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.
1. Restaurant-stated calorie contents are broadly accurate with notable exceptions. A study by ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, MA, compared laboratory measurements of calories for 269 food items with the stated calories on restaurant menus and websites. Researchers collected the samples randomly from national fast food restaurants and sit-down chain restaurants in Boston, Massachusetts, Indianapolis, Indiana and Little Rock, Arkansas. On average, the laboratory measurements were only ten calories higher than the restaurants’ stated calories, which broadly supports the wider provision of information on food calorie contents. However, 19% of tested foods contained at least 100 calories more or less than listed, suggesting stated calories for individual foods are often unreliable. The researchers also found that lower calorie food items purchased in sit-down restaurants tended to have more calories than listed. For example, an item purchased as 300 calories and therefore suitable for weight loss or prevention of weight gain typically contained 90 calories more than listed. This study provides important information for consumers on the reliability of information on the calorie content of restaurant foods, and identifies areas where restaurants may improve quality control to provide more accurate information on food energy contents.
2. Trial of Human Caloric Restriction is Feasible. Caloric restriction is the only intervention tested in animal models that reliably increases lifespan. ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, MA, are participating in the first multi-site randomized controlled trial of caloric restriction in humans and have published the methodology for conduct of the trial and the intervention. Based on enrollment of human participants in 3 experimental sites and high retention of those subjects through a 2-year study, research studies of human caloric restriction are clearly feasible and will lead to results determining whether caloric restriction has benefits for lifespan and metabolic aging in old age in humans. In collaboration with other scientists participating in the multi-site randomized controlled trial of human caloric restriction we have now reported that recommendations to restrict energy intake by 25% reliably leads to weight loss of 10-14% of body weight based on studies involving measuring changes in energy expenditure and body energy stores during a long-term trial when all food is provided. These results are of practical significance because they will help refine recommendations for dietary change to induce changes in body energy stores in obesity, and will allow clinical obesity personnel to help patients understand the significance of energy intake in weight control programs.