SciTech

Health Talk: Metabolism: Energy processes

Credit: Justin Lin/Staff Credit: Justin Lin/Staff

Many weight loss advertisements use the word “metabolism.” Several weight loss methods claim to be able to change a person’s metabolism to help them lose weight faster and more efficiently. It’s not just weight loss advertisements that associate metabolism with weight; people often credit their metabolisms with preventing weight gain, even if they don’t have the best eating habits. What is metabolism, then, and is it responsible for a person’s weight?

According to the U.S. National Library of Medicine, “metabolism refers to all physical and chemical processes in the body that convert or use energy.” This definition makes it clear that metabolism is not a single entity or process inside a body responsible for weight control; instead, it is the group of all processes related to energy conversion and use. There could be, in fact, thousands of metabolic processes occurring in your body right now, according to KidsHealth.org.

All of these processes can be split into two broad categories: anabolism and catabolism. Anabolism refers to the processes that create new cells and tissues in the body by putting together smaller proteins and molecules, while catabolism refers to the destructive processes of the body; they break down large carbohydrate and fat molecules in food to provide energy to cells. In short, metabolism is responsible for collecting energy from the food people eat and using it to keep them alive. Weight loss is not really an integral function of metabolism, but many people have made this association by simplifying the ideas involved.

The Basal Metabolic Rate (BMR) is what most people are thinking of when they talk about metabolism in connection to weight loss. The BMR is a measure of how much energy a body uses just for its daily upkeep. Every human body needs to perform several metabolic tasks in a day just to stay alive, like ensuring circulation of blood, producing and releasing hormones, building and repairing cells, controlling body temperature, and making sure all systems in the body are functioning. These tasks happen unceasingly and are responsible for a large percentage of daily energy consumption for most people.

According to the Mayo Clinic, the BMR stays fairly constant for most people, and can be responsible for up to three-fourths of daily calorie consumption. Different groups of people have different BMRs: large people, people with developed muscles, young people, and males generally have a higher BMR. A person with a higher BMR will burn more calories in the course of a day than someone with a lower BMR. Does this mean metabolism is in some way responsible for one’s weight?

Not exactly. Weight change is largely controlled by the body’s calorie balance. If people consume more calories than they burn, they gain weight. If they burn more calories than they consume, they lose weight. While part of this burning of calories can be due to BMR, it is also affected by one’s level of physical activity.

Consuming the right amount of food is also important to maintaining a healthy weight. Many fad diets try to make people believe they can lose weight by increasing their metabolism either through eating at special times or by adding special ingredients to their food. However, it is important to know that BMRs, except in extreme conditions or due to disease, are stable and are unlikely to be greatly affected by tactics like this. The body has a self-regulating mechanism and is not likely to change its BMR greatly. People aiming to change their weight should focus on the food they consume and the physical activity they get if they want to see change.