Q: I’ve heard that a supplement called MCT is good for weight loss. What is it and does it work?
MCT stands for medium-chain triglycerides – a type of dietary fat. Unlike longer-chain triglycerides found in most foods, MCTs contain 10 or fewer linked carbon atoms (longer-chain fats generally contain 12 or more carbon atoms). Why is this significant? Well, the shorter-chain length and unique molecular structure allows MCTs to bypass the usual mechanisms by which the body stores fat. Rather than being packaged into chylomicrons for transport to fat cells, they are instead shuttled directly into the liver, where they can be rapidly utilized for fuel. Moreover, they can be taken up in mitochondria without the need for carnitine-assisted transport, facilitating their use as an energy source. The upshot is that the body prefers to utilize MCTs for short-term energy needs, instead of depositing them into fat cells.
Research consistently supports the efficacy of MCTs in the context of a weight-loss diet. Multiple studies have shown that MCTs result in less fat deposition when substituted for long-chain triglycerides (LCTs) on a calorie-for-calorie basis. This is apparently attributed to a greater thermic effect, where approximately 50 percent more calories are burned during digestion, compared with LCTs. MCTs also have been found to increase satiety, reducing the number of calories consumed and thus indirectly impacting fat loss. The combined effects of increased dietary thermogenesis and decreased food consumption reduces caloric uptake by more than 100 calories a day. While this might not seem like much on the surface, consider that over the course of a year it would result in an extra 10 pounds of fat loss without changing anything else in your diet or activity levels!
Understand, though, that MCTs aren’t a “fat burner” per se. In order to lose body fat, you need to substitute MCTs for other calories in your diet – otherwise you will actually gain weight from the increased caloric intake. A viable strategy is to use MCT in place of a portion of your dietary carbohydrate. The caveat here is that MCTs contain approximately 8 calories per gram, as opposed to carbs, which contain only 4 calories per gram. Thus, for every gram of MCTs consumed, you need to cut out 2 calories of carbs.
The biggest downside to MCTs is that they can be harsh on the digestive system, with upset stomachs and nausea routinely reported as side effects. To limit gastrointestinal distress and facilitate better assimilation, MCTs are best consumed with a food source. Moreover, intake should be restricted to around 30 grams a day, which seems to be the tolerable daily upper limit.