Aside from the erroneous concept of spot reduction, nothing might make fitness professionals cringe more than the suggestion that you can turn fat into muscle. While diet and exercise are powerful tools for health and wellbeing, making this physiological leap is only possible with, say, sorcery or witchcraft.
Generally speaking, “one type of tissue cannot convert to another type of tissue, so you can’t turn fat into muscle or vice versa,” says Trevor Thieme, C.S.C.S., senior manager of fitness and nutrition content at Openfit.
End of story.
Yet, it’s almost unfair to blame anyone who’s ever held the misconception that they can turn fat into muscle. It’s an oversimplification of physical transformation that makes for a powerful marketing message, which likely explains its origins.
This theme of anatomical alchemy has prevailed in exercise and weight-loss advertising for decades. And dramatic before-and-after photos used to sell everything from diet pills to this year’s version of the Shake Weight convincingly illustrate soft layers of fat shrinking down into hard, chiseled muscles.
It’s no wonder that those just beginning their fitness journey (and even many seasoned gym-goers, for that matter) are a little confused. It’s time to correct the record.
What Really Happens When You “Turn Fat Into Muscle”
Debunking the fat-to-muscle myth starts with a basic understanding of fat and muscle as two completely different types of tissue.
“Muscle consists of fibrous proteins,” says Pete McCall, host of the All About Fitness podcast. When you crush a challenging workout, you cause microscopic damage to those muscle fibers that the body must then repair. But it doesn’t just repair the damage — it also remodels it to make it larger and stronger in anticipation of that same “stress” again in the near future. If you stop exercising, the reverse happens, says McCall, explaining that the muscle fibers atrophy in the absence of the stress that triggered them to grow.
Fat, on the other hand, is composed of free fatty acids (triglycerides), and functions much differently. “Fat provides energy — that is its primary role,” says McCall. “Excess calories in the diet are stored as free fatty acids in what’s called adipose tissue.” So, if you’re consuming more calories than you burn during the course of your daily activities, you’ll likely gain body fat.
Running at a calorie deficit? The body will begin to tap into those energy stores, leaving you with less body fat. “When the body breaks down fat to produce energy, what’s left over is carbon dioxide and water. The vast bulk (80 percent) of that is carbon dioxide, so most of the fat you burn is literally breathed out into the air,” says Thieme.
Why Do People Believe Fat Becomes Muscle?
While it’s impossible to turn fat into muscle, you can, with proper nutrition and consistent exercise, simultaneously lose fat and gain muscle. “When you strength-train, you build muscle, a process that requires a lot of energy, much of which comes from fat,” explains Thieme, explaining that much of that building occurs between workouts. “That’s why you thin out when you lift weights regularly.”
While the fat doesn’t turn into muscle, your body composition does change: Your lean (fat free) mass increases and your fat mass decreases.
How to Lose Fat and Gain Muscle
So what do you actually need to do to “turn fat into muscle?” Studies show that high-intensity interval training (HIIT) is likely the fastest and most efficient way to shrink your waistline, followed closely by strength training. “But you also have to establish a strong fitness baseline in order to perform HIIT safely and effectively,” says Thieme. “That’s why I often recommend people work up to it. If you’re just starting your weight loss journey, focus on strength training.”
While low-intensity steady state exercise (LISS), like a slow jog or gentle hike, is an excellent option for recovery days, it’s not an ideal workout choice for losing fat. “Steady state aerobic exercise isn’t all that effective for long term fat loss because it presents the body with an unchanging stimulus to which the body quickly adapts,” says Thieme. “When adaptation slows or stops, so does muscle growth and fat loss, because that’s what those things are — adaptations.”