Medium-chain fatty acids (MCFA) have attracted attention as part of a healthy diet, because they are absorbed and transported directly into the liver via the portal vein, metabolized rapidly by β-oxidation, and increase diet-induced thermogenesis. Because medium-chain triacylglycerols (MCT) containing only MCFA has a few weak points as frying oils, we have developed medium- and long-chain triacylglycerols (MLCT). MLCT is produced by lipase-catalyzed enzymatic transesterification. Recently, long-term clinical trials have demonstrated that MLCT and MCT result in less body fat-deposition. MLCT oil (Trade name: Healthy Resseta) is safe and can be substitute for common edible vegetable oils. Healthy Resseta has been approved as FOSHU (Food for Specified Health Use), by the Ministry of Health, Labour and Welfare of Japan in December 2002 for use as a cooking oil with a suppressing effect on body fat accumulation. Healthy Resseta is widely sold in Japan. J. Med. Invest. 54: 385-388, August, 2007

We found previously that the ingestion of margarine containing medium-chain triacylglycerols (MCT) resulted in a significant increase in postprandial thermogenesis when compared with long-chain triacylglycerols (LCT). Diets that included margarine containing MCT and LCT were compared for 12 weeks in 73 subjects to investigate the effects on body weight, body fat, areas of subcutaneous and visceral fat, serum total cholesterols, triglycerides, lipoproteins, plasma glucose, serum insulin, total ketone bodies, and the activities of aspartate aminotransferase, alanine aminotransferase, and γ-glutamyltranspeptidase. We conducted a double-blind, controlled study and used blended rapeseed oil and soybean oil (LCT) as a comparison. Two groups ingested 2, 100−2, 400 kcal/day of energy, 65−73 g/day of total fat, and 14 g/day of test margarine (5 g/day of MCT or LCT). The subjects on the MCT diet demonstrated significant decreases in body fat weight (− 3.8 ± 2.4 kg vs − 2.4 ± 1.7 kg; MCT vs LCT, mean ± SD), subcutaneous fat (− 38.2 ± 29.9 cm2 vs − 22.6 ± 19.3 cm2), and visceral fat (− 12.2 ± 11.2 cm2 vs − 1.6 ± 12.8 cm2) after 12 weeks. There were no clinical differences in measured blood parameters. We suggest that the postprandial increase in thermogenesis and control of postprandial triglyceride levels may explain these results.

This study investigated the effects of a liquid meal containing medium- and long-chain triacylglycerols (MLCT) on diet-induced thermogenesis (DIT) and was conducted in double-blind cross-over manner. Twenty subjects participated in this examination. The subjects consumed the liquid meal, which was made with 14g of canola oil (LCT, long-chain triacylglycerols) or MLCT containing about 12% medium-chain fatty acids (MCFA). Oxygen consumption and carbon dioxide production were measured by indirect calorimetry. Resting energy expenditure (REE) was determined based on there parameters, applying the equation of Weir. Increase in DIT after ingesting the liquid meal with MLCT during 6h was significantly greater than with LCT (P<0.05). The results suggest that the substitution of MLCT for cooking oil is useful to control body weigh and fat in subjects.

The purpose of this study was to investigate the effect of 5-10g of medium- chain triacylglycerols (MCT) on diet-induced thermogenesis in healthy humans. The study compared diet-induced thermogenesis after ingestion of test foods containing MCT and long-chain triacylglycerols (LCT), using a double-blind, crossover design. Eight male and eight female subjects participated in study 1 and study 2, respectively. In both studies, the LCT was a blend of rapeseed oil and soybean oil. In study 1, the liquid meals contained 10g MCT (10M), a mixture of 5g MCT and 5g LCT (5M5L), and 10g LCT (10L). In study 2, the subjects were given a meal (sandwich and clear soup) with the mayonnaise or margarine containing 5g of MCT or LCT. Postprandial energy expenditure was measured by indirect calorimetry before and during the 6 h after ingestion of the test meals. Diet-induced thermogenesis was significantly greater after 5M5L and 10M ingestion as compared to 10L inges- tion. Ingestion of the mayonnaise or margarine containing 5g MCT caused significantly larger diet-induced thermogenesis as compared to that of LCT. These results suggest that, in healthy humans, the intake of 5-10g of MCT causes larger diet-induced thermogenesis than that of LCT, irrespective of the form of meal containing the MCT.

Medium-chain triacylglycerols (MCT) are known to hydrolyze readily and completely to fatty acids and to be metabolized more easily by β-oxidation than long-chain triacylglycerols (LCT). Therefore, we investigated the effect of 2 wk of ingestion of food containing a small amount (6 g) of MCT on energy metabolism during moderate-intensity exercise and high-intensity exercise in recreational athletes. For comparison, the subjects were administered food containing MCT or LCT for 14 d, and were instructed to perform cycle ergometer exercise at a workload corresponding to 60% peak O2 uptake (VO2) for 40 min followed by a workload corresponding to 80% peak VO2 until exhaustion. Blood lactate concentration, VO2, VCO2, and rating of perceived exertion (RPE) were measured at rest and during exercise. The exercise time to exhaustion at a workload corresponding to 80% peak VO2 was significantly (p<0.05) longer in the MCT trial (10.2±7.6 min; mean±SD) than in the LCT trial (5.8±3.3 min). Blood lactate concentration and RPE during exercise were significantly (p<0.05) lower after ingestion of MCT-containing food. Fat oxidation rate was higher and carbohydrate oxidation rate was lower during exercise in the MCT trial than in the LCT trial, but the differences were not significant. These results indicate that the ingestion of MCT-containing food may suppress utilization of carbohydrate for energy production because of increased utilization of fatty acids for generating energy. In conclusion, our data suggest that short-term ingestion of food containing a small amount of MCT suppresses the increase in blood lactate concentration and RPE during moderate-intensity exercise and extends the duration of subsequent high-intensity exercise, at levels higher than those achieved by ingestion of LCT-containing food.

Previous studies indicated that a medium-chain triacylglycerol (MCT) diet could inhibit body fat accumulation. It is also well established that exercise can reduce fat mass. However, the effects of a combination of MCT diet and exercise on reduction of fat mass have not been studied. Here we examined whether MCT diet and exercise intervention exert cooperative effects on body composition. Rats were assigned to 4 groups: 1. LCT diet, control (LCT-C); 2. MCT diet, control (MCT-C); 3. LCT diet, exercise (LCT-E); 4. MCT diet, exercise (MCT-E). After the 6-wk intervention, visceral fat mass was measured by CT scan and dissection, and energy expenditure was estimated for 24 h. The value of the visceral fat mass showed a significant correlation between CT scan and dissection (r=0.995, p<0.001). Visceral fat mass in the MCT-C group was lower than that in the LCT-C group. Furthermore, the fat-lowering effects were greater in the MCT-E group than that in either intervention alone. Thus significant effects of the MCT diet and exercise on the reduction of visceral fat mass were observed. Energy expenditure was significantly higher in the MCT-E group than in the other groups. Our present findings suggest that combined intervention of MCT diet and exercise has an additive effect on reduction of visceral and subcutaneous fat accumulation, and that this effect may be partially related to increased energy expenditure. However, future studies are necessary to define the relationship between energy expenditure and fat mass accumulation.