6 Metabolism Myths To Stop Believing, According to RDs

Photo: Stocksy/Pedro Merino
When we talk about metabolism, many often immediately pivot to its decline as we age or ways to constantly improve it. And for better or for worse, there is tons of information online that provide tips on how to do so. But like (too) many other topics in health and wellness, a significant amount of this "advice" tends to be based on misinformation versus science-backed facts.

To be fair, the topic of metabolism itself can be pretty confusing. For that reason, we spoke with two registered dietitians to share the top myths about metabolism that we can all completely dismiss this year.

What is metabolism?

Before shining a light on the biggest misconceptions when it comes to our metabolism, let’s first explain what it is. “Metabolism is the process in which our bodies convert what we eat into the energy we need to survive and function,” says Crystal Scott, MS, RD, LD, CDCES, CSP, a registered dietitian nutritionist at Top Nutrition Coaching that specializes in intuitive eating. “Your metabolism helps keep your body moving by converting the food you eat into the energy your body needs to survive; this energy helps you carry out necessary processes like breathing.”

Your metabolism is always in motion, even when you’re sleeping or catching up on your favorite Netflix show. “It never really turns off, because your body is constantly storing and using energy from the food you eat, as well as constructing and disassembling molecules required for maintaining your health,” says Antonio Castillo, RD, a registered dietitian that specializes in sports nutrition and the founder of Nutrition for Performance. “Your metabolism has a significant impact on your health because your body depends on metabolism to carry out all of its operations, including storing and burning fat, controlling sugar levels, and maintaining the function of your neurons.”

Now that we’ve got that covered, let’s go through the top six myths about metabolism to stop believing.

6 common myths about metabolism to dismiss, according to RDs

1. Fasted workouts can burn fat and boost your metabolism

A common belief on fasted workouts—meaning when you exercise without eating anything beforehand—is they can burn fat and boost your metabolism.

On one hand, Castillo says, “brief fasts could boost your metabolism due to norepinephrine levels in your blood [being] dramatically increased, which [can] accelerate your metabolism and tells your fat cells to break down body fat.” However, that doesn’t necessarily mean fasted workouts will result in significant (if any) body composition results.

For one, Scott shares how utilizing fat is different from losing it. “Oxidizing fat during a workout does not mean you’re losing body fat; you are simply switching around the fuel source,” she says. “Research has also shown that working out three times a week fasted versus fed cardio made no difference in body composition and weight.”

The workout itself is generally the factor that can contribute to burning fat and impacting your metabolism long-term. So (please) go ahead and eat a snack before you exercise, because your body requires energy in order to do so.

2. Eating frequently is "better" because it can boost your metabolism

“Many individuals think that increasing the number of meals you consume can raise your metabolic rate and increase the total amount of energy your body burns,” says Castillo. But this isn't accurate. Instead, he says that your daily food intake has a stronger impact on your metabolism than the frequency of your meals. “The same results can be achieved by eating six 500-calorie meals versus three 1,000-calorie meals. In both scenarios, you will burn the same calories at an average thermic effect of food [TEF] of 10 percent.”

In short, it's best to determine a meal cadence you—and your body, your hunger cues, palate, your lifestyle, and so on—prefer, as they will have the same effect on your overall metabolism (and your mental health).

Instead of focusing on innocuous 'food rules' and restrictive habits, try intuitive eating:

3. Your metabolism is higher the more muscle you have

One kilogram of muscle burns 12 calories per day, while one kilogram of fat burns four calories per day, which has led to the belief that gaining more muscle increases your metabolism. However, Scott points out how this isn’t entirely accurate, considering all tissues require and burn calories. Improvements in your metabolism, she says, are more likely a result of adopting a healthier lifestyle, which can include getting enough sleep, eating a well-balanced diet, managing stress, and following a workout regime.

“Individuals who strength train or workout usually consume higher protein intake, which can boost your metabolism by a rate of 100 to 250 kilocalories per day,” says Scott. “Increased intake of micronutrients can also optimize metabolic hormones like triiodothyronine (T3) and thyroxine (T4) uptake.” These hormones help regulate your metabolism, energy levels, internal temperature, skin, hair, and nail growth.

Scott also points out how structured exercise can improve your sleep quality, which can affect workout intensity and your metabolism. “Research shows that poor sleep is linked to a five percent reduction in metabolism and a 20 percent reduction after meals, as well as lower basal fat oxidation,” she says.

