Bulletproof coffee: the latest diet fad

Bulletproof Coffee is a drink that contains coffee, unsalted butter from grass-fed cattle (rich in omega-3 fatty acids) and medium-chain triglycerides (MCTs).

Medium-chain triglycerides are fats that, like all fats, provide a large amount of energy in a small volume, but are still quickly absorbed and metabolized in a similar way to carbohydrates. Medium-chain triglycerides may reduce body fat, improve the metabolism of carbohydrates and proteins, increase the absorption of essential elements such as calcium and potassium, and lower the risk of heart disease by reducing blood cholesterol and triglyceride levels.

There are claims that the Bulletproof line of beverages reduces hunger, improves mental focus and accelerates weight loss. These claims are questionable. The brain mainly uses carbohydrates as an energy source, so the high fat content of the drink will not support the brain's energy supply. Studies conducted on animals show that high-fat diets reduce mental function and promote memory loss. People use Bulletproof Coffee as a meal replacement. One cup provides more than 300 kcal, which would promote fat gain if people were eating a normal diet at the same time. Furthermore, MCTs only caused a small amount of weight loss. Fads come and go, so it will be interesting to see if Bulletproof Coffee will still be around in a year or two.

(Lipids in Health and Disease, 13: 194, 2014; The New York Times, December 14, 2014)