and help in contributing toward the National Program goal, 3-A, in understanding the causes and consequences of obesity and related disorders. Finally, the laboratory also completed two studies on the accuracy of reported calories in restaurant menus, one of which was previously published and the other has just been published in the July 2011 edition of The Journal of the American Medical Association. The most recent of this pair of studies shows that on average restaurant-listed calories are accurate, but individual values are variable and in some cases differ considerably from laboratory-measured values. In addition, restaurant purchased foods listing fewer than 625 calories per portion tend to provide more calories than stated and contributes to efforts toward two of the National Program goals namely, 1-C, to inform US food composition data and 1-D, to enhance the health promoting quality of the food supply.