When I came into this forum, one of the first dialogues I held was an argument with Kabuki over Muscle Milk. I've been too lazy to cite this passage from "Power Eating" (my primary nutritional reference), but I've got the downtime to do it tonight. This summary basically explains why both our positions on Muscle Milk have validity, but either must be understood to be properly applied to your diet. MEDIUM-CHAIN TRIGLYCERIDE OIL Processed mainly from coconut oil, medium-chain triglyceride oil (MCT oil) is a special type of dietary fat that was first formulated in the 1950's by the pharmaceutical industry for patients who had trouble digesting regular fats. Still used in medical settings, MCT oil is also a popular fitness supplement, marketed as a fat burner, muscle builder, and energy source. At the molecular level, MCT oil is structured quite differently from conventional fats such as butter, margarine, and vegetable oil. Conventional fats are made up of long chains, with 16 or more carbon atoms strung together, and are thus known as long-chain triglycerides (LCTs). Body fat is also an LCT. MCT oil, on the other hand, has a much shorter carbon chain of only 6 to 12 carbon atoms, which is why it is described as a medium-chain triglyceride. As a result of molecular difference, MCTs are digested, transported, and metabolized much more quickly than fatty acids from regular oils or fats, and thus have some interesting properties. To begin with, MCTs are burned in the body like carbohydrates. Unlike conventional fats, MCTs are not stored as body fat but are shuttled directly into the cells to be burned for energy. In fact, MCT oil is burned so quickly that its calories are turned into body heat- a process known as thermogenesis, which boosts the metabolic rate. The higher your metabolism, the more calories your body burns. Does that mean if you take MCT oil you can rev up your metabolism and therefore burn more fat? Researchers at the University of Rochester looked into this possibility. In an experiment involving seven healthy men at the UofR, they tested whether a single meal of MCTs would increase the metabolic rate more than an LCT meal would. The men ate test meals containing 48 grams of MCT oil or 45 grams of corn oil, given in random order on separate days. In the study, metabolic rate increased 12 percent over six hours after the men ate the MCT meals but increased only 4 percent after LCTs were consumed. What's more, concentrations of triglycerides in plasma (the liquid portion of blood) were elevated 68 percent after the LCT meal, but did not change after the MCT meal. These findings led researchers to speculate that replacing the LCTs with MCTs over a long period of time might be beneficial in weight loss. Other researchers aren't so sure. In a study at Calgary Univeristy in Albert, Canada, healthy adults were placed on a low-carbohydrate diet supplemented with MCT oil. The researchers found that the diet had no real effect on elevating the metabolism. The calories burned over a 24-hour period were less than 1 percent of total caloric intake. However, there was a decrease in muscle protein burned for energy. Although MCT might not be a fat burner per se, it may help preserve lean mass by inhibiting its breakdown. In most studies on MCT oil and fat burning, volunteers ingest huge amounts of fat-- usually 30 grams or more-- to bring on metabolic-boosting results. Such amounts are just not tolerable for most people, because too much MCT oil produces intestinal discomfort and diarrhea. In my opinion, taking such huge doses of MCT oil to spurn fat burning just isn't practical. There's another problem with using MCT oil to try to burn fat. The recommended way to take MCT oil is with carbohydrates, a practice that prevents ketosis. In ketosis, by-products of fat metaoblism called ketones build up if carbs aren't available to assist in the final stages of fat breakdown. But when MCTs are taken with carbs, there is no effect on fat-burning whatsoever. Here's why: Carbs trigger the release of insulin, which inhibits the mobilization of fat for energy. Thus, there's simply no benefit to the use of MCT oil as a fat-burner. You have to do it the old-fashioned way, by exercising and watching your diet. Another claim attached to MCT oil is that it helps you put on muscle. But there are no controlled studies to prove this. Using some MCT oil to sneak in extra calories for harder workouts makes sense, though. Go east at first by taking one-half tablespoon to one tablespoon a day. Its fast absorption can cause cramping and diarrhea if you eat too much. Before experimenting with MCT oil, get your doctor's okay.