The debate on the ideal diet to lose weight continues pending robust long term randomised controlled trials. The high fat diet, despite its illogical approach often results in astounding anecdotal reports of significant and rapid weight loss. Nutrients are handled differently by the intestines, with varying methods of transport in circulation and further differences in hepatic handling. Even the same nutrient as fat may be handled diversely depending on the type of fat ingested.Components of Dietary fat
It seems that the length of the fatty acid chains might influence the way triglycerides are handled. This could result in variations in absorption, metabolism and hence energy efficiency of medium chain (6-12 carbon atoms) vs. long chain (>12 carbon atoms) triglycerides. Studies in rats infused with MCT (medium chain triglycerides) and LCT (Long Chain Triglycerides) have shown that weight gain is lower by up to 75% in those given MCT. J Nutr. 1992 Jul;122(7):1483-92 Since total energy intake is similar, increased energy expenditure was likely to be an explanation. Studies in humans, often single meal studies, have demonstrated a higher post prandial thermogenesis on an MCT diet. A study involving lean and obese subjects who ate a single meal with 30% fat composition, either as LCT or MCT, resulted in a 48% higher energy expenditure in lean subjects on MCT as opposed to lean subjects on LCT at 6 hours. The obese subjects on MCT also showed a 65% higher energy expenditure than obese subjects who ate LCT. Am J Clin Nutr. 1991 May;53(5):1130-3. Another study with a slightly longer duration of assessment and varying concentrations of MCT (0-30 gms) confirmed similar benefits of MCT on energy expenditure facilitation which was sustained during the 24 hours of the study. The energy expenditure was proportional to the increase in MCT ratio in the diet. Eur J Clin Nutr. 1996 Mar;50(3):152-8. The benefits of MCT on energy expenditure has been shown to be sustained during a study duration of up to 7 days, Metabolism. 1989 Jul;38(7):641-8. but not at day 14. Am J Clin Nutr. 1999 May;69(5):883-9. This could be translated into daily practice in weight loss management as a need for cycling the use of MCT to sustain the energy expenditure produced. It has also been noted that women are less likely to respond with higher energy expenditure to an MCT diet compared to men, J Nutr. 2002 Mar;132(3):329-32. which could have explained the lack of effect maintenance at 14 days in the above mentioned study. While a choice of MCT over LCT could potentially facilitate short-term weight loss through increased energy expenditure, is the long-term issue really about keeping the total fat intake low rather than the type of fat? J Clin Invest. 1985 Sep;76(3):1019-24.
MCT diets seem to improve satiety with lower energy intakes in rodent Physiol Behav. 1992 Oct;52(4):815-7 and human studies. Int J Obes Relat Metab Disord.1996 Jul;20(7):651-60. While a hormonal explanation for the satiety promoting effect of MCT has been studied, contradictory results emerged with LCTs producing better satiety effects, associated with greater gastric distension following LCT!. MCT produced no GIP, Pancreatic Polypeptide, Neurotensin Gut. 2000 Jan;46(1):32-6. or CCK rise Gastroenterology. 1999 Jan;116(1):46-53. and a lower Peptide YY response than LCTs. Eur J Clin Invest. 1998 Feb;28(2):123-30.
An increased energy expenditure and increased satiety induced by MCT should translate into less fat depots and greater weight loss in the long term. Studies have shown lower fat depots with smaller adipocytes following MCT consumption as opposed to LCT use, Am J Clin Nutr. 1983 Jan;37(1):1-4 but weight loss facilitation with MCT has not yet been demonstrated. Am J Clin Nutr. 1989 Feb;49(2):326-30. A lack of weight loss has been observed despite increased satiety and decreased energy intake after MCT diets in humans. Int J Obes Relat Metab Disord. 1996 Jul;20(7):651-60. Thus while in theory an MCT diet should favour weight loss, long term data to prove that this is indeed the case is awaited.
It seems that the length of the fatty acid chains might influence the way triglycerides are handled. This could result in variations in absorption, metabolism and hence energy efficiency of medium chain (6-12 carbon atoms) vs. long chain (>12 carbon atoms) triglycerides. Studies in rats infused with MCT (medium chain triglycerides) and LCT (Long Chain Triglycerides) have shown that weight gain is lower by up to 75% in those given MCT. J Nutr. 1992 Jul;122(7):1483-92 Since total energy intake is similar, increased energy expenditure was likely to be an explanation. Studies in humans, often single meal studies, have demonstrated a higher post prandial thermogenesis on an MCT diet. A study involving lean and obese subjects who ate a single meal with 30% fat composition, either as LCT or MCT, resulted in a 48% higher energy expenditure in lean subjects on MCT as opposed to lean subjects on LCT at 6 hours. The obese subjects on MCT also showed a 65% higher energy expenditure than obese subjects who ate LCT. Am J Clin Nutr. 1991 May;53(5):1130-3. Another study with a slightly longer duration of assessment and varying concentrations of MCT (0-30 gms) confirmed similar benefits of MCT on energy expenditure facilitation which was sustained during the 24 hours of the study. The energy expenditure was proportional to the increase in MCT ratio in the diet. Eur J Clin Nutr. 1996 Mar;50(3):152-8. The benefits of MCT on energy expenditure has been shown to be sustained during a study duration of up to 7 days, Metabolism. 1989 Jul;38(7):641-8. but not at day 14. Am J Clin Nutr. 1999 May;69(5):883-9. This could be translated into daily practice in weight loss management as a need for cycling the use of MCT to sustain the energy expenditure produced. It has also been noted that women are less likely to respond with higher energy expenditure to an MCT diet compared to men, J Nutr. 2002 Mar;132(3):329-32. which could have explained the lack of effect maintenance at 14 days in the above mentioned study. While a choice of MCT over LCT could potentially facilitate short-term weight loss through increased energy expenditure, is the long-term issue really about keeping the total fat intake low rather than the type of fat? J Clin Invest. 1985 Sep;76(3):1019-24.
MCT diets seem to improve satiety with lower energy intakes in rodent Physiol Behav. 1992 Oct;52(4):815-7 and human studies. Int J Obes Relat Metab Disord.1996 Jul;20(7):651-60. While a hormonal explanation for the satiety promoting effect of MCT has been studied, contradictory results emerged with LCTs producing better satiety effects, associated with greater gastric distension following LCT!. MCT produced no GIP, Pancreatic Polypeptide, Neurotensin Gut. 2000 Jan;46(1):32-6. or CCK rise Gastroenterology. 1999 Jan;116(1):46-53. and a lower Peptide YY response than LCTs. Eur J Clin Invest. 1998 Feb;28(2):123-30.
An increased energy expenditure and increased satiety induced by MCT should translate into less fat depots and greater weight loss in the long term. Studies have shown lower fat depots with smaller adipocytes following MCT consumption as opposed to LCT use, Am J Clin Nutr. 1983 Jan;37(1):1-4 but weight loss facilitation with MCT has not yet been demonstrated. Am J Clin Nutr. 1989 Feb;49(2):326-30. A lack of weight loss has been observed despite increased satiety and decreased energy intake after MCT diets in humans. Int J Obes Relat Metab Disord. 1996 Jul;20(7):651-60. Thus while in theory an MCT diet should favour weight loss, long term data to prove that this is indeed the case is awaited.