8 Myths About Metabolism You Need to Stop Believing

It’s time you know the burning truths about your metabolism.

Most of us know the basic formula for weight loss: If calories out exceed calories in, the pounds will fall off. But what sounds so simple can actually be a bit complicated when you consider the “calories out” half of the equation. 

Obviously, physical activity — whether a workout at the gym or simply walking up stairs — requires energy. But our bodies also use calories to keep the lights on — our heart needs energy to pump, and our lungs need energy to enable us to breathe. This is called our “resting metabolic rate,” and along with the calories we burn through exercise and digesting food, it makes up what most of us refer to simply as our “metabolism.”

Your resting metabolic rate is responsible for about 60 percent of the calories you burn. As a result, “it’s really the main target of both substantiated and unsubstantiated weight loss [strategies],” says Jonathan Mike, PhD, an exercise scientist and strength coach. Yet most of us don’t really know how our metabolism even works — we simply characterize our internal engine as “fast” or “slow,” and if it’s slow, we want to speed it up. The result? We eagerly buy into mainstream myths about metabolism that may do more harm than good. 

Myth #1: Breakfast is the most important meal of the day because it wakes up your metabolism.

We’ve all heard it before: A substantial breakfast is the key to waking up a sluggish metabolism after a night of sleep. But a giant plate of eggs and bacon may not be all it’s cracked up to be: In a 2014 study in the American Journal of Clinical Nutrition, dieters who ate breakfast lost no more weight than breakfast-skippers did.

In fact, downing a big breakfast may actually be a bad thing: It may delay your body’s shift from parasympathetic mode — the rest-and-restore half of your nervous system — to the more metabolically active sympathetic mode, says Roy Martina, MD, author of Sleep Your Fat Away. “During the night, the nervous system is in parasympathetic mode,” he explains. “That’s where we digest food and restore our body.” If you start your day with a big breakfast, you divert your body’s attention back to digestion and rest — and as a result, the calories you consume are more likely to be directed to your fat reserves, he says. 

His advice? Don’t eat first thing after waking up if you’re not hungry. “Postpone breakfast as long as you can,” Martina tells Yahoo Health. “The reason for that is this: We can store unlimited amounts of fat, but we can only store a certain amount of sugar in our body.” So if you delay consuming carbs, your body will burn through its sugar reserves — then move on to torching fat. Of course, if you’re famished come 7 a.m., you should eat, but try to keep it light. “Just eat enough that you feel OK,” advises Martina.

Myth #2: You need to eat every three hours to boost your metabolism. 

You can blame bodybuilders for the six-meals-a-day gospel. “Bodybuilders eat 5,000 calories a day — and most aren’t going to have three meals of 1,500 calories each,” says Mike. “They’ll typically break it up.” 

For serious weightlifters — and the rare people who have naturally revved-up metabolisms, who Martina calls “fast burners” — grazing all day makes sense. But for the rest of us — who eat, say, 2,000 calories a day — there’s no metabolic motivation for spreading our calories out over six meals. 

Need proof? In a British Journal of Nutrition study, when overweight dieters ate either three or six meals a day, with the same total number of calories, they lost the same amount of weight. “Smaller, more frequent meals do not speed metabolism, compared to the same total calories and macronutrients consumed in larger, less-frequent meals,” Mike says. 

Plus, if you’re eating multiple times a day, you may end up overeating, allowing your mini meals to turn into full-size ones, says Michael Jensen, MD, an endocrinologist and professor of medicine at the Mayo Clinic.

Myth #3: Skipping meals reduces your metabolism.

If you don’t eat dinner, will your metabolism take a nosedive? Probably not. In order for your body’s burn to plummet, you need to restrict your calories to the point that you feel deprived, says Martina. And one missed meal isn’t enough to create a serious energy deficit — it’s only when you follow a low-calorie diet for a long time that your body goes into starvation mode, forcing it to use energy more efficiently (i.e. to burn fewer calories), he says. “Skipping one meal will never do that.”

Of course, if you skip a meal, your body won’t experience the small metabolic boost that occurs after eating — but any drop in your burn rate will be so small that it’d be “difficult to detect,” says Jensen. So why are chronic meal-skippers often overweight? “Skipping a meal might make you overly hungry, so you overeat at your next meal,” Jensen says. In other words, it’s a matter of subsequent meal size — not metabolism.

Myth #4: Overweight people have a slow metabolism, and skinny people have a fast one. 

