Metabolism Changes

How Your Metabolism Changes Throughout Your Life – and What It Means For Weight Loss

June 13, 2022

How Your Metabolism Changes Throughout Your Life - It’s a well-known fact that metabolism (the chemical process by which the body converts food into energy for life-sustaining tasks) decreases with age, but a recent study reveals some surprising results.

Before we dive into the details and implications of this information and what it means for weight loss, let’s define a few key terms.

Basal metabolic rate, or BMR, is the minimum amount of energy required to carry out basic processes such as breathing, circulating blood, building and repairing cells, digesting food, and eliminating waste. BMR is calculated based on an individual’s height, weight, age, and sex.

Total energy expenditure, or TEE, is a combination of BMR plus energy used for digesting food (dietary thermogenesis) and other physical activities. For individuals who are mostly sedentary, BMR accounts for about 50 to 70 percent of TEE. Dietary thermogenesis accounts for 10 to 15 percent, and physical activity accounts for the remaining 20 to 30 percent.

What did the study find?

Nearly 6,500 subjects (64 percent were female), who were eight days old to 96 years old from 29 countries around the country participated in the study, which was published in August 2021. During the study, researchers calculated TEE in all subjects using a variety of measurements, models, data sets and adjustments to account for differences in age, sex, body size and reproductive status.

They found that infants in the first month of life expend a similar amount of energy as adults (energy expenditure was adjusted for size). An infant’s expenditure increases rapidly in the first year, before peaking at about nine months, and about 50 percent higher than those of adults.

Children and adolescents ages one to 20 showed a decline in size-adjusted energy expenditures. At 20.5 years, TEE and BMR plateaued and remained stable through age 60, regardless of sex or pregnancy. At that point, TEE and BMR both begin to decline.

What does this tell us?

It has been a commonly held belief that metabolism fluctuates, correlating closely with metabolic activity throughout an individual’s growth and development. Most people believe metabolism is highest in infants, children, and adolescents, and progressively declines in adulthood.

But the results of this study suggest otherwise. So that weight you’ve put on in your middle-aged years? Those pounds cannot be blamed on a slowing metabolism. Of course, there are variations in each individual’s energy expenditure, which can impact weight gain and weight loss, as well as weight management.

While it may be that metabolism actually begins to decline at a much older age than previously thought, the basics of maintaining a healthy body weight have not changed. Diet, exercise, stress level, and rest are all key factors in maintaining a healthy weight and should be carefully managed throughout childhood and adulthood.

So if it’s not a slowing metabolism, what’s causing your weight gain?

There are both mental and biological factors at play that may be causing you to gain weight, or making it difficult to lose weight.

Mental hurdles keeping you from losing weight can include:

  • Poor habits
  • Inability to say “no”
  • Emotional eating
  • High stress levels
  • Not enough or poor sleep
  • An all-or-nothing mindset
  • Shame and defeat

Biologically, there are natural processes in the body that regulate body weight and fat levels. It is a complex system of signals that control hunger, digestion, energy balance, and metabolism. There is such a thing as “set point,” the weight your body is trying to maintain, regardless of changes you make in diet and lifestyle.

Fortunately, we have learned that even people who are obese can reset their body’s set point, ultimately achieving long-term weight loss. One way this can be achieved is through weight loss surgery. Bariatric surgery actually works to recalibrate the body’s set point by altering the production of hormones that stimulate hunger and weight gain.

If you are overweight and struggling to shed those extra pounds, no matter your age, weight loss surgery might be a promising solution. Make an appointment with a qualified weight loss surgeon to learn more about the options and find out if bariatric surgery is an option for you.

Dr. Nick Nicholson practices out of the Nicholson Clinic for Weight Loss Surgery

Metabolism Changes


Dr. Nick Nicholson is one of the nation’s leading bariatric surgeons. He’s been performing weight loss surgery since 2001 and has helped patients from ALL 50 states and 11 countries. He leads a team of top surgeons, specializing in Sleeve Gastrectomy, Gastric Bypass, LAP-BAND, Revisions, Gastric Balloon, and abdominal cosmetic surgery after weight loss. He practices out of the Nicholson Clinic for Weight Loss Surgery. Read more articles by Dr. Nick Nicholson!