The Top 8 Metabolism Myths Busted


Trainers, friends, and nutrition know-it-alls love to tell you that this ingredient will boost your metabolism, or that habit will slow it down. But is there any truth to these metabolism myths?

Let’s get a bit science-y first. You’ve heard of the energy balance equation: “energy in” versus “energy out,” right? The calories you eat are the energy in. Your metabolism is the energy out. Basically, it’s how efficiently you’re able to digest, process, use, and store energy. Of course, like all things science, metabolism is more complicated than simply putting your foot on the gas to make your engine run faster. It’s a complex system of calorie-burning activities.

Energy Out


Resting Metabolic Rate (RMR)

Most of your energy needs (more than 60 percent) are required for basic functions that keep you alive. When you’re resting, breathing, thinking, and pumping blood, you’re still burning calories, without even trying.


Thermic Effect of Food (TEF)

Think of this as your post-meal burn—about 10 percent of your energy is required to eat, digest, and process food.


Physical Activity (PA)

Hitting the gym? Any planned activity you do, like brisk walking, running, or swimming falls into this category. For most people, this energy demand is actually very small and could be increased.


Excess Post-Exercise Oxygen Consumption (EPOC)

After you exercise, there’s a period where your body continues to burn calories to restore itself to pre-exercise levels—known as the “after burn.”


Non-Exercise Activity Thermogenesis (NEAT)

Outside of the gym, this is any other movement you do to when going about your life, like moving, standing, and fidgeting.

All five of these factors are highly variable. But the idea of being able to crank them up a bit to burn even more calories, by doing something that requires very little effort on your part, is obviously very appealing. Enter the metabolism myths …

Myth #1: Exercise Revs Your Metabolism

Simple truth: Yes

The amount of calories you blitz when working up a sweat isn’t huge (compared to how quickly you can eat them!), but it can help. Regular aerobic exercise, particularly high-intensity interval training (HIIT), not only burns calories while you’re doing it, but also creates an after-burn effect, increasing your metabolism post-workout. Strength training, which builds more calorie-munching muscle, can increase your resting metabolic rate slightly, too. Any other movement you can add to your day—upping your hourly steps, taking the stairs, or opting for a standing desk, even fidgeting more—can help, too.

Myth #2: Eating Spicy Foods Boosts Your Metabolism

Simple truth: Yes

Eating chile peppers, which get their spiciness from phytochemicals called capsaicinoids, can increase your metabolism slightly. The theory is, they increase the heat your body produces (which takes energy to produce) and enhance fat breakdown. They can also help you eat less (about 74 calories less, which isn’t much!) and make you feel fuller for longer. You do need to eat at least 2 milligrams of capsaicinoids (about one tenth of a chile pepper) to get the effect. A drop or two of hot sauce alone isn’t going to melt all your unwanted fat away, but adding some heat regularly to what you eat may help a little.

Myth #3: Thin People Have Faster Metabolisms than Overweight People

Simple truth: No

This is probably the biggest metabolism misconception. Just like a big car needs more fuel to run than a small car, a larger body requires more energy to stay alive than a smaller body. There are two medical conditions that are the exception: Cushing’s Syndrome and having an underactive thyroid can cause a slow metabolism and weight gain. But for most people, since metabolism decreases as weight goes down, it’s important to try to keep your metabolism ticking in other ways after weight loss.

Myth #4: Going on a Diet Messes with Your Metabolism

Simple truth: Yes

The recent Biggest Loser study, although an extreme example, shows how losing weight too quickly can really mess with your metabolism. By eating too few calories, you push your body into conservation mode, slowing down natural processes to save energy. The trick to healthy calorie cutting? Do it slowly and don’t go below your resting metabolic needs—slow and steady weight loss wins the race. And bear in mind, after you’ve lost weight, your energy needs decrease by about 20 calories per kilogram lost (or 10 calories per pound). If you go back to eating the same amount of food as before, you’ll just slide back.

