You’ve probably heard that muscle burns fat once or twice from your favorite fitness Instagrammers, a bodybuilder in the gym, or maybe even a random Reddit user. But if you’re like us, you like to do your own research and find proof to back up or refute claims like this. Because we want to be strong and also know how our body works, specifically how it burns fat and builds muscle, we asked an expert.
“It’s not necessarily [that] muscle burns fat,” Rondel King, MS, CSCS, an exercise physiologist at NYU Langone’s Sports Performance Center told POPSUGAR. OK, so what actually burns fat? The first thing to know is that “The primary fuel source for muscle is glucose or glycogen,” which is the stored form of carbohydrates in the muscle, Rondel explained.
In order for your body to utilize fat and burn it, Rondel said the body has to convert triglycerides, the main form of fat stored in your body, into glucose. This happens through a process called gluconeogenesis. According to Rondel, gluconeogenesis takes place when your body needs glucose and also when you do high-intensity exercise like sprinting and weightlifting.
To be completely clear, no, muscle doesn’t directly burn fat. Instead, the fat molecules have to be converted into glucose — then your muscle will be able to use it for fuel, aka burn it. Although muscle doesn’t burn fat, the more muscle mass you have, the higher your resting metabolic rate (the amount of calories your body needs to perform basic functions that keep you alive like breathing) becomes. This means you’ll be burning more calories, Rondel explained.
It’s a pretty complex process, but at the end of the day, remember these two things: muscle doesn’t directly burn fat and the more muscle you have, the more calories you’ll burn.