Animal and human studies indicate enhanced EE and satiety after MCT consumption; these studies were conducted to determine if these characteristics translate into decreases in fat mass. In animals consuming MCT, body weight was lower, fat depots smaller (Lavau and Hashim, 1978; Bray et al., 1980; Baba et al., 1982; Geliebter et al., 1983; Crozier et al., 1987; Hill et al., 1993), and adipose size reduced (Baba et al., 1982; Crozier et al., 1987) with MCT compared with LCT. These experiments suggest that the decreased deposition of fat in the MCT-fed rats may have resulted from obligatory oxidation of MCT-derived fatty acids in the liver after being transported there via the portal vein, leaving almost no MCT derivatives for incorporation into body fat. Overall, these animal studies with MCT indicate positive results relating to body weight, suggesting a potential for dietary prevention of human obesity via MCT intake.
Diets high in fat have been previously shown to induce a gain in body weight. However, substitution of a readily metabolized fat for a less well metabolized fat, within the context of a very high fat, energy-dense diet, can potentially limit excess energy intake and resultant weight gain (Stubbs and Harbron, 1996). MCT have been shown to reduce body weight effectively in numerous studies (Binnert et al, 1998; Krotkiewski, 2001; Nosaka et al., 2003; St-Onge and Jones, 2003; St-Onge et al., 2003b). However, others have not found positive effects on body weight (Yost and Eckel, 1989; St-Onge et al., 2003a). A summary of studies on the effects of MCT on body weight and composition is provided in Table 14.3.
The addition of MCT to hypocaloric diets displays variable effects. Yost and Eckel (1989) compared MCT and LCT feedings during and after 4 or 12 weeks of hypocaloric feedings in 16 obese women. It was concluded that MCT are safe, but fail to increase the rate or amount of weight loss. However, a major drawback in this study was that the authors did not measure EE or body composition. Another study tested the effects of a very low calorie diet supplemented with MCT versus a low-fat, high-carbohydrate regimen over 4 weeks (Krotkiewski, 2001). The MCT group showed a significantly greater decrease in body weight during the first 2 weeks compared with the group consuming the low-fat, high-carbohydrate diet. The contribution of body fat to the total weight loss was also higher while the contribution of fat-free mass was lower, as measured by dual-energy x-ray absorptiometry. Similarly, Nosaka et al. (2003) randomized 73 subjects into two groups and provided them with 2100-2400 kcal/day of energy, including 5 g/day of MCT or LCT. After 12 weeks, subjects on the MCT diet demonstrated decreases in total body fat, subcutaneous fat, and visceral fat as measured by the air-displacement method. The authors suggested that a PP increase in thermogenesis was the cause of the weight loss, but EE was not measured. Overall, the benefits of MCT supplementation in combination with a hypocaloric diet are significant; however, future studies are needed to confirm these results.
St-Onge et al. (2003a) recruited 17 obese women to assess body composition by magnetic resonance imaging (MRI) after long-term consumption of an MCT-supplemented diet. Changes in total and subcutaneous adipose tissue volumes were not significantly different between MCT and LCT diets. The authors hypothesized that the lack of effect on body composition in women may have been due to inadequate intake of MCT oil, and thus a smaller increase in EE. Therefore, the same investigators recruited 19 healthy, overweight men who consumed diets rich in MCT or LCT (St-Onge and Jones, 2003; St-Onge et al., 2003b). This study found a greater decrease in body weight, including the upper body adipose tissue as measured by
Table 14.3 Human work on the chronic effect of MCT and structured lipids on body weight and composition
Study diet including amount of MCT
Outcomes on body weight and body composition
St-Onge and Jones, 2003; St-Onge et al., 2003b
Randomized, cross-over study Controlled diet 24 overweight men
St-Onge et al., 2003a
Randomized, cross-over study Controlled diet 17 overweight women
Beermann et al., 2003
Randomized, cross-over study Controlled diet 10 healthy overweight men
Yost and Eckel, 1989
40% fat of total energy (75% from experimental oil) as functional oil composed of ~ 64.7 g MCT* (64.7% of fat) + PS (22 mg/kg body weight) + n-3 fatty acids (5% of fat) versus ~100 g olive oil for 29 days
40% fat of total energy (75% from experimental oil) as functional oil composed of ~50 g MCT* (50% of fat) + PS (22 mg/kg body weight) + n-3 fatty acids (5 % of fat) versus ~100 g beef tallow for 27 days
1500 kcal diet with 55.5% as fat ~53 g MCT + 16 g n-3 LCPUFA/day versus LCT (vegetable oils) for 15 days
800 kcal/day liquid diet with 30% of calories as 6% of calories as LCT (5 g) and 24% as MCT (21 g) or LCT (27 g) for 4 or 12 weeks i BW and body mass i Total adipose tissue i Upper adipose tissue NSi subcutaneous adipose tissue i BW to same extent as beef tallow ^ Total adipose tissue ^ Subcutaneous adipose tissue
^ Body fat mass
^ BW to same rate as LCT ^ Serum ketones ^ N balance rx> d.
