Carnitine supplementation fails to maximize fat mass loss induced by endurance training in rats

Background/Aims: Carnitine is a co-factor of the enzymatic system involved in long chain fatty acid transport across the mitochondrial membrane. This physiological role of carnitine raised the hypothesis that this compound could act as a 'fat burner' by optimizing fat oxidation and consequently reducing its availability for storage. Our aim was to verify whether carnitine supplementation could maximize fat mass loss in trained rats. Methods: Male Wistar rats (200 g) were divided into four groups: control (C), sedentary supplemented ( S), trained (T) and trained supplemented (TS). The training protocol consisted of bouts of swimming exercise (60 min.day(-1)) for 6 weeks. During the last 14 days, before sacrifice, the supplemented groups received a daily dose of 28 mg.kg(-1) of L-carnitine. Carcass fat content, weight and fat content of adipose tissues were evaluated in all experimental groups. Results: Our results indicate that carnitine feeding, per se, failed to promote fat mass loss. Endurance training successfully induced a decrease in the fat content in the carcass (28%) and the weight of adipose tissues (retroperitoneal and mesenteric depots by 41 and 20%, respectively) in comparison to C. Despite the augmented carnitine content in the soleus mitochondria (2-fold) observed in TS, the higher content did not maximize the fat loss induced by endurance training. Conclusions: Our data strongly suggest that endurance training, rather than carnitine content, is the major factor involved in fat mass loss. Copyright (C) 2004 S. Karger AG, Basel.