Covert manipulation of the ratio of medium- to long-chain triglycerides in isoenergetically dense diets: effect on food intake in ad libitum feeding men.

Objective: This study examined whether isoenergetic substitution of MCT for LCT in HF, HE diets (639 kJ/100 g) limits the excess energy intakes frequently observed on high-fat diets of high energy density (HF, HE).
Subjects: Six healthy male volunteers [mean age (SD) = 27.17 (4.17 y) mean weight = 63.33 (7.33 kg), mean height = 1.72 (0.05 m)].
Design: The subjects were each studied three times during 14 d throughout which they had ad libitum access to one of three covertly-manipulated diets, which were randomly assigned in a counter-balanced design. The fat, carbohydrate (CHO) and protein in each diet (as percent energy) were identical at 62:28:10, with 2 day maintenance (1.5 x BMR, MF) beforehand. The ratio of MCT to LCT was 1:2, 1:1 and 2:1 on the low-, (LMCT) medium- (MMCT) and high-MCT (HMCT) diets, respectively. Within each diet every item was of the same composition and offered as a 3 day rotating menu.
Results: Energy intakes were significantly lower on the HMCT diet [F (2,240) = 7.52; p < 0.001] giving mean values of 13.50, 13.67, and 12.43 MJ/d on the LMCT, MMCT and HMCT diets, respectively. Food intake followed a parallel trend. By day 14 body weight changes amounted to +0.45, +0.41 and -0.03 kg, respectively.
Conclusion: These data suggest that substitution of a readily metabolised fat for a less readily metabolised fat, in very high fat diets can limit the excess energy intakes and weight gain that is usually produced by HF, energy-dense diets.