The influence of dietary calcium on fat metabolism at rest and during exercise
Abstract
The overall purpose of the studies included in this dissertation was to investigate the mechanism of calcium-mediated weight loss at the whole body and cellular levels. A further objective was to apply these findings to an exercise model and study the ability of calcium to alter fat metabolism and to improve endurance exercise performance. The first study utilized indirect calorimetry to estimate energy expenditure and substrate oxidation in response to a low-calcium meal challenge before and after a 12-week calorie-restricted diet. The diet intervention was a 500 kcal energy restriction with either low calcium, high supplemental calcium, or high dairy calcium. No changes were found in energy expenditure, but the respiratory exchange ratio was significantly lower and fat oxidation significantly higher than baseline in the high supplemental calcium group in response to the low-calcium meal (P = 0.01). The mechanism for this effect on fat oxidation may involve the actions of 1,25(OH) 2D3 and parathyroid hormone (PTH) on the muscle cell in response to calcium intake. Therefore, in study two, fat oxidation was measured after 1,25(OH)2D3 or PTH treatment in C2C12 skeletal muscle cells. 1,25(OH)2D3 suppressed oxidation of 14 C-palmitate after 72 hour pre-treatment with 100 nM of the hormone (P = 0.03). PTH treatment did not suppress fat oxidation as compared to controls. The third study of this dissertation examined the relationship between calcium intake and fat oxidation during endurance exercise and the resulting effect on running performance in endurance trained female runners. Compared to the control diet, fat oxidation was not altered during a 90 minute run at 70% VO2 max following the dairy calcium meal. Likewise, time to complete a subsequent 10K time trial was not lower after the dairy load. No effect of habitual calcium diet was observed. In summary, the results of the studies included in this dissertation indicate that habitual high calcium intake may increase fat oxidation in women at rest, which may be due to the action of Vitamin D at the muscle cell. However, dairy calcium intake prior to exercise did not improve fat oxidation during exercise or running performance in this protocol.
Degree
Ph.D.
Advisors
Teegarden, Purdue University.
Subject Area
Nutrition|Sports medicine
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