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.
1. The stated energy contents of packaged foods and restaurant meals are frequently inaccurate. This topic has become an important public health issue with the issuance of new government directions to increase information available to consumers and increasing interest in ways to help individuals control their weight. If information is to be provided to consumers, the information should be accurate so that values provided are not misleading. ARS Funded Researchers from Tufts University in Boston, MA examined the accuracy of reported energy values in packaged frozen meals and restaurant foods in the Greater Boston area by collecting a convenience sample of foods and measuring energy content by adiabatic bomb calorimetry. We found that there was substantial variability in the accuracy of reported energy contents that far exceeded the measurement error for dietary energy, and on average both package foods and restaurant meals tended to have more energy than reported. Results from this study will improve accuracy of information provided to the public with regard to calorie content of food, which will help in making better food choices and in reducing the burden of obesity.
2. Moderate-energy-restriction diets result in more consistent weight control compared to low-energy restriction diets. We examined whether low or moderate energy restriction might be most effective for sustainable weight control. ARS Funded Researchers from Tufts University in Boston, MA studied 46 overweight men and women who were recommended to follow a diet with either 10% or 30% reduced energy for 1 year. There was no significant difference in weight or body fat loss between the two groups, but greater variability in weight loss in the 10% group, indicating that low energy restriction is effective for weight control in some individuals but not in others. These results demonstrate for the first time that the optimal level of energy restriction for effective weight control may differ between individuals and that, contrary to previous speculation, low-energy restriction does not appear to be more successful long-term than moderate-energy restriction.
3. A low dietary glycemic load diet prevents emergence of subclinical depression during weight loss. The question of whether dietary composition influences mood and cognition has been controversial because most previous studies have not provided food (through controlled diet), or have been conducted for only short periods of time. ARS Funded Researchers at Tufts University in Boston, MA assessed the effects of dietary glycemic load on mood and cognition in 39 adults undergoing a caloric restriction program for 1 year. During the first 6 months of the program, when all food was provided, a rise in subclinical symptoms of depression occurred in the subjects randomized to a high glycemic load diet versus no such change in the subjects randomized to a low glycemic load diet, indicating that consumption of a low glycemic load diet was protective against negative affect during weight loss. This study, due to its long-term provision of food of carefully controlled composition, provides the first evidence that dietary carbohydrate/fat balance in the diet can influence mood.
4. Heritability and the environment affect lipid risk factors for cardiovascular diseases. The heritability of lipid risk factors for cardiovascular disease is uncertain. ARS Funded-Researchers from Tufts University studied the heritability of lipid parameters in a rare population of adult identical twins reared apart, to examine heritability. We found significant heritability of all lipid parameters but also substantial environmental contribution to each parameter. These findings emphasize the importance of the environment in health risk factors for cardiovascular disease in adults.