Diet, Exercise, Metabolism, and Obesity in Older Women

Overview

Reductions in fat oxidation and resting metabolic rate (RMR) are associated with normal aging and are accelerated with menopause. As a result, postmenopausal women have an increased risk of abdominal obesity and ultimately the metabolic complications that lead to the insulin resistance syndrome and its associated risks (hyperlipidemia, type 2 diabetes, and coronary heart disease). Thus, there is a need to determine the most successful treatment to reduce visceral obesity in postmenopausal women. The purpose of this study is to determine if dietary-induced weight loss alone and/or weight loss combined with exercise at low and high- intensities differentially affect the reduction in visceral adipose tissue in postmenopausal women with abdominal obesity.

Design Overview: This study's protocol will last approximately 18 months. Phase 1 involves recruitment and screening followed by baseline research testing (Phase 2). Next, subjects will be randomly assigned to one of three 5-month treatments (Phase 3): diet and high-intensity exercise, diet and low-intensity exercise, or diet only. In the Maintenance Phase, subjects will return for visits at 6 \& 12 months following the completion of their 5 month intervention. Interventions: All treatment groups will experience the same total weekly caloric deficit (-2800 kcal/wk), but will derive this deficit by different reductions in dietary intake and exercise energy expenditure. The weekly caloric deficit will be accomplished as follows: 1) the diet alone group will reduce dietary intake by \~2800 kcal/week (\~400 kcal/day); 2) both exercise groups will expend \~400 kcal/wk in exercise energy expenditure and will reduce dietary intake by \~2400 kcal/wk (\~340 kcal/day) to achieve the 2800 kcal/wk deficit. The exercise will take place in an exercise facility at the Geriatric Research Center on the campus of the Wake Forest University/Baptist Medical Center. Two study personnel, including at least one trained technician, will supervise all exercise sessions. Emergency equipment will be kept on site during exercise sessions. Blood pressure and heart rate will be measured and recorded before each exercise session and participants will warm-up by walking for 3-5 min at a slow pace. Women will use the treadmill to exercise at an intensity of 45-50% (low-intensity AEX) or 70-75% (high-intensity AEX) of VO2max. Both groups will exercise 3 d/wk and duration of exercise will progress from 10-15 min the 1st week to 55 min by the end of the 6th week and thereafter for the low-intensity AEX group. The duration of exercise for the high-intensity AEX group will progress from 10-15 min the 1st week to 30 min by the end of the 6th week and thereafter. Injuries are minimized by a feasible progression of exercise duration as well as careful monitoring of proper footwear and stretching exercises. The diet intervention will consist of monthly meetings with a registered dietitian along with consuming a hypocaloric diet provided by the GCRC metabolic kitchen. Subjects will be asked to pick up their food three times a week. Two meals per day will be provided. In addition, a calcium supplement (1000mg) will be provided. Subjects will be required to keep a diary of other foods consumed including the calcium supplement. The diets will be composed of 50-60% carbohydrate, 15-20% protein, and 25-30% fat with adequate amounts of essential nutrients. The number of calories given to each subject will be estimated from energy expenditure estimates in combination with an activity factor. The diet only group will be provided with an approximate 400 kcal/day energy deficit diet, while both exercise groups will be provided with an approximate 340 kcal/day energy deficit diet. Menus and specific food choices will be determined by GCRC dietitians in consultation with each research subject.