Myth #5: Drinking Green Tea Speeds Your Metabolism

Simple truth: Yes

Green tea may soothe your weight-loss woes. Many studies have shown it can help you manage your weight, particularly if you’re looking for that extra little boost to offset a slower metabolism (see Myth #4) and prevent weight creeping back on. A group of antioxidants, called catechins, and caffeine team together to stimulate the nervous system and increase the amount of calories you burn (more than what caffeine alone would!) All forms of green tea, including oolong and white contain these ingredients, with white tea containing the highest levels. Slight damper alert: If you already have lots of caffeine in your day, the metabolic effect from the green tea may not be as noticeable.   

Myth #6: Sipping Lemon Water Wakes Up Your Metabolism

Simple truth: No

Drinking a cup of warm lemon water first thing in the morning is an age-old dieting ritual. Many swear it can detoxify, aid digestion, and “release” excess fat. (If only releasing stored fat were that simple!) This habit does little more than hydrate you and deliver a small dose of vitamin C. No magical fat-burning powers here, sorry.

Myth #7: Keeping Cool Burns More Calories

Simple truth: Yes

Keeping the air around you cool may actually fire up your own internal thermostat. When the temperature drops even just slightly, your body activates a “good” fat called brown fat, which burns extra calories to warm you up. Lowering your home’s temperature to around 66 degrees even just for a couple of hours appears to be enough to stimulate this increased metabolism.

Myth #8: Drinking Really Cold Water Burns Calories

Simple truth: Possibly

So if keeping cool on the outside burns a few extra calories, what about keeping cool on the inside? One small study shows promising results: Drinking 500 milliliters (17 fluid ounces) of water increased metabolism by 30 percent—almost half of the extra calories burned were due to the body expending energy to warm the water up to body temperature. But before you starting gulping gallons of icy water, you should know research measuring the effect of water on metabolism have had mixed results.  

The Real Formula for Boosting Your Metabolism

Generally speaking, everyone’s metabolism works pretty well. But just as you’d maintain your car, you need to fill your body with the right fuel to ensure it runs as smoothly and efficiently as possible. The best metabolism-boosting strategy involves starting your day well rested, after 7 to 9 hours of sleep, to keep your hunger, stress, and sugar-metabolizing hormones balanced. Follow that up with a breakfast that’s high in protein and whole grains, to get your body working soon after rising. Always keep a bottle of water handy to keep your engine well lubricated. Avoid skipping meals, and when you do eat, say no thanks to ultra-processed foods. Go easy on the booze, too; your body will focus on getting rid of the alcohol first, before metabolizing the food. And while you’re at it, call in reinforcements: nurture your gut microbiome so the good bugs can help you digest foods efficiently and maximize your metabolism potential. All of these habits, along with exercise and getting more steps in your day, can set you on a path to a healthier, more energy-efficient you.

7 Comments   Join the Conversation

7 CommentsLeave a comment

  • Thank you Tracy Morris for such a organized and concise article on the science of understanding how your body burns calories. This is an article I will keep handy to share with others.

  • Thank you, loosing weight can be stressful with so many myths.Everyone has a different method to loosing weight, from the doctor, the nutritionist, to the weight trainer. Especially the intake of water. The information your provided is very helpful. Can you please forward this to my email address at home. I would love to review and share this information with others out side of the work place.

  • Thank you Tracy for this instructive article. I would like to know how can we calculate our Metabolism Rate and what is the ideal range?

    Thank you

  • Hi Tracy. I loved reading your article. It is consise and to the point, no mumbo jumbo that is way above the average person’s head. Great advice.
    Thanks again.
    Karen Mordecai-Jones (I use to work with your Mum x)

  • the biggest loser study was a joke that used made up formulas that gave fake results. there is no starvation or “conservation” mode. read the actual minessota starvation study and realize that those man were eating at 50% deficit for 6 months and their metabolism was not affected.

If you have questions about a Fitbit tracker, product availability, or the status of your order, contact our Support Team or search the Fitbit Community for answers.

Please note: Comments are moderated and may not appear immediately after submission.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.