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A Doctor Debunks 8 Myths About Metabolism and Weight Loss

By Venus Ramos, MD

In this article:


‌‌‌‌What Is Metabolism In The Body? 

When talking about diet and exercise, metabolism is a term that will often come up, often as a focus topic when weight loss is the goal. But what exactly is metabolism?

Your body’s metabolism is the sum of all the physical and chemical processes that take the energy (or calories) in the food and drink you consume and converts it into the energy needed for your body to function and survive. 

So, how is metabolism related to weight loss? Your body weight results from the difference between the energy you release into your body and the energy you utilize. That’s why metabolism is a key factor in determining body weight. 

Most everybody would like to have a fast metabolism, especially if they’re looking to lose weight. However, there’s a lot of misunderstanding about it, and who wants to waste time on unfounded tactics when you’re trying to make decisions that affect your health? Let’s sort out the myths and the facts surrounding metabolism.

‌‌‌‌Myth: Eat Fewer Calories To Boost Your Metabolism

It’s true that weight loss is often about creating an energy deficit so that you’re consuming fewer calories each day than your body uses. However, long-term weight loss success is not as simple as eating less. 

If you drop your calorie intake too low, then your body goes into starvation mode. This means the body interprets the reduced calories as a signal that you are experiencing a famine, so it shifts to requiring less energy to perform the same functions. In other words, your metabolism slows down, and your weight loss comes to a halt. Weight gain can even occur.

‌‌‌‌Myth: Thin People Have Higher Metabolisms

It takes more energy for a larger body to function compared to a smaller body, so an overweight person tends to actually have a faster metabolism than a thin individual. There are a couple of exceptions, however. People with an underactive thyroid or those with Cushing’s Syndrome (a disorder caused by high levels of cortisol) may be overweight while having a slow metabolism.

‌‌‌‌Myth: Your Metabolism Slows Down With Age

Basal metabolic rate (BMR) is known to decrease as people get older. BMR is the energy, or calories, required to keep your body functioning while at rest. However, aging itself is not the reason behind the slowdown of your metabolism. Lifestyle factors play a major role in your metabolic decline. 

As people age, they tend to become less physically active without changing how they eat. So their BMR decreases and they gain weight.

‌‌‌‌Myth: 1 Pound Of Muscle Burns 50 Calories At Rest

In reality, 1 pound of muscle only burns about 6-7 calories at rest. So if you were to put in the work at the gym, and gained 5 pounds of muscle, you would only be increasing your BMR to burn about 35 more calories each day. So, muscle tissue at rest does not contribute a whole lot to your total energy expenditure. 

Perhaps now you’re wondering what is responsible for burning the bulk of your calories at rest. The lungs, heart, brain, liver, and kidneys consume the majority of calories, accounting for approximately 80% of your BMR.

‌‌‌‌Myth: You Can Make Up For A Bad Diet With A Good Workout

Exercising won’t help you achieve your weight loss goals if you are eating foods that are high in calories and poor in nutrition. Another fact: exercise does not make up the bulk of your calorie-burning in a day. Unless you are a high-level athlete, exercise accounts for about 10-30% of the calories you burn each day. Your BMR, meanwhile, accounts for 60-80% of your total caloric expenditure.

Now, there is evidence that vigorous exercise such as high-intensity interval training can rev up your metabolism for several hours (as much as 24 hours and in some cases longer) after your workout. However, this effect is temporary, only occurring on the days you exercise. 

If your answer to the temporary nature of the metabolism boost is to exercise vigorously every day, that plan may backfire on you as well. Your metabolism does not function efficiently if you don’t allow your body time to rest and recover. Too much stress on your body puts it into an inflammatory state, which affects the balance of your hormones, disrupting your metabolism.

‌‌‌‌Myth: Eating Small, Frequent Meals Will Boost Your Metabolism

Eating small meals throughout the day may help you with portion control, but it doesn’t speed up your metabolism. Researchers studied individuals eating 6 meals per day compared to those eating 3 meals per day. They found there was no difference in 24-hour fat oxidation rates (a measure of metabolism). Furthermore, they noted that eating more meals may cause increased feelings of hunger, so it could result in greater calorie consumption.

‌‌‌‌Myth: Late-night Eating Slows Down Your Metabolism

When people gain weight, they may blame those extra pounds on a slower metabolism caused by late-night snacking. It’s not necessarily the timing of your eating that results in weight gain. It’s more likely the quality and quantity of the food you are eating. It’s fine to eat snacks at night if you are hungry. Just refrain from mindless snacking and don’t go overboard on the calorie intake.

‌‌‌‌Myth: Certain Foods Can Speed Up Your Metabolism

There have been some studies demonstrating that consuming cayenne peppers (capsicum) can boost metabolism. However, it is a short-lived and insignificant increase. 

Research on green tea reveals that it contains a compound called epigallocatechin gallate (EGCG) which can increase your caloric burn. One meta-analysis found that 250 mg of EGCG intake resulted in an average of 100 additional calories burned per day.

Another meta-analysis showed that green tea led to only minor results in weight loss for obese or overweight individuals. Green tea also did not demonstrate any benefit in helping to maintain whatever weight loss had been achieved. 

