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. 5. Assess whether an intervention implemented during pregnancy will result in a significant and sustainable reduction in the prevalence of overweight and obese prior to and subsequent to delivery compared to a control group receiving no intervention.
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 Objective 1, the database for the landmark CALERIE study of human caloric restriction has been locked, and first papers describing the conduct of this study are now in press. This is the first randomized controlled trial of human caloric restriction, and the biological markers of aging that are being measured include immune function, inflammatory factors, body temperature, thyroid hormone axis and standard chronic disease risks factors. The importance of this accomplishment is major: the study is the only randomized clinical trial of human caloric restriction, and the study is implementing the largest weight loss goal of any study to date. The results from this trial will be far-reaching with respect to recommendations on caloric restriction and weight loss for long-term health. From this study is part of a four-site multi-site trial throughout the U.S. and analysis plans for the main study outcomes are currently being prepared and analysis will begin in the next year together with the writing of outcome papers. For Objective 2 we completed an analysis of data in the national nutrition database (SR-24) that had named restaurant foods and measured calorie contents and published the results in the Journal of the American Medical Association. This data replicated our previous finding that foods with low stated energy contents have higher measured energy contents than stated, which was also published in the Journal of the American Medical Association in 2011. That study shows that average restaurant-listed calories are accurate, but individual values are variable and in some cases differ considerably from laboratory-measured values. The inaccuracy is worst for foods with low stated calories, which may hamper consumer efforts to self-monitor calories for weight control. For Objective 3, we have entered the data for our worksite weight control intervention, cleaned and locked the data and analyzed the primary outcome in preparation for submission of papers. This worksite weight control intervention, in which four Boston worksites were enrolled in a randomized controlled trial of a 6-month weight control intervention delivered at the worksite, has achieved greater mean weight loss than any previous randomized controlled worksite trial in North America, and attrition was extremely low in the intervention group (11%), suggesting that the intervention is highly acceptable to participants. Finally, we have also added a new objective, concerning adaptation of our successful worksite weight control intervention to prevent excess weight gain in pregnancy. This study was successfully funded as a pilot during the past year. Institutional Review Board permission has just been obtained so recruiting will begin shortly.
1. The accuracy of calories listed in restaurants. There is little information on the accuracy of information on the calorie contents of commercial foods as provided by the vendors. ARS–funded researchers at the JM USDA Nutrition Center at Tufts University, Boston, Massachusetts have conducted a series of studies on the accuracy of published food composition values. Food samples from a variety of restaurant and packaged foods at 3 locations across America (MA, IN, AR) were collected and the samples were analyzed for energy content so that values could be compared to stated values. There was no significant difference between measured and stated values; however, the accuracy of individual stated food energy contents varied widely and foods with low stated energy values contained significantly more energy than stated. In a separate analysis of measured energy data from the national nutrient database (SR-24) a similar finding was reported. These studies highlight the need for more accurate and precise information on the energy contents of different foods, because without such information consumers cannot self-monitor calorie intake to prevent obesity.
2. Heritability of Body Fatness and Eating Behaviors. There is great uncertainty over the extent to which body weight, body fatness and eating behaviors are heritable. However, such information is important because it helps define the extent to which weight management interventions can be successful, and identifies targets to focus on for behavior changes that can help prevent obesity. ARS-funded researchers at the JM USDA Nutrition Center at Tufts University, Boston, Massachusetts showed for the first time that the methodology by which body composition is measured has a significant impact on estimates of heritability of body fatness, and that the methods with least bias show that heritability is relatively low. Thus, shared and unique environmental factors are important determinants of an individual’s body fatness. The studies also showed that the eating behavior construct ‘disinhibition’ is not very heritable, suggesting that this variable, which is known to have a significant impact on body fatness, may be susceptible to modification in behavior change programs.