Have you ever wondered why some people seem to be able to eat anything and everything and never gain weight? Or why you feel like you put on pounds just walking past a bakery?
Neither of these extremes is reality, but our individual metabolism does determine how quickly and efficiently our bodies burn calories.
“Metabolism is the process of your body converting what you eat and drink into usable energy,” says UNC Health sports medicine physician Justin Lee, MD. “This energy not only allows us to be physically active, but it also fuels bodily functions we don’t always think about.”
Energy from what we eat keeps our heart beating, our lungs exchanging oxygen for carbon dioxide and our digestive system working, among other functions.
What determines our metabolism?
Certain factors play a role in determining our basal metabolic rate, which is the number of calories your body needs to function at rest. These factors include height, weight, gender and age. Genetics also play a role.
Basal metabolic rate can be calculated in a lab with special equipment that measures how much oxygen you breathe in and how much carbon dioxide you breathe out. To estimate your metabolism online, try a calculator that uses the Harris-Benedict Equation, Dr. Lee says.
“It can be helpful to know what your basal metabolic rate is to estimate how many calories you should be eating each day, which in turn can help with weight loss,” he says.
Some people have medical conditions that may slow or alter their metabolism, such as hypothyroidism (an underactive thyroid gland), which is common, or Cushing syndrome (which causes abnormally high levels of the hormone cortisol), which is uncommon.
Can you increase your metabolism?
“There are some things you can do to increase your metabolism,” Dr. Lee says. “You can increase your activity levels and you can build more muscle.”
Comparing our bodies to cars may help put metabolism in perspective, he says. Think how much gasoline a big, powerful truck consumes compared to a small hybrid car.
“The more muscle tissue we have, the greater our ability to burn calories when we move and exercise,” he says.
Some research suggests consuming caffeine, eating spicy foods or drinking green tea can boost metabolism, but Dr. Lee’s recommendations are more commonsense. “I tell my patients to eat the best diet they can, lower their stress levels, and get at least seven hours of sleep a night,” he says.
Drinking water can also boost metabolism. Drink water throughout the day and with meals, instead of soft drinks, juice or alcohol.
Does it matter when you eat?
Eating a good breakfast can kick-start your metabolism, Dr. Lee says. Plenty of fiber will help you feel full longer.
Eating dinner earlier in the evening may help prevent weight gain since our metabolism slows at night based on our circadian rhythm, he says. “There’s evidence that eating before 7 p.m. is preferable.”
Does metabolism slow with age?
In general, children have higher metabolic rates than adults because they are constantly growing. They need adequate calories to support their body’s growth. But these calories should come from a balanced diet with lots of lean protein, whole grains, fruits and vegetables.
As we get older, our metabolism tends to slow down, Dr. Lee says, which is why some people might find it difficult to maintain a healthy weight as they age. Older adults might have to eat fewer calories or increase their activity levels to prevent excess weight gain. Dr. Lee recommends limiting processed food and added sugar for people of all ages.
If you have questions about your metabolism or weight, talk to your doctor, or find one near you.