When someone says they have a “fast” metabolism, it’s easy to be not all that sure what the heck they are talking about. Is there really such a thing as a fast versus slow metabolism? And if so, is it possible for us to ramp up our own to have some control over it?
What is metabolism?
First, it’s important to know what exactly metabolism is. “Metabolism is the term that describes a combination of processes that the body uses to convert food into fuel to keep you alive,” Dr. David Greuner, surgical director of NYC Surgical Associates, tells SheKnows. “Metabolic processes include breathing, digesting food, the delivery of nutrients to your cells and the use of energy by your muscles.”
While metabolism is a term most commonly used to describe how the body burns calories, Dr. Luiza Petre, a weight-loss and -management specialist and board-certified cardiologist, says metabolism is so much more than that.
“It powers everything you do, from thinking and eating to moving and growing,” she tells SheKnows. “Without it, you would lack the energy to get out of bed in the morning. The number of calories your body uses to keep you alive and carry out these basic functions is known as your basal metabolic rate — what you call your metabolism. It is the engine that burns calories and is the scale that regulates your energy needs.”
What does it mean to have a “fast” or “slow” metabolism?
While some people can eat whatever they want and remain the same size, some find it hard to lose weight no matter how much they exercise and little they eat. While Petre agrees metabolism is linked to weight, she says it’s helpful to think of metabolism in terms of a car.
“The more you put gas, or energy, in the engine, your metabolism burns it and converts it into mileage, or living,” she says, adding that not all cars are made the same way. “Some get better mileage than the others. Same for people and their metabolism; we are not all biologically created equal.”
What affects your metabolism?
There are several factors involved in how fast your body burns calories, including genetics, gender and age, Greuner explains.
“Typically, men will have a faster metabolism than women, and metabolism for both genders will slow down after age 40,” he says. “Your metabolic rate can also vary from day to day, depending on your diet and activity level.”
Not only that, but as we age, there are actual hormonal changes that take place in our body that affect the way we store or lose fat, Petre says. Specifically, our metabolic rate decreases as we get older because of these differences in hormones. This can include the decrease in estrogen around menopause, she adds.
“We also lose muscle mass as we age, and that makes your body burn less,” Petre explains. “Your body goes into its aging stage as it leaves the growing one. When this happens, your body doesn’t need as much energy as it used to. Also, we lose muscle mass as we age, an average of 3 to 5 percent, every 10 years past the age of 35, and that makes your body burn less.”
How can you improve your metabolism?
While metabolism is mostly determined by genetics and age, there are some strategies that you can use. For example, Greuner notes that what you eat and drink can affect your metabolism, but on a smaller scale.
“Since the body burns more calories when digesting protein than carbs or fats, protein-heavy foods can help boost metabolism around mealtime,” he says. “Spicy foods are known to give a quick temporary boost to your metabolism, whereas green tea can speed up metabolism for several hours.”
However, long-term lifestyle changes, such as exercise, work best to speed up metabolism. Specifically, Greuner recommends weight training because “the body is always burning calories, even while at rest, and muscle tissue burns more calories than fat tissue — which is why men, who are typically more muscular, will generally burn more calories than women.”
Intense aerobic exercise, like HIIT training, will speed up metabolism for several hours after a workout since the higher the intensity, the longer your metabolic rate will remain at a higher level, he adds.
“Maintain consistent workouts, at least 30 minutes per day, to help keep muscle deterioration to a minimum,” Petre recommends. She also says drinking more water will burn additional calories, as it will keep you hydrated and feeling full, and recommends sticking to a diet that is filled with foods that are vitamin-rich, full of minerals and healthy nutrients. Finally, she says to avoid processed and refined foods.
As for what can slow a metabolism, Petre says not eating enough calories or drinking enough water are usually the main culprits.
“Since metabolism slows down between meals, eating erratically and waiting too long to eat may take a toll on your metabolism,” she explains. “Water is a necessary component for the body to process calories, so if you are even mildly dehydrated it can disrupt your weight-loss efforts.”
While your metabolism won’t change overnight, implementing small, long-lasting changes like diet and exercise have the potential to kick-start your metabolism.
A version of this story was published September 2018.