So rather than focusing on one specific detail, it’s best to focus on an overall healthier lifestyle—lots of sleep and nourishing foods included—when looking to improve your metabolism.

4. Late-night eating can slow down your metabolism

Nope. According to Scott, there is little evidence to support having a meal past 7 p.m. can slow down your metabolism. There has been some research that suggests having large, mixed meals (meaning they contain all three macronutrients: fat, carbohydrates, and protein) in populations that consume a majority of their food during the night can result in negative outcomes, but the suggested negative outcomes haven’t been consistent—especially when late-night food choices are smaller and more nutrient-dense.

“Nighttime consumption of smaller meals is not harmful and may be beneficial for muscle protein synthesis,” says Scott. It’s especially important to remember that no food is “good” or “bad," especially when thinking about its impact on your metabolism. “I recommend focusing on eating regular, hearty meals and snacks throughout the day instead.”

“Nighttime consumption of smaller meals is not harmful and may be beneficial for muscle protein synthesis,” says Scott. It’s especially important to remember that no food is “good” or “bad," especially when thinking about its impact on your metabolism. “I recommend focusing on eating regular, hearty meals and snacks throughout the day instead.”

5. Drinking cold water can negatively impact your metabolism

In some cultures, drinking cold water is believed to slow down your metabolism, and opting for room temperature water is recommended. There’s also been TikToks advising you not to drink cold water with your meals to boost your metabolism, but Scott says this isn't true.

“Drinking water in general increases metabolic rate by 25 to 30 percent for up to an hour and 10 milliliters/kilograms increases metabolic rate by 25 percent for 40 minutes,” says Scott. “And in fact, cold water further increases metabolic rate as the body works harder to heat it up, [so] drinking more water—no matter the temperature—is considered great for your metabolism.” So yes, cold water can positively impact your metabolism, not hurt it.

According to Castillo, there’s also a belief that drinking lemon water before a meal can boost your metabolism, but he said this isn’t true. The bottom line? Drink whatever type, temperature, or flavor of water you like—just stay hydrated.

6. You can’t control your metabolism

Both experts debunk the common belief that you can’t control your metabolism. “Our genetics help determine our metabolic rate, however, you can help improve and increase metabolism by a few things,” says Scott. Castillo adds, “Natural ways to raise your metabolism include making adjustments to your diet, exercise program, and sleeping schedule.”

A few examples of habits they shared that can improve your metabolism are the following:

  • Add various forms of exercise to your routine: “Exercise at least three times per week for both strength training and cardio, as well as increasing intensity,” Scott says. Weight lifting specifically can boost your metabolism, even while at rest, shares Castillo. Not sure where to start? Explore our library of guided workouts.
  • Prioritize sleep: Both sleep and exercise can reduce cortisol levels (the stress hormone). On the other hand, not getting enough sleep can affect hormones such as leptin, a hormone that regulates fullness (satiety), and ghrelin, a hormone that regulates appetite. Adults are generally recommended to get seven to nine hours per night.
  • Boost your water intake: Scott suggests aiming for half of your body weight in ounces of water for proper hydration.
  • Consume more whole foods: “Whole foods have more complex substrates, as well as greater enzyme and metabolism requirements compared to processed foods,” says Scott. “Whole foods also have more micronutrients, which can optimize metabolic hormones.”
  • Increase your protein consumption: “Increasing your protein intake can lessen the decline in [your] metabolism that is frequently linked to fat loss,” says Castillo. Protein also has the greatest increase in the thermic effect of food (TEF), which is the extra calories needed to digest, absorb, and utilize the nutrients in your food. “Dietary protein requires 20 percent to 30 percent of its usable energy to be used for metabolism, which is higher than carbohydrates [five percent to 10 percent] and fat [up to three percent].”

A combination of these habits can help improve your metabolism over time, even if you’ve been convinced your metabolism will always remain the same.

The bottom line

Like with many myths, it’s important to know who to take advice from and who to dismiss, especially on social media platforms. “Always do your research on reputable platforms and websites, consult with a professional, look for peer-reviewed articles, and always ask questions,” Scott says. What you shouldn’t rely on are posts that encourage fad diets or make claims without citing referenced or science-based research. And one major red flag to look out for are fitness experts that offer nutrition advice.

Castillo also advises following registered dietitians or medical professionals for helpful posts that share the latest research on various topics, especially your metabolism (rather than influencers, workout instructors, holistic nutritionists, et al.).

TL; DR? The next time you come across outlandish claims that seem too good to be true, experts like Scott and Castillo say to unsubscribe.

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