A study in the journal Nature found a new hormone that is produced during muscle contractions that elevates fat burning and turns white fat into brown fat. Higher levels of this new hormone—called irisin—also improve metabolic health, even when on a high fat diet. You’re probably wondering why turning your white fat into brown fat would be a good thing. White fat makes up both subcutaneous fat that is right below the skin, and belly fat that is deep inside the body and surrounds the organs. Subcutaneous fat is inert and just sits around making you look fat. Visceral fat is metabolically active, producing substances called adipokines that increase blood pressure, create more fat, and decrease insulin sensitivity. Visceral fat is bad, bad, bad. In contrast, brown fat is not so bad because it is metabolically active in that it requires energy and burns calories. Its purpose is to generate heat and keep us warm and is found in larger proportions in children and babies.The recent study found that any time you perform muscle contractions the body produces the hormone irisin, and it goes straight to white fat cells and turns them into brown fat. The brown fat then contributes to faster metabolism and glucose tolerance, which can lead to fat loss. For example, in the study, researchers found that humans who did aerobic exercise had much higher levels of irisin at the end of the study than at baseline when they had been sedentary. But the researchers asked the question, why does aerobic exercise rarely produces significant fat loss? It may be that more powerful, intense muscle contractions are necessary for robust elevations in irisin that result in fat loss. Further, lifting weights builds muscle and elevates protein synthesis, which has a much greater effect on insulin health and overall metabolism.
For best body composition results do the following:
• Perform a periodized strength training program in which you use multi-joint lifts, always count tempo, and train a high volume. • Do regular physical activity throughout the day, such as frequent vigorous walks or body weight exercises if you have a desk job to repeatedly enhance insulin sensitivity. • Avoid being sedentary as much as possible because lack of movement, even if just for a few hours, lowers glucose tolerance, and fat burning.