When you lose weight, your body goes through a series of changes both externally and internally. One extremely important internal function that is affected by weight loss is your metabolism.
To learn how your weight loss affects your metabolism, POPSUGAR spoke to Avigdor Arad, PhD, RDN, CDE, director of the Mount Sinai Physiolab, and Holly Lofton, MD, director of the medical weight management program at NYU.
What Is Metabolism and How Does It Work?
Before going any further, it's important to understand exactly what your metabolism is and how it works. "Metabolism relates to the ability to produce energy from fat, from sugar, from protein, and also to store energy," Dr. Arad told POPSUGAR.
Essentially, your metabolism works by converting the energy from food and liquid to either energy it can use immediately, in the form of sugar, or stored energy that it will use later, in the form of fat, Dr. Arad explained.
When you hear people talk about metabolism, they typically mean their metabolic rate, which is the number of calories (or how much energy) they burn in a period of time. Everyone has a different resting metabolic rate (RMR), the amount of energy/calories your body needs for things like your lungs, heart, brain, and muscles to function in the basal state (before you exercise and eat), Dr. Arad said.
In order to figure out what your RMR is, Dr. Arad recommends getting an RMR test (typically around $250), which is offered by specialized clinics like the Mt. Sinai Physiolab.
How Weight Loss Affects Your Metabolism
The connection between your metabolism and weight loss has to do with your body's energy production. When you lose weight, you lose both fat and muscle tissue, which causes your body to produce less energy due to the loss of active tissue that is found in muscle.
As a result, "when we lose weight, we actually lower our metabolism," Dr. Lofton said. Because your body is burning fewer calories, it's important to eat fewer calories to prevent gaining back the weight you've lost, Dr. Arad said.
Everyone has different caloric needs, and there isn't a universal amount of calories we can recommend you eat to prevent weight loss. The USDA dietary guidelines recommend adult women consume 1,600 to 2,400 calories a day and adult men consume 2,000 to 3,000 calories a day. To get a generic idea of how many calories you should eat to lose weight, use this formula. If you'd like to determine your exact daily caloric needs, we recommend speaking to a registered dietitian or specialists like Dr. Arad and Dr. Lofton.
How to Boost Your Metabolism
A slow metabolism may not sound ideal, but according to Dr. Lofton, it isn't necessarily a bad thing. If you're interested in boosting your metabolism, Dr. Arad recommends eating more healthy fats and protein and consuming less sugar. Both doctors also advise increasing your physical activity with workouts that will increase muscle mass, like weightlifting.
The reason you should add weightlifting to your workout routine is because muscle is an active tissue that produces a lot of energy, Dr. Arad explained. "If you build more muscle and you have more muscles that require energy, then you're going to increase your metabolic rate," he said. Here's a four-week strength-training plan to get you started.