Effects of energy deficit on the neuroendocrine response to exercise
Energy restriction has a high failure rate as most overweight/obese individuals regain lost body fat. The failure rate may be related to the neuroendocrine response (e.g. decreased concentrations of leptin, insulin, peptide YY3-36, T4, T3, and increased concentrations of ghrelin, etc.) to energy deficit; which causes increased energy intake and reduced total daily energy expenditure (TDEE). The alternative to energy restriction is to maintain energy intake and increase energy expenditure (e.g. physical exercise) to induce an energy deficit. Because physical exercise increases TDEE, the neuroendocrine response to exercise-induced energy deficit may be different than energy restriction and may not promote regain of lost body fat. The impact of exercise-induced energy deficit on the neuroendocrine response to energy intake and TDEE has not been systematically studied however. In addition, upon initiation of an exercise training program women do not lose body fat, whereas men do lose body fat. The apparent sex difference may be related to the neuroendocrine response to exercise that promotes increased energy intake and reduced TDEE in women but not men. The purposes of this study are, 1) to determine the independent effects of exercise with and without energy replaced on the neuroendocrine response (concentrations of leptin, insulin, peptide YY3-36, ghrelin, T4, and T3), and 2) to determine whether sex differences exists in the neuroendocrine response to exercise with and without energy replacement. Concentrations of selected key neuroendocrine hormones will be measured in sixteen (8 M, 8 W) previously sedentary, overweight/obese individuals during a 1-day baseline period, 4 days of daily exercise (30% of TDEE) with exercise energy added to the baseline diet (energy balance) and 4 days of daily exercise without exercise energy not added to the baseline diet (energy deficit). Results from this study will allow us to gain a better understanding how exercise impacts neuroendocrine regulation of energy balance in men and women. Exercise may promote continued body fat loss and be a better alternative to energy restriction.