Is Metabolism The Cause of Weight Gain?​

If you’re concerned about weight gain, you may have heard that a slow metabolism is to blame. However, this isn’t actually true! To understand why, it’s important to learn more about metabolism and how energy is used in the body.

What is Metabolism?

Metabolism refers to the process by which our bodies break down food into energy. This is achieved by taking calories from food and converting them into energy that cells can use.

What is Metabolic Rate?

Metabolic rate is the amount of energy used by the body per unit of time. It accounts for about 70% of our total energy use each day. Basal Metabolic Rate (BMR) or Resting Metabolic Rate (RMR) is often used to measure metabolic rate at rest. BMR/RMR is the energy needed for basic body functions such as breathing, organ function, cell survival, and maintaining hormone levels.

Several factors impact metabolic rate, including:

• Sex: People assigned male at birth tend to have higher metabolic rates than those assigned female.
• Age: Younger people have higher metabolic rates, which decrease with age.
• Body Composition: Increased height, muscle mass, and fat mass (obesity) all increase metabolic rate.
• Temperature: Metabolic rates increase in hotter environments (due to sweating to cool the body) and colder environments (due to heat generation).

Contrary to popular belief, people with higher body weights have higher metabolic rates. However, their metabolic rates decrease when they lose weight. This is one reason why maintaining weight loss can be challenging. With weight loss, a decrease in metabolic rate and an increase in hunger hormones can make it challenging to maintain weight loss.

Nonetheless, it’s important to note that energy expenditure involves more than metabolism and metabolic rate. Losing weight and keeping it off is still possible, and other factors play a significant role.

Other Ways Energy is Used in the Body

Aside from BMR/RMR, there are two other ways that the body uses energy:

1. Diet-Induced Thermogenesis: Around 10% of all the energy used by the body in a day is used for digesting, moving, absorbing, and storing food. There is not much variation in this energy use.
2. Physical Activity: This includes non-exercise activities like walking around the house, walking to the car, and fidgeting, as well as intentional exercise. Physical activity has the most room for variation in the amount of energy used, particularly the non-exercise part of the day (also known as nonexercise activity thermogenesis). The best way to increase energy use is to avoid being sedentary throughout the day.

In summary, total energy use over the course of the day is the sum of BMR/RMR, Diet-Induced Thermogenesis, and Physical Activity. BMR/RMR is higher with higher body weights but is not the main contributor to weight gain. Diet-Induced Thermogenesis accounts for around 10% of energy use and is relatively stable. Physical activity is a combination of intentional exercise and movement throughout the day, and it offers the most opportunity for intervention. By finding ways to move more over the course of the day, you can have the greatest impact on increasing your daily energy expenditure.

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