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What are MCTs?

Medium chain triglycerides appear to boost metabolism, suppress appetite, and reduce fat stores. Can MCTs help you lose weight?

By
Monica Reinagel, MS, LD/N, CNS,
August 22, 2012
Episode #201

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Several Nutrition Diva fans have asked me to dedicate an episode to MCTs, or medium chain triglycerides. MCTs have long been used as a nutrition therapy for certain medical conditions, but lately there’s been a lot of interest in MCTs as a weight loss supplement. Before you start popping pills, let’s take a look at the research.

What Are MCTs?

Triglyceride is just a fancy word for fat, and fat molecules come in a variety of sizes, or chain lengths. Most dietary fats (and virtually all unsaturated fats) are long chain triglycerides, with more than 12 carbon atoms in their molecular skeleton. But some saturated fats are shorter. Fats with 6 to 10 carbon atoms in their skeleton are referred to as medium chain triglycerides, or MCTs. Fats with fewer than 6 carbon atoms are short chain triglycerides.

What Do MCTs Do?

Because of their shorter chain length, MCTs sort of jump to the head of the line and are absorbed and metabolized more quickly than longer chain fats. They’re frequently used in medical nutrition formulas for people who, for whatever reason, can’t digest and absorb fats. They’re also added to baby formula to make it more closely resemble human breast milk.

Beyond these medical uses, research suggests that MCTs have special properties—like increasing metabolism or reducing appetite—that could make them a powerful tool in the fight against obesity. But before we get too excited, let’s take a closer look at the details.

MCTs increase metabolism. Studies ofboth animals and humans show that increasing the amount of MCT in the diet causes the body to burn more energy, or calories. The effect seems to be more pronounced in people who are overweight, which is certainly helpful. On the other hand, women seem to get far less of a metabolic boost from MCTs than men, which just seems sort of unfair. Either way, however, the effect seems to wear off after a couple of weeks, which makes it of somewhat limited usefulness as a tool for long-term weight management.

MCTs decrease food consumption. Studies in rats show that when you load them up with MCTs, they eat less and gain less weight. So far, so good. Studies in humans have been less encouraging. At least one study found that people ate less when fed a diet high in MCTs, but these folks were being fed a high-calorie, high-fat diet—with 2/3 of the calories coming from fat. The study diet was deliberately designed to result in weight gain—not the sort of thing we want to replicate in the real world. Moreover, a more recent study using a less extreme diet found that subbing in MCTs for longer chain fatty acids made no difference whatsoever in how much the subjects ate, either at that meal or the next one.

MCTs reduce fat stores. There’s one more tantalizing piece of evidence to consider. Some early studies have found that lab rats that were fed MCTs instead of longer chain fats ended up with smaller fat cells and fewer of them. That certainly sounds good. Unfortunately, a more recent study failed to duplicate that result. Interestingly, in the later study, diets high in fish oil were more effective than diets high in MCT in reducing fat stores. 

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