It seems obvious: The fatter you are, the more sluggish your metabolism, right? “As a rule, that’s actually not true,” says Jensen. In fact, he adds, “there are as many skinny people as overweight people with low metabolisms.” Sure, there are slim people with lightning-fast metabolisms. “They cannot sit down for a long time — they’re kind of hyperactive,” Martina says. “They burn so much energy that they can eat much more and get away with it.” But more often, slim folks are simply in tune with their bodies — they eat only what they need, and nothing more. If they do overeat at one meal, they tend to naturally compensate at the next one, preventing them from gaining weight.

And, the truth is, body weight is actually a pretty poor predictor of metabolism — body composition (i.e. how much muscle you have, versus fat) is much more important. “If you have two people, both 180 pounds, and one has 20 pounds of fat and one has 50 pounds of fat, the person with less fat, i.e. more muscle, is going to burn more calories,” says Jensen.

As a general rule, however, overweight people — especially those with some amount of muscle — torch more calories per day than skinny folks, since bigger bodies require more calories for everyday functioning. So why are heavy people still carrying extra baggage if they burn so much energy? Simple: Overweight people may unknowingly consume way more calories than they torch. “Your typical normal-weight person underestimates how much they’ve taken in that day by 20 to 30 percent. Obese people will typically underestimate by as much as 50 percent,” says Jensen. “Someone with a serious weight problem may truly believe they’re taking in a very limited amount of food.”

Myth #5: Some people must eat fewer than 1,000 calories a day to lose weight.

Unless you have a sluggish thyroid, you probably don’t need to drop down to the 1,000-calorie mark in order to lose weight, says Martina. In fact, “the only people I’ve seen who burn that little are people with long-standing anorexia, who weigh about 70 or 80 pounds,” Jensen says. So why do some dieters insist severe calorie-cutting is the only way to move the scale? Because they expect rapid results. “You’d probably lose weight if you cut back to 1,200 or 1,400 calories, but it wouldn’t be quick and it wouldn’t be consistent,” he says. Read: Your weight will drop even if don’t crash diet — but the number on the scale may stay the same for days at a time, leading you to believe the diet isn’t working.

Myth #6: Yo-yo dieting will destroy your metabolism.

Constantly gaining and losing has been linked to a number of health problems (including some serious ones, like endometrial cancer). But ruining your body’s ability to burn calories isn’t one of them. Although it may create temporary metabolic drops, “yo-yo dieting won’t permanently wreck your metabolism,” says Mike. Case in point: In a 2013 study in the journal Metabolism, researchers found that severe weight cyclers — people who’d lost 20-plus pounds on three or more occasions — were able to lose weight, shed body fat, and gain lean muscle just as easily as people with fewer fluctuations.

So why do yo-yo’ers find losing weight to be such a struggle? “They’ve lost and gained, lost and gained, and each time, they give up sooner,” says Jensen. “Since they always regain, it seems harder each time, and they give up easier each time.” Read: Each time they try to diet, they feel frustrated faster — and assume their lack of weight loss is because their metabolism has stalled out. 

Myth #7: You have no control over your metabolism.

Yes, there’s a genetic component to your body’s burning power. “Even if you match up people with the same amount of lean tissue, you have some who burn 400, 500 calories less,” says Jensen. “And that seems to be heritable.” But that doesn’t mean you’re locked into your metabolic rate for life, says Martina. “You can change your metabolism — for example, by packing more muscle onto your frame.”

In fact, gaining muscle through resistance training is one of the best ways to offset the small decline in metabolism that naturally occurs with age, says Mike. “Typically, from age 30 to about age 80, you lose about 15 percent of your muscle mass,” he says. “You can offset that if you start lifting. The earlier you start, the better off you’re going to be as you get older.”

Myth #8: The right diet — lots of green tea and chili peppers! — will boost your metabolism. 

As much as we’d all like to believe the right foods can work a metabolic miracle, the calorie-burning jolt some foods provide isn’t enough to affect your weight, says Jensen. “If I was eating nothing but chili peppers, I might not eat that much — because my mouth would be hot all the time,” he jokes. “But you’re not going to lose weight because of the metabolism effect.”

As Mike explains, metabolism-revving foods really only boost your burn by 4 to 5 percent — and for a very brief time. “You might see a slight increase [in metabolism], but it’s mainly due to a slight elevation in body temperature and sympathetic nervous system activity,” he says.