Academic journal article Research Quarterly for Exercise and Sport

The Energy Balance Study: The Design and Baseline Results for a Longitudinal Study of Energy Balance

Academic journal article Research Quarterly for Exercise and Sport

The Energy Balance Study: The Design and Baseline Results for a Longitudinal Study of Energy Balance

Article excerpt

Purpose: The Energy Balance Study (EBS) was a comprehensive study designed to determine over a period of 12 months the associations of caloric intake and energy expenditure on changes in body weight and composition in a population of healthy men and women. Method: EBS recruited men and women aged 21 to 35 years with a body mass index between 20 and 35kg/[m.sup.2]. Measurements of energy intake and multiple objective measures of energy expenditure, as well as other physiological, anthropomorphic and psychosocial measurements, were made quarterly. Resting metabolic rate and blood chemistry were measured at baseline, 6 and 12 months. Results: Four hundred and thirty (218 women and 212 men) completed all baseline measurements. There were statistically significant differences by sex uncovered for most anthropomorphic, physiological and behavioral variables. Only percent of kcals from fat and alcohol intake, as well as energy expenditure in light activity and very vigorous activity were not different. Self-reported weight change (mean [+ or -] SD) over the previous year were 0.92 [+ or -] 5.24kg for women and--1.32 [+ or -] 6.1 kg for men. Resting metabolic rate averages by sex were 2.88 [+ or -] 0.35 ml/kg/min for women and 3.05 [+ or -] 0.33 ml/kg/min for men. Conclusion: Results from EBS will inform our understanding of the impact of energy balance components as they relate to changes in body weight and composition. Initial findings suggest a satisfactory distribution of weight change to allow for robust statistical analyses. Resting metabolic rates well below the standard estimate suggest that the evaluation of the components of total energy expenditure will be impactful for our understanding of the roles of energy intake and expenditure on changes in energy utilization and storage.

Keywords: body weight, obesity, physical activity, resting metabolic rate

Two thirds of the US population fall into the body mass index (BMI) categories of overweight or obese (Flegal, Carroll, Kit, & Ogden, 2012). Numerous studies demonstrate a relationship between body weight and chronic diseases including cardiovascular disease, metabolic disorders including diabetes, and some cancers (Haslam & James, 2005). As a result of these findings, reductions in weight and body fat have been a primary aim of national efforts to enhance the nation's health in such policy documents as Healthy People 2020 (2013). Recommendations on achieving a reduction in body fat are varied, but the typical strategy has focused primarily on restricting caloric intake, with occasional advice to increase energy expenditure (Swinburn, Sacks, & Ravussin, 2009).

Development of a theoretical framework to explain weight change and obesity has been a goal of numerous research groups for decades. The dominant framework is currently based on the concept of energy balance, which was derived from the laws of thermodynamics--that energy can be converted among forms but must be conserved. Specifically as related to body weight, an imbalance between energy consumption and expenditure will result in weight change. An imbalance from excessive consumption of energy will result in weight gain while excessive expenditure results in weight loss. The concept of "excessive" is generally thought to be defined by the relationship of intake and expenditure rather than to any particular range or threshold of kcals over time. Further, a change in the relationship of intake and expenditure is extrapolated, incorrectly, to a change in body fat rather than body mass.

However, body weight regulation is a complex collection of physiologic, metabolic, environmental, behavioral, and genetic variables that control energy intake and expenditure, as well as the rate and location of energy storage (Hill, Wyatt, & Peters, 2012; Spiegelman & Flier, 2001). In addition, altering energy intake or levels of expenditure usually results in some level of reciprocal compensatory change, with the physiological regulation of weight biased towards maintaining caloric intake and protecting energy stores (Hill et al. …

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