Metabolic Burner Types—Key For Healthy Weight Loss Or Pseudoscience?

person cooking food in bright kitchen


I first heard of “metabolic burner types” a few years ago when I overheard a trainer at my gym talking to a client about her weight loss goals. He was explaining that she was a “sugar burner” and more likely to store fat if she fed her body carbohydrates. As someone who has always wanted to look and feel my best, I remember looking it up on my phone as I walked back to the subway after my workout. But, once I lost service underground, I forgot all about it.

When I heard the term crop up again last week, my ears perked up. Like a moth to a flame, I’m always keen to learn any tips or tricks for revving up my metabolism in a healthy way. After all, a faster metabolism means I can eat more calories without gaining weight. And, as someone who thinks about what I’m going to make for dinner before I’ve even had breakfast, the foodie in me rejoices at this notion.

The sheer onslaught of nutrition advice and diets cropping up every year tells me that I’m probably not alone in interest in boosting my metabolism. But, how do we tease out scientifically sound recommendations from the scams? How do we know that the choices we’re making about what we eat and how we exercise are effective for our goals, and, more importantly, safe for our bodies? It’s not easy. Luckily, we turned to a registered dietician who has the education, training, and experience to help us make sense of “metabolic burner types.”

So, read on to learn if you should pay heed to “metabolic burner types” and her best advice on how to optimize your metabolism for better health and performance.

Meet the Expert

Tori Mincemeyer is a registered dietitian and nutrition coach who provides 1:1 nutrition counseling at her business, Living Nutrition.

What Is a "Metabolic Burner Type?"

In a nutshell, the theory of “metabolic burner types” arose as an explanation for different body shapes and tendencies, and the likelihood of storing or burning fat based on what you eat. “A ‘sugar burner,’ in theory, would run off of carbohydrates—a quicker, shorter-lasting source of energy—while a ‘fat burner’ would run off of fat for fuel—a longer-lasting, more sustainable energy source,” says Mincemeyer. Some iterations of the theory also include “muscle burners,” who tend to burn through protein more readily and have a “skinny fat” look, meaning that their figure may be slender, but with little to no muscle tone or definition.

Aim for at least 20 grams of protein per meal to help you maintain healthy muscle mass.

”Metabolic Burner Type:” Valid or Pseudoscience?

“Like many trends or diets, this description vastly oversimplifies how our body's metabolism works,” warns Mincemeyer. “In reality, our body is always utilizing a mixture of carbohydrates, fat, and a little protein as a fuel source. Depending on what our body ‘demands’ at any given time (for example, sitting at a desk vs. engaging in a HIIT workout), this utilization of fuel sources may shift.” In other words, it’s primarily the activity you’re engaging in that determines what specific ratio of fuels you’re burning, not some sort of inherent “type” of metabolism you do or don’t have. “Resting at our desk, our body will primarily be using fat as its main fuel source (again, a more sustainable, ‘slow burn’). When we sprint, jump, or do a HIIT workout, our body needs a quicker source of energy: carbohydrates,” explains Mincemeyer. “To say someone is a ‘sugar burner’ or a ‘fat burner’ fails to recognize how adaptable our body is, given the situation.” With that said, Mincemeyer notes that some people may be more efficient at using carbohydrates or fat, depending on the muscle fiber type that constitutes the majority of their muscle mass.

What Are Muscle Fiber Types?

person in running position


Mincemeyer explains that there are two primary types of muscle fibers in our body. “The characteristics vary in how quickly each fiber type fatigues and what type of fuel is primarily utilized (fats or carbohydrates),” she says. Type I fibers are called “slow-twitch,” and types IIa and IIx fibers are called “fast-twitch.” Slow-twitch fibers, which are the primary type recruited for activities like walking and jogging, are your endurance fibers. They don’t fatigue easily, and they mainly use fat as a fuel source. Fast-twitch fibers, which are recruited during sprinting, jumping, or other high-intensity activities, fatigue easily and rely primarily on carbohydrates to fuel their activity.

How Does Muscle Fiber Type Affect Metabolism?

Depending on your particular makeup, your body may rely more heavily on a certain fuel source, particularly during exercise. Genetics plays a role in determining your particular ratio. “Some people are born with a higher ratio of one or the other. Usain Bolt is a great example of someone who would be fast-twitch dominant,” says Mincemeyer. “Add extensive training onto someone who is genetically predisposed to one fiber type or another, and you have a world-class athlete.” 

But, you don’t have to be in contention for the next gold medal to use knowledge of muscle fiber types to optimize your fitness, fueling strategy during exercise, and metabolism. “The only way to know for sure what your ‘makeup’ is would be to have a muscle biopsy, which is pretty invasive,” notes Mincemeyer. “Most individuals are about a 50/50 mix of slow- vs. fast-twitch muscle fibers, but you can train in a way that targets improving your usage of a certain muscle fiber type.” In other words, your fiber-type ratio and the fuel the fibers mostly utilize aren’t set in stone. “If someone trains in the way that favors slow-twitch, for example, you may start to see a shift where some of the fast-twitch muscle fibers start acting a bit more like slow-twitch,” explains Mincemeyer. “For example, someone who trains for marathons and other endurance events may start to see their body becoming more efficient at utilizing fat for fuel because their body adapts to recruiting the slow-twitch fibers.” That runner may find that instead of slurping down more sticky, sweet energy gels, a handful of almonds—which are higher in fat—will give them more energy and help them feel better during a long run.

So, How Can You Boost Your Metabolism?

person doing oblique crunches


“In order to have a thriving metabolism, we can engage in strength training to build more muscle mass, and match our calorie intake with how many calories our body uses, or ‘burns,’ a day,” notes Mincemeyer. Let’s examine why these are winning strategies.

Eat enough calories.

“Metabolism is influenced by many factors, one of the biggest factors being our calorie intake,” says Mincemeyer. “Tips and tricks you may often see are things like eating hot peppers or drinking apple cider vinegar; however, most of these tactics to boost metabolism would only barely increase metabolism temporarily, if at all. Instead, the best thing we can do is support our metabolism by eating enough calories.” Mincemeyer explains that chronic dieting actually causes your metabolism to slow down. “When our caloric intake is lower than our caloric expenditure, our body can sense that, and over time, [it] automatically slows the metabolism to match this new, lower intake,” she says. “Your body doesn't know the difference between a self-induced calorie restriction (a diet), vs. being stranded on a desert island.” Because the body is highly adaptable and in the business of survival, slowing the metabolism if there’s a perceived caloric shortage is an innate protective mechanism that kicks in to prevent starvation. “This is as automatic of a process as your body shivering when it's cold to help warm the body back up,” Mincemeyer explains.

Engage in strength training regularly.

Fitness experts and trainers are constantly stressing the importance of weight lifting and resistance training for a reason: it’s the best way to build lean muscle mass. And, if you are looking to boost your metabolism (aren’t we all?), increasing your lean muscle mass is the most effective route to take. “Muscle mass is more ‘metabolically active,’ meaning it increases metabolic rate,” says Mincemeyer. So, if you want to burn more calories during the day, don’t let heavy weights intimidate you. Building strength and developing more muscle mass will have your body cranking through more calories even once the workout is over. “It's important to support that higher metabolic rate, then, with a higher calorie intake,” advises Mincemeyer.

Related Stories