In obese subjects, insulin resistance and hyperinsulinemia are strongly associated with ATGL and HSL mRNA and protein expression, independent of fat mass. Data on weight reduction indicated that also other factors (e.g. leptin) relate to ATGL and HSL protein expression.

Endurance training has been shown to increase fat oxidation both at rest and during exercise. However, most exercise training studies have been performed at high exercise intensity in well-trained athletes, and not much is known about the effect of a low-intensity training program on fat oxidation capacity in lean sedentary humans. Here, we examine the effect of 3-month lowintensity training program on total and intramuscular triglyceride (IMTG)-and/or VLDL-derived fat oxidation capacity and skeletal muscle mRNA expression. Six healthy untrained subjects (aged 43 ؎ 2 years, BMI 22.7 ؎ 1.1 kg/m 2 , VO 2max 3.2 ؎ 0.2 l/min) participated in a supervised 12-week training program at 40% VO 2max three times weekly. Total and plasma-derived fatty acid oxidation at rest and during 1 h exercise was measured using [13 C]palmitate, and in a separate test, [ 13 C]acetate recovery was determined. Muscle biopsies were taken after an overnight fast. Total fat oxidation during exercise increased from 1,241 ؎ 93 to 1,591 ؎ 130 mol/min (P ‫؍‬ 0.06), and IMTG-and/or VLDL-derived fatty acid oxidation increased from 236 ؎ 84 to 639 ؎ 172 mol/min (P ‫؍‬ 0.09). Acetyl-CoA carboxylase-2 mRNA expression was significantly decreased after training (P ‫؍‬ 0.005), whereas lipoprotein lipase mRNA expression tended to increase (P ‫؍‬ 0.07). In conclusion, a minimal amount of physical activity tends to increase fat oxidation and leads to marked changes in the expression of genes encoding for key enzymes in fat metabolism. Diabetes 51:2220 -2226, 2002

Resistance exercise has recently been shown to improve whole-body insulin sensitivity in healthy males. Whether this is accompanied by an exercise-induced decline in skeletal muscle glycogen and/or lipid content remains to be established. In the present study, we determined fibre-type-specific changes in skeletal muscle substrate content following a single resistance exercise session. After an overnight fast, eight untrained healthy lean males participated in a approximately 45 min resistance exercise session. Muscle biopsies were collected before, following cessation of exercise, and after 30 and 120 min of post-exercise recovery. Subjects remained fasted throughout the test. Conventional light and (immuno)fluorescence microscopy were applied to assess fibre-type-specific changes in intramyocellular triacylglycerol (IMTG) and glycogen content. A significant 27+/-7% net decline in IMTG content was observed in the type I muscle fibres (P<0.05), with no net changes in the type IIa and IIx fibres. Muscle glycogen content decreased with 23+/-6, 40+/-7 and 44+/-7% in the type I, IIa and IIx muscle fibres, respectively (P<0.05). Fibre-type-specific changes in intramyocellular lipid and/or glycogen content correlated well with muscle fibre-type oxidative capacity. During post-exercise recovery, type I muscle fibre lipid content returned to pre-exercise levels within 120 min. No changes in muscle glycogen content were observed during recovery. We conclude that intramyocellular lipid and glycogen stores are readily used during resistance exercise and this is likely associated with the reported increase in whole-body insulin sensitivity following resistance exercise.

Context:In various observational studies, an inverse relation between calcium intake and body weight has been observed. A possible explanation could be an increased calcium excretion through the faeces caused by an increased dietary calcium intake. Objective: To examine whether an increased calcium intake could lead to changes in faecal fat and energy excretion. Design: Four different isocaloric diets with various calcium contents (400, 1200 and 2500 mg from dairy and 1200 mg from calcium carbonate (1200S)) were administered in a crossover design for 7 days each. Subjects: Five healthy men and five healthy women (age ¼ 2872, body mass index ¼ 24.170.4, body fat% ¼ 25.672.4) were recruited by local announcement. Measurements: At the end of every intervention period, faecal samples were collected for determination of fat, energy and calcium content, blood samples were obtained for determination of relevant blood parameters; and fat samples were obtained for measurement of the mRNA expression. Furthermore, resting energy expenditure and fat oxidation were measured with the ventilated-hood technique. Results: We observed a non-significant 56% increase in fat excretion (P ¼ 0.159) on the 2500 mg diet, compared to the 400 mg diet. The 2500 mg diet significantly reduced the expression of fatty acid synthase (FAS) mRNA (Po0.05) and the calcium content of the diets significantly affected calcium excretion. Furthermore, we saw a significant decrease of serum triglycerides on the 1200S diet (Po0.05). Conclusion: In this study, we observed a trend towards a higher fat excretion on the high-calcium diet, but this difference failed to reach statistical significance. It is possible that the relatively high protein content of the experimental diets increased calcium absorption from the intestine, thus decreasing the amount of calcium available for binding to fat and eliminating possible effects of dietary calcium on fat excretion. Furthermore, we observed decreases in FAS mRNA expression and serum triglycerides as a result of a high calcium intake.

The aim of the present study was to determine whether a single session of resistance exercise improves whole-body insulin sensitivity in healthy men for up to 24 h. Twelve male subjects (23 +/- 1 years) were studied over a period of 4 days during which they consumed a standardized diet, providing 0.16 +/- 0.01 MJ.kg(-1).day(-1) containing 15 +/- 0.1 energy% (En%) protein, 29 +/ -0.1 En% fat and 55 +/- 0.3 En% carbohydrate. Insulin sensitivity was determined 24 h before and 24 h after a single resistance exercise session (8 sets of 10 repetitions at 75% of 1 repetition maximum for two leg exercise tasks) using an intravenous insulin tolerance test. Insulin sensitivity index was calculated by the decline in arterial blood glucose concentration following intravenous administration of a single bolus of human insulin (0.075 IU.kg(-1) fat free mass). Basal glucose and insulin concentrations were not changed up to 24 h after the resistance exercise. However, a substantial 13+/-5% improvement in whole-body insulin sensitivity was observed, 24 h after the resistance exercise (P < 0.05). This study shows that even a single session of resistance exercise improves whole-body insulin sensitivity for up to 24 h in healthy men, which is consistent with earlier observations following endurance exercise tasks.