Table 14.3 Continued
Study diet including amount of MCT
Outcomes on body weight and body composition
OP i-l rci
Matsuo et al., 2001
Parallel arm study Ad libitum diet 13 healthy male volunteers
Tsuji et al., 2001
Parallel arm study Ad libitum diet 78 healthy men and women
Nosaka et al., 2003
Randomized, crossover study Ad libitum diet 73 healthy men and women
Takeuchi et al., 2002
Randomized, cross-over study Ad libitum diet 6 active young men
Kasai et al., 2003
Parallel arm study Ad libitum diet 82 subjects
Structured medium- and long-chain triglycerols composed of ~20 g medium- (10%) and ~180 g long-chain (90%) fatty acids versus LCT for 12 weeks
60 g total fat including 10 g MCT or 10 g LCT for 12 weeks
2100-2400 kcal diet including 65-73 g/ day of total fat with 5 g of MCT or 5 g of LCT (rapeseed and soybean oil) for 12 weeks
Structured lipids 20 g of dietary triglycerols containing (20%) medium- and (80%) long-chain fatty acids (TML) 4 g MCT versus 20 g/day of soybean oil for 3 weeks
Structured medium- and long-chain triglycerols (MLCT) diet consumed 14 g of MLCT containing 1.7 g MCFA versus LCT for 12 weeks
NS T BW to same extent as LCT T Body fat to same extent as LCT i Body fat variation i BW in both groups but T weight loss in MCT i Body fat mass in both groups but T in MCT in pt BMI > 23 i Subcutaneous adipose tissue in pt BMI > 23 i Visceral fat in pt BMI < 23
i Total adipose tissue i Subcutaneous adipose tissue i Visceral adipose tissue
NS T BW to same extent as soybean oil i Body fat i Rate of variation BW
^ Subcutaneous and visceral fat
Abbreviations: BW, body weight; BMI, body mass index; MCT, medium-chain triglycerides; MCFA, medium-chain fatty acids; LCT, long-chain triglycerides; LCPUFA, long-chain fatty acids; N, nitrogen; NS, non-significant; PS, plant sterol; pt, patients.
* Calculated based on 3000 kcal.
MRI, with MCT compared with LCT consumption; these results were probably due to the increase in measured EE and fat oxidation observed with MCT intake (St-Onge and Jones, 2003; St-Onge et al, 2003b). The authors concluded that substitution of MCT for LCT in a targeted energy-balanced diet might prevent long-term weight gain via increased EE. Furthermore, the results indicated that MCT may be a better tool in the prevention of weight gain when body weight is not yet highly elevated, since MCT consumption stimulated EE and fat oxidation to a lower extent in men of greater body weight compared with in men of lower body weight (St-Onge et al, 2003b).
These studies suggest that replacing LCT with MCT oil could produce body fat loss over long periods of time, with or without reduced energy intake. However, the exact area of fat loss in the human body is still undetermined. Individual and genetic differences in the populations studied, as well as varying methods of analysis for body composition, may make generalizations more difficult.
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