Energy Balance and Weight Control (Male and Female): Considerations
Energy balance is a complex process influenced by numerous factors including sex, age, acute and chronic exercise, genetic factors, as well as metabolic-, stress-, and sex-related hormones. This chapter focuses on sex-related differences in weight control
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Energy Balance and Weight Control (Male and Female): Considerations Kristin Ondrak, PHD CONTENTS Introduction to Energy Balance Hormones Involved in Energy Balance, Fat Distribution, and Weight Control Influence of Physical Activity on Appetite and Energy Balance Effects of Exercise on Hormones: Sex Differences Summary References
INTRODUCTION TO ENERGY BALANCE Energy balance is a reflection of an individual’s energy intake vs. expenditure, and is manifested in their body mass. When intake is similar to expenditure, neutral energy balance occurs and body mass remains stable. However, when intake exceeds expenditure, positive energy balance occurs (also termed energy excess); the body stores the excess energy and body mass increases. The opposite results when expenditure exceeds intake, termed negative energy balance or energy deficit (30). It is important to keep in mind that intake and expenditure should be compared over the long term rather than for shorter time periods as it is nearly impossible to match them on a daily basis. When even small deficits or excesses in daily energy balance occur day after day, substantial changes in body mass can result. For example, the addition of daily sugar-sweetened beverages to one’s diet resulted in substantial increases in body mass and increased risk for type II diabetes in a 4-year cohort analysis of women in the Nurse’s Health Study II (33). These researchers found that by increasing the consumption of sugar-sweetened beverages from less than one per week to one or more per day, these women consumed
From: Endocrinology of Physical Activity and Sport: Second Edition Edited by: N. Constantini and A.C. Hackney, DOI 10.1007/978-1-62703-314-5_10 © Springer Science+Business Media New York 2013 175
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an extra 358 kcal/day and gained ~4.5 kg on average (33). Thus, seemingly small additions to one’s daily diet can quickly add up to substantial changes in body mass and energy balance. An individual’s total daily energy expenditure is comprised of three main components: resting metabolic rate (60–75% of the total), diet-induced thermogenesis (10–15%), and activity thermogenesis, which can be further subdivided into exercise and non-exercise components (14). Resting metabolic rate (RMR) is closely related to the amount of fatfree mass (i.e., lean mass) and tends to be greater in men compared to women (29). These sex differences are attributable to the greater amount of fat-free mass in males vs. females, on average. Basal metabolic rate decreases with age, and research has shown that it is 4.6% lower in older participants, compared to younger (20). Lean mass is also related to diet-induced thermogenesis, such that greater amounts of lean mass are associated with more calories being burned following a meal. Finally, several other factors are related to diet-induced thermogenesis including age, sex, fitness level, and menstrual cycle phase. Some research has shown that body composition and physical activity levels were more closely related to energy expenditure (EE) than
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