That being said, green tea does have antioxidant effects that can be beneficial for your longevity. So if your goal is to lose weight, regular exercise and a nutritious diet is still the best foundation for success. However, given the health benefits of green tea, it can certainly be used to supplement that strategy to enhance your weight loss results.

To get the 250 mg of EGCG that researchers found to be effective for increased caloric burn, you can drink about 3 cups of green tea each day. That amount does vary between individuals depending on their caffeine intake and their natural metabolism. Because green tea is a stimulant, it is wise to consult with your healthcare provider before starting it if you have a medical condition or are taking medications.

‌‌‌‌Proven Ways to Boost Your Metabolism

Eat A Balanced Diet

A healthful diet with plenty of fruits and vegetables as well as protein and healthy fats will give you the nutritious support required for a strong metabolism. 

Your body uses energy (burns calories) when you eat because it has to digest and metabolize the food. This is called the thermic effect of food (TEF). Both fiber and protein tend to have a higher TEF than other foods, so they can help boost your metabolism.

In one study, participants who consumed more than 40 grams of fiber daily were able to burn at least 92 more calories per day. Other studies showed that high protein intake was able to increase calorie burn by about 80 to 100 calories daily.

Good sources of protein include lean meats, beans and lentilsnuts and seeds, and plant-based protein. And whole grains, fruits, and vegetables are essential for getting enough fiber. If you don’t get enough protein in your diet, protein powders are an easy way to boost your intake. 

Drink Adequate Amounts Of Water

When your body doesn’t get enough water, it signals your metabolism to slow down. At least 4 to 6 cups of water each day is likely enough to avoid dehydration for most healthy people, but this varies between individuals depending on factors like weather and physical activity. If you do large amounts of prolonged physical activity, electrolytes can help you stay hydrated.

One small study revealed that a water intake of 500 mL increased metabolic rate by 30%. 

Another benefit of drinking water is the prevention of overeating, as people often mistake thirst for hunger.

Get Enough Sleep

Lack of adequate sleep can interfere with the regulation of your blood sugars. Without sufficient blood sugar, you will be unable to fuel your body’s metabolic processes. 

Poor sleep also disrupts the balance of your hunger hormones—leptin (which reduces appetite) and ghrelin (which stimulates appetite). Leptin resistance can develop which keeps you feeling hungry and hinders your metabolism. If you have a hard time falling or staying asleep, melatonin supplements may help. 

References:

  1. Jéquier E. Energy expenditure in obesity. Clin Endocrinol Metab. 1984 Nov;13(3):563-80. 
  2. McClave, Stephen A.; Snider, Harvy L. Dissecting the energy needs of the body, Current Opinion in Clinical Nutrition and Metabolic Care: March 2001 - Volume 4 - Issue 2 - p 143-147
  3. Simpson RJ, Campbell JP, Gleeson M, et al. Can exercise affect immune function to increase susceptibility to infection? Exerc Immunol Rev. 2020;26:8-22.
  4. Ohkawara K, Cornier MA, Kohrt WM, Melanson EL. Effects of increased meal frequency on fat oxidation and perceived hunger. Obesity (Silver Spring). 2013 Feb;21(2):336-43.
  5. R. Hursel, W. Viechtbauer, A. G. Dulloo et al., “The effects of catechin rich teas and caffeine on energy expenditure and fat oxidation: a meta-analysis,” Obesity Reviews, vol. 12, no. 7, pp. e573–e581, 2011
  6. Jurgens TM, Whelan AM, Killian L, Doucette S, Kirk S, Foy E. Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane Database of Systematic Reviews 2012, Issue 12.
  7. Karl JP, Meydani M, Barnett JB, Vanegas SM, Goldin B, Kane A, Rasmussen H, Saltzman E, Vangay P, Knights D, Chen CO, Das SK, Jonnalagadda SS, Meydani SN, Roberts SB. Substituting whole grains for refined grains in a 6-wk randomized trial favorably affects energy-balance metrics in healthy men and postmenopausal women. Am J Clin Nutr. 2017 Mar;105(3):589-599. doi: 10.3945/ajcn.116.139683. Epub 2017 Feb 8. Erratum in: Am J Clin Nutr. 2017 Aug;106(2):708.
  8. Veldhorst MA, Westerterp-Plantenga MS, Westerterp KR. Gluconeogenesis and energy expenditure after a high-protein, carbohydrate-free diet. Am J Clin Nutr. 2009 Sep;90(3):519-26. doi: 10.3945/ajcn.2009.27834. Epub 2009 Jul 29. 
  9. Johnston CS, Day CS, Swan PD. Postprandial thermogenesis is increased 100% on a high-protein, low-fat diet versus a high-carbohydrate, low-fat diet in healthy, young women. J Am Coll Nutr. 2002 Feb;21(1):55-61.
  10. Boschmann M, Steiniger J, Hille U, et al. Water-induced thermogenesis. J Clin Endocrinol Metab. 2003;88(12):6015-9. 
  11. Morselli L, Leproult R, Balbo M, Spiegel K. Role of sleep duration in the regulation of glucose metabolism and appetite. Best Pract Res Clin Endocrinol Metab. 2010;24(5):687-702.

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