MCT derivatives produced by the interesterification process are referred to as structural lipids or structural TGs. Interesterification is a process by which LCFA, such as oleic acid, are introduced into the final product. In the case of MCT derivatives, the product created is a rearranged TG with both MCFA and LCFA, in the desired ratios, on the same glycerine molecule. The existence of physiological actions of structured lipids on body weight and composition is explored in this section.
Human studies have been conducted with a variety of structured lipids as demonstrated in Table 14.3. Matsuo et al. (2001) examined the effects of a liquid diet supplement containing structured lipid composed of 10% MCFA and 90% LCFA as compared with a liquid formula containing LCT in 13 healthy male volunteers. Although body weight increased non-significantly in both groups, the rates of variation in body fat percentage were lower in the structured lipid group than in the LCT group throughout the 12-week study. Despite this, in another 12-week study comparing LCT with a diet supplemented with 14 g of structured fat containing only 1.7 g MCFA, results showed decreases in body weight, including subcutaneous and visceral fat as measured by air displacement methods (Kasai et al., 2003). Similarly, Takeuchi et al. (2002) examined the effects of 20 g of structured lipid containing MCFA and LCFA versus the same quantity of soybean oil for 3 weeks in 6 young men. The rate of variation in body fat mass as measured by bioelectrical impedance was lower with the structured lipids than with soybean oil.
Secondly, oils rich in MCT lack essential fatty acids, which makes them inappropriate to consume as the sole source of fat in the diet. For this reason, the addition of essential fatty acids such as n-6 and n-3 long-chain polyunsaturated fatty acids (n-6 and n-3 LCPUFA) to a structured lipid may be beneficial. Beermann et al. (2003) hypothesized that MCT combined with n-3 LCPUFA would act synergistically to stimulate fatty acid oxidation, resulting in LCFA release from adipocytes and blood lipid clearance. Ten overweight volunteers consumed a high-fat hypoenergetic diet for 15 days, including a formula containing either LCFA or a combination of MCFA and n-3 LCPUFAs (Beermann et al., 2003). Both groups showed equivalent reductions in body weight and fat mass (Beermann et al., 2003). However, the study measured weight loss with a scale and body fat by impedance, neither of which can give the breakdown of regional changes in body composition. Nonetheless, longer-term studies with larger sample sizes should be considered to determine the exact benefits of MCT and n-3 LCPUFA on weight loss, body composition, and blood lipid parameters.
Structured lipids have recently been tested as agents to decrease body weight and body fat accumulation and to improve lipoprotein profile in human studies. Results of these studies suggest that the daily intake of structured lipids could result in a reduction in body weight and fat accumulation. However, the exact ratio of MCT to LCT and the components of structured lipids required for optimal effects on both body composition and blood lipids need further investigation.
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