5 myths about boosting metabolism debunked

By Naveed Saleh, MD, MS
Published July 9, 2020

Key Takeaways

Metabolism refers to the myriad of physical and chemical processes that the body employs to convert or use energy. These physiologic processes include temperature maintenance, breathing, circulation, digestion, muscle contraction, excretion, and neurological function.

Lots of misinformation surrounds metabolism, including beliefs that it can be boosted with ease. There are probably more myths about how to boost metabolism than there are successful techniques to boost it. The danger with these myths is that they can lead people to think they’re burning off more calories than they actually are, which results in overeating and weight gain. 

The following five metabolism myths have been highlighted by the NIH and supported by outside research:

Myth: Certain foods do wonders for your metabolism

Individuals ingesting green tea, caffeine, or hot chili peppers with the hopes of boosting metabolism should be prepared for disappointment.

In one study, researchers found that caffeine did boost metabolism by up to 11%. But, to achieve these results, participants in the study had to drink the equivalent of a cup of coffee every 2 hours over the course of 12 hours. Ingesting that much caffeine on a daily basis is neither a healthy nor a sustainable way to lose weight. 

How about hot peppers? Fans of spicy foods likely know that capsaicin is the chemical that makes peppers hot. Results from a meta-analysis published in Appetite indicated that capsaicinoid ingestion before a meal decreased ad libitum energy intake by 74.0 kcal (P < 0.001), with a minimum loading dose of 2 mg required. However, the eight studies included in the meta-analysis were highly heterogeneous, which undermines the verisimilitude of the results. The authors suggested that decreased food intake after eating capsaicinoids was due to an increased preference for carbohydrates over fats in those who ate the spicy stuff. 

Myth: Exercise leads to sustained increases in metabolism

It’s tempting to think that exercise is so good for you that it will boost your metabolism long after you stop. The reality, however, is that the metabolic impact of an exercise “sesh” dissipates relatively quickly. Research has indicated that the boost may last up to several hours, but it certainly won’t go on for days, weeks, or months.

Results from a small study published in Medicine and Science in Sports and Exercise suggested that in young men who burned off 519 ± 60.9 kcal (P < 0.001) calories during a vigorous cycling session, energy expenditure increased by 190 ± 71.4 kcal during a period of 14 hours post-exercise vs. non-exercise days (P < 0.001).

In other words, although healthy individuals who engage in vigorous exercise may experience some residual metabolic benefits on the days they exercise, these benefits don’t support heavy calorie consumption as some sort of reward. Healthy diets and prudent food choices should be rigorously adhered to regardless of exercise status, with overindulgence avoided both before and after workouts. However nice the thought, a 4-mile jog on Saturday morning fails to abrogate a 1,000-calorie splurge at the ice cream parlor on Sunday night. 

Myth: More muscle burns more calories

Some truly astonishing numbers float around in the exercise world. For instance, a pervasive myth contends that adding 1 lb of muscle burns off between 30 kcal and 50 kcal a day, which if true would be fantastic for fans of strength training. The metabolic benefits of increased muscle mass, however, are much less impressive.

“To suggest an increase of one or two pounds of muscle equates to a notable increase in resting metabolic rate would be inaccurate,” according to the National Council on Strength & Fitness. “Muscle has a low metabolic rate compared to other metabolic tissues at rest. It is estimated that sedentary muscle mass burns about 6 kcals per pound/day or 0.25 calories an hour per pound. This number obviously increases with activity relative to the intensity, but looking it at from a metabolic perspective (METS) that number still does not reach 50 kcal per pound. If it did, a 185 lb person would need 3,885 calories to sustain their muscle tissue, which represents only about 40% of bodyweight.”

In fact, the lungs, kidneys, heart, brain, and liver account for the majority of the body’s total daily energy expenditure—an estimated 80%. The metabolic rate for these organs is 15-40 times more than the equivalent body mass in muscle (and 100 times more than that of fat). In short, resting muscle burns off little energy.

Myth: Eating frequent, small meals boosts metabolism

Popular advice for weight control is that the frequent consumption of smaller meals, or “grazing,” improves metabolism. However, the science supporting this approach as an effective weight-control strategy is lacking, and studies examining the effects of eating frequency on body weight have shown mixed results.

In a randomized, crossover trial published in Obesity, researchers examined the effects of eating six meals per day vs eating three meals per day on 24-hour fat oxidation, as well as qualitative measures of hunger. Of note, daily calorie intake in both groups was equal, and there was a 1-2 week washout before crossover. The researchers not only found that there was no effect on 24-hour fat oxidation rates but also that eating more meals may result in increased feelings of hunger and a greater desire to eat.

Ultimately, the desire to eat fewer or more meals per day is a personal one and should be influenced by which approach makes it easier for any individual to maintain a healthy diet. For instance, if someone has a hard time stopping intake once starting a meal, then three meals may be a good idea. On the other hand, some athletes find that their performance improves by eating smaller but more frequent meals.

Myth: Older people gain weight due to decreased rates of metabolism

Although it’s true that basal metabolic rate decreases linearly with age, older people tend to gain weight for reasons other than age-related changes in metabolism. For one, energy requirements decrease with age, yet many middle-age and older people continue to eat like they did when they were younger. 

“A lot of mid-life weight gain happens because we become less active. Jobs and family push exercise to the back burner. When we do not move as much, we lose muscle and gain fat. As you get older, you may also have trouble regulating your meals with age,” wrote the NIH. “After a big meal, younger people tend to eat less until their bodies use up the calories. This natural appetite control seems to fade as people get older. Unless you pay close attention, big meals can quickly add up.”

As people age, exercise becomes increasingly important to maintain, the NIH added. Eating more healthy foods and consuming foods in smaller portions is also a good idea.

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