L-Carnitine supplementation combined with aerobic training does not promote weight loss in moderately obese women

L-Carnitine (L-C) transports fatty acids into mitochondria for oxidation and is marketed as a weight loss supplement. In a double-blind investigation to test the weight loss efficacy of L-C, 36 moderately overweight premenopausal women were pair matched on Body Mass Index (BMI) and randomly assigned to two groups (N = 18). For 8 weeks the L-C group ingested 2 g twice daily of L-C, while the placebo (P) group ingested the same amount of lactose. All subjects walked for 30 min (60-70% maximum heart rate) 4 days/week. Body composition, resting energy expenditure (REE) and substrate utilization were estimated before and after treatment. For the subjects who completed the study (15 P, 13 L-C), no significant changes in mean total body mass (TBM), fat mass FM, and resting lipid utilization occurred over time, nor were there any significant differences between groups for any variable. Conversely REE increased significantly for all subjects, but no between group differences existed. Five of the L-C group experienced nausea or diarrhea and consequently did not complete the study. Eight weeks of L-C ingestion and walking did not significantly alter the TBM or FM of overweight women, thereby casting doubt on the efficacy of L-C supplementation for weight loss.

Short-term changes in body composition and metabolism with severe dieting and resistance exercise

The primary aim was to investigate whether the reduction in resting metabolic rate (RMR) and fat free mass (FFM) associated with a short-term very low kilojoule diet (VLKD) is altered by concurrent resistance exercise. Twenty overweight, premenopausal women were pair matched on body surface area and randomly assigned to either diet only (3,400 kJ/day) or diet combined with resistance training. Before and after 4 weeks of treatment, RMR was assessed by indirect calorimetry; total body mass (TBM), FFM, and fat mass (FM) by dual energy x-ray absorptiometry; total body water (TBW) by bioelectrical impedance; and strength by a weight-lifting test. Both groups had significantly lower TBM, FFM, FM, TBW, absolute RMR, and RMR, with FFM as the covariate, in the posttests than the pretests with no significant differences between groups. It was concluded that 4 weeks of resistance training did not prevent or reduce the decline in FFM and RMR observed with a VLKD.

Prevention of arousal-induced hyperlipidemia by glucose ingestion

Thirteen subjects were investigated to compare the effects of pre-event glucose (G) and placebo (P) ingestion on plasma free fatty acid (FFA) concentration during mental work. Subjects performed two trials of a videogame and received money for each point scored. Thirty minutes before commencing each trial, subjects ingested either a solution containing 50 g of G or an identically sweetened and colored placebo. Order of ingestion was partially counterbalanced. Heart rate, the measure of arousal monitored, increased significantly above baseline during each trial, but there was no difference in this rise between trials. The main finding from this experiment was that after ingesting glucose, subjects had a stable blood FFA concentration during the videogame, while after the ingestion of placebo subjects had a significantly higher blood FFA during videogames than they had at baseline. These data suggest that arousal-induced hyperlipidemia can be prevented by pre-event glucose ingestion.