The long-distance triathlon event (Ironman) has a profound effect on the metabolism. Among the many hormones known to affect energy intake and expenditure the adipocyte-derived leptin (1) and the recently described gastric-hormone ghrelin (2) are of particular interest. Ghrelin exerts a stimulatory effect on appetite and fat accumulation whereas leptin exerts an opposite effect. Ghrelin might be a short-term regulated signal. A reduction in food intake or a high energy expenditure is hypothesized with a subsequent rise in ghrelin to ensure sufficient energy intake in humans. We studied the effects of an international Ironman Competition on several endocrine parameters which are involved both in the short-term and in the long-term regulation of energy intake and body weight. Methods We investigated 50 male and female athletes participating at the IRONMAN in Klagenfurt (Carinthia, Austria). In only 18 male athletes out of the whole study group all investigations were performed three times. Blood samples were taken 5 days before the event (A), one day after (B) and 24 days after (C) the competition and determined for leptin, ghrelin, insulin and IGF-BP3. At each time point, body composition was also measured (not shown). Results Leptin was significantly changed (repeated measures in time; p=0.04) but the change was of minor magnitude (mean and SD; A: 1.3 ± 1 ng/ml; B: 0.8 ± 0.5 ng/ml; C: 1.75 ± 1.5 ng/ml). (Fig. 1). The same decline was found for IGF-BP3 after the event (B) (p=0.0012) but values of IGF-BP3 remained fairly constant at this reduced level (A: 3.5 ± 0.7 mg/L B: 3 ± 0.8 mg/L; C: 3 ± 0.5 mg/L) (Fig. 2). Neither insulin (p=0.33) or ghrelin (p=0.13) were significantly altered over time. However, those athletes who showed the greatest reduction in leptin after the competition (B) had the highest leptin levels 24 days after (C) the event (r=0.54, p=0.01). Discussion These findings show that ghrelin is not affected by a high energy demand in male athletes. This could be due to the food intake on a regular basis during the competition because also insulin levels were not changed. Given the fall in leptin and values of leptin 24 days after the competition, it is to suggest that those athletes who had the highest energy-turnover (reflected by the downregulation of leptin) compensated for this by restoring their empty energy stores within three weeks. Whether the subtle alteration in leptin and the persistent lowered levels of IGF-BP3 indicate that the net energy turnover of the competition can not be adequately restored within three weeks remains to be elucidated.
© Copyright 2004 Book of Abstracts - 9th Annual Congress European College of Sport Science, July 3-6, 2004, Clermont-Ferrand, France. Published by Eigenverlag. All rights reserved.