You’ve probably heard the complaint, “I can’t eat like I used to!” from time to time from friends or family members. But a new study in the journal Science found that metabolism may actually not slow down as much before the age of 60 as previously thought. In fact, it remains pretty stable between the ages of 20 and 60, and only slows down slightly after that point. In a lot of ways, this is exciting news—we’re not powerless in the face of our slowing metabolisms after all. But having a better understanding of what metabolism is, how it works, and lifestyle tweaks you can make to speed it up can only help in keeping off unwanted pounds as you age. Here’s everything you need to know.
What is metabolism, exactly?
Every human has a metabolism, and it helps keep us alive. “Metabolism is the chemical reactions in the body that change food into energy,” saysEmily L. Doctor, DNP, nurse practitioner with NYU Langone’s Weight Management Program. “Our bodies need this energy to do everything from moving to thinking to growing.” Specifically, there are a number of proteins in our bodies that control the chemical reactions of the metabolism, and several hormones that help control the rate and direction of the metabolism. “For example, thyroxine is a hormone that is made and released by the thyroid gland,” says Doctor. “Thyroxine plays a key role in determining how fast or slow the chemical reactions of the metabolism are.”
What does it mean to have a “slow” metabolism?
There are a lot of factors that go into how fast or slow a metabolism is. While age is proven to play a small role, that’s hardly all there is to it. “Many things can affect metabolism including how much muscle you have, your thyroid function, your physical activity and the rate at which you lose weight,” says Sonya Angelone, MS, RDN, CLT, registered dietitian nutritionist and spokesperson for the Academy of Nutrition and Dietetics. According to Angelone, the main reason we say that metabolism slows down as we age is that we tend to gain fat and lose muscle as we get older, and fat is less ‘metabolically active’ than muscle. “This is often because people become less active, not just as a natural cause of advancing years,” says Angelone. Metabolism is greatly determined by the number of calories someone burns in a day, which is impacted by how much a person exercises and the amount of fat and muscle in his or her body, referred to as basal metabolic rate (BMR). “Basal metabolic rate (BMR) is a measure of the rate at which a person’s body ‘burns’ energy, in the form of calories, at rest,” adds Doctor. “People with more muscle and less fat generally have higher BMRs, meaning they burn more energy at rest. For example, a person who exercises more not only burns more calories, but becomes more physically fit, which increases his or her BMR.”
Does your metabolism really slow down with age?
Based on this recent study, the biggest takeaway may be that ultimately muscle mass declines as we age, especially after 60, and fat increases. “Our basal metabolic rate declines, and we perceive this as a ‘slowed’ metabolism,” says Doctor. She adds that ultimately it also means that as a society we are consuming more calories than we burn, and we are more sedentary. “I think the important point is that beyond ‘calories in vs calories out’, it’s really about the way the calories are absorbed by the body: burned, excreted, or turned into body mass,” says Doctor. “This emphasizes the importance of continuing to exercise, build muscle and consume high-quality protein throughout our lifespan, even more so as we age.”
Tips for keeping your metabolism fast and healthy
If you’re concerned about your metabolism affecting your weight as you get older, there are things you can do to avoid the middle-age spread. Here are seven of them.
Resistance training
Muscle mass is the basis for metabolism. The less muscle you have the fewer calories you can consume. “People lose muscle as they get older. Rather than devote all your time to walking or biking, you can burn more calories by keeping muscle mass up with resistance training,” says Dr. Michael Jensen, MD, an endocrinologist at Mayo Clinic. “You burn more calories if you have 20 more pounds of muscle than fat.”
Keep moving
Besides resistance training, add interval training to your cardio routine and burn more calories in less time. “For example, run for a minute, then walk for two minutes. Repeat this pattern for 20 to 30 minutes,” says Doctor. “Everyone has a different ability, but find something you can do 20-30 minutes per day and do it consistently five to seven days per week. Even if you park in the back of the grocery parking lot, those small differences add up!”
Lose weight slowly
“If you try to lose weight too quickly, a couple of things happen. First, you will lose more muscle which is metabolically active. This will cause you to require even fewer calories,” says Angelone. “Second, it will stress your body, and your thyroid gland specifically which will cause your body to partly shut down as a survival response. Since it isn’t getting many calories, it will just conserve them and require fewer calories each day.”
Eat high-quality protein to fuel your muscles throughout the day
“Metabolism relies on enzymes which act as catalysts to promote the chains of reactions—enzymes are proteins,” says Angelone. “If you don’t eat enough protein, your body has to break down muscle or stored protein in order to maintain the many chemical reactions that support life.” Adds Doctor, “For an adult, I recommend a minimum of 1.2 up to 2.2 grams of protein per kilogram per day and for the elderly I recommend 1.2-1.5 grams per kilogram per day.”
Aim for at least seven hours of sleep per night
“Research has consistently demonstrated that when we get less than that our cortisol levels increase which causes us to metabolize food more slowly and crave more fattening and starchy foods,” says Doctor. She notes that s four-year joint study by the University of Wisconsin and Stanford University found that adults who regularly slept for only five hours a night increased their levels of hunger-inducing ghrelin by 14.9% and lowered their levels of appetite-suppressing leptin by 15.5%.
Eat breakfast
Studies show that if you start the day with breakfast, you will burn more calories earlier in the day. “If you skip breakfast, your metabolisms have to slow down in order to conserve calories so you can get through your morning without food,” says Angelone. “Eat breakfast so your body doesn’t need to learn how to slow down in order to function properly.”
Eat an anti-inflammatory diet
“Inflammation slows metabolism. Eat a variety of minimally processed and colorful fruits and vegetables to tame inflammation,” says Angelone. “These foods provide many natural plant compounds in addition to many vitamins and minerals which can lower inflammation.” Next up: Can Running Really Help You Lose Belly Fat?
Sources
“Daily energy expenditure through the human life course.” Science. Emily L. Doctor, DNP, nurse practitioner with NYU Langone’s Weight Management Program.Sonya Angelone, MS, RDN, CLT, registered dietitian nutritionist and spokesperson for the Academy of Nutrition and DieteticsDr. Michael Jensen, MD, endocrinologist at Mayo Clinic
