Dietary intake, physical activity and changes in body composition: A 20-month prospective study of middle-age women

This study was conducted to determine the extent that dietary intake and physical activity account for changes in body composition over time. Secondary objectives were to ascertain the extent that other proposed determinants of obesity, parental weight status, blood insulin levels, and restrained eating, contribute to changes in body composition over time. A 20-month prospective design was used. Participants consisted of 220 premenopausal middle-age women. Assessments included body weight, body fat percentage assessed by Bod Pod, 7-day weighed diet record, physical activity assessed by accelerometery, blood insulin levels, restrained eating using the Dutch Eating Behavior Questionnaire, and parental weight status at age 40. All assessments were conducted at baseline and again 20 months later. Over the study period, there were significant changes in body fat percentage, body weight, energy intake, physical activity, insulin, and energy derived from protein. There were no significant changes in restrained eating or energy derived from carbohydrate or fat. Change in energy intake was, by far, the strongest independent predictor of changes in both body fat and weight over the study period. Those who lost body fat and weight tended to decrease their energy intake more than those who gained body fat or weight. Change in physical activity was also a significant independent predictor of changes in body fat and body weight. Those who lost body fat or weight tended to increase physical activity, while those who gained body fat or weight tended to decrease physical activity. Dietary fat intake was predictive of changes in body fat, but not body weight. Blood insulin levels, restrained eating, parental weight status, dietary carbohydrate, and dietary protein were not predictive of changes in body fat or body weight over the 20-month study period. Based on these results, it appears that increased risk of weight gain over a 20-month period is primarily a function of increased energy intake and reduced physical activity in middle-age women.