Exercise intensity does not affect depression of resting metabolic rate during severe diet restriction in male Sprague-Dawley rats.
This study examined the effects of high and low intensity exercise on the resting metabolic rate during severe dietary restriction. We hypothesized that exercise would attenuate and/or offset the decline in resting metabolic rate during energy-deficit conditions. Thirty-two male 90-d-old Sprague-Dawley rats were divided into four groups: control, diet restriction only, diet restriction plus high intensity exercise, and diet restriction plus low intensity exercise. The body weights of the diet-restricted groups were rapidly reduced over 5 wk until rats in these three groups weighted 64% of control weight, and this difference in body weight was maintained for the last 5 wk of the study. The high and low intensity exercise groups ran 5 d/wk at 75 and 37.5%, respectively, of maximal running speed for 45 and 90 min/d, respectively. Resting metabolic rate (23-h oxygen uptake) was measured during wk 2, 4, 6, 8 and 10. Resting metabolic rate for the three diet-restricted groups was significantly lower (25-37%) than for the controls for all measurements. Exercise training had no effect on the diet-induced depression of resting metabolic rate, with the diet-restricted groups differing among each other by < 2% during the measurement periods. During severe diet-restriction, exercise-induced elevations of resting metabolic rate seem to be greatly reduced or eliminated. This absence of an exercise effect on resting metabolic rate persisted through 5 wk of reduced body weight maintenance. We conclude that during severe diet restriction, exercise offers no "protective" or enhancing effect on resting metabolic rate.
Ballor
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Department of Human Development Studies, University of Vermont, Burlington 05405-0117.
Poehlman
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ET
D000818:Animals; D005215:Fasting / Q000378:metabolism*; D005502:Food; D008297:Male; D010101:Oxygen Consumption; D005082:Physical Exertion; D051381:Rats; D017207:Rats, Sprague-Dawley