Nutrition month: Metabolism facts and fiction

Mar 15, 2021


You probably have heard the word “metabolism” thrown around. People often say, “Your metabolism slows as you get older,” or “He doesn’t gain weight because he has such a quick metabolism.” But are any of these statements true? What is metabolism anyway—and how does it affect your weight?

What is metabolism?

Every process in your body requires energy. Digesting food, breathing and pumping oxygen to your blood all involve chemical processes that keep you alive and functioning.

The minimum amount of energy you need to continue all these processes is known as basal metabolic rate (BMR). Often, when people refer to a “slow metabolism,” they’re actually referring to a low BMR.

Knowing your BMR can help you understand your basic energy needs. You get energy through calories—so your BMR helps you calculate the minimum amount of calories you need per day. However, the vast majority of people need to consume more than their BMR caloric needs. Your age, gender, exercise routine and genes all contribute to how many calories you need per day to keep your energy up.

Busting metabolism myths

Some people claim to have been born with a “fast metabolism.” There is a genetic component to metabolism, but your lifestyle and health habits have a bigger impact on your metabolism than you may think.

The most significant factor that affects your metabolism rate is muscle mass. The more muscle you have, the more efficiently your metabolism works. For example, men may have faster metabolisms because many men tend to have more muscle mass and less body fat than women. Additionally, people tend to lose muscle mass as they age, which explains why people experience a slowed metabolism as they get older.

How does metabolism affect my weight?

Some people claim to have trouble losing weight because of a “slow metabolism.” Your eating habits do affect your metabolism, but the truth is more nuanced than many people think.

When you go on crash diets or severely restrict your calorie intake, your body still needs to find energy somewhere. As a result, your body may start breaking down muscle for energy. When you lose muscle mass, your metabolism slows. After you stop a crash diet, you may rebound and gain weight back quickly, because you’ve lost muscle mass.

The best way to sustainably lose weight is to burn more calories than you consume, while still meeting the caloric needs of your BMR. This might mean you lose weight more slowly—but it will be easier to keep the weight off if you don’t burn through muscle mass. If you have trouble losing weight, you may be inaccurately estimating how many calories you’re consuming. Unless you measure your portion sizes, it can be easy to overconsume healthy but calorically dense foods, such as nuts, peanut butter or olive oils.

In rare cases, an underlying condition may affect your metabolism, such as hypothyroidism (underactive thyroid gland) or Cushing’s syndrome. Working with your healthcare provider to manage underlying conditions can help you achieve and maintain a healthy weight.

Can I boost my metabolism?

You might be tempted by energy drinks, shakes or supplements that claim to increase your metabolism and boost fat loss. And while you might notice some results initially, these products are usually not effective long-term.

The one proven way that you can boost fat loss is through regular exercise. A well-rounded exercise plan includes a combination of aerobic activity, strength training and stretching. Aim to incorporate strength training two or more days per week to increase your muscle mass—this will have the biggest impact on your metabolism. You can also increase your activity levels through small daily tweaks, such as taking the stairs, going on a 10-minute walk around your neighborhood or parking at the back of the lot when running errands. And remember to always talk to your provider before starting a new exercise regimen.

Healthy weight maintenance

There is no magic pill for increasing metabolism or losing weight. However, if you are having difficulty achieving a healthy weight, you may consider working with a registered dietitian. Dietitians are nutrition experts who can help you understand food labels, calories, serving sizes, food groups and more.

Everyone is unique—a nutrition plan that is beneficial and sustainable for you may not work for someone else, and vice versa. A dietitian can write a unique, customized plan to help you achieve and maintain your weight loss goals.

If you have symptoms of an underlying condition, or need help finding a dietitian, speak with a provider about next steps.