Your metabolic rate does change during your early life, but it plateaus between the ages of 20 and 60, and only decreases by around 1% per year after that. Your total daily energy expenditure also depends on your weight. So, if your body composition changes, your energy expenditure will also change.
Researchers found that metabolism peaks around age 1, when babies burn calories 50 percent faster than adults, and then gradually declines roughly 3 percent a year until around age 20.
Why Does Metabolism Slow Down as You Age? Loss of muscle mass. As you age, you naturally lose muscle mass. As a result, you burn calories at a lower rate.
Over time, studies have shown that metabolic rate (how fast we burn calories) starts to slow down by 2 to 3 percent each decade, beginning in our 20s. It becomes more noticeable between ages 40 and 60.
Slow metabolic rate contributes to slow pace of aging
According to Herman Pontzer, lead author of the study and anthropologist at Hunter College in New York, the results surprised them: “Humans, chimpanzees, baboons, and other primates expend only half the calories we'd expect for a mammal.
A slow metabolism has many symptoms, and you're likely to have one if you find it difficult to lose weight and easy to gain weight. Other symptoms include fatigue, poor digestion, constipation, low mood, and a colder than average body temperature. All of these are caused by the lower production of energy and heat.
Epidemiologists have observed that the average person typically puts on 1 to 2 pounds a year from early adulthood through middle age. The CDC's numbers show that much of the increase is concentrated in the 20s, for men and women.
Fat-burning ingredients like protein, spicy peppers and green tea have been proven to bump up metabolism. Eat some form of these foods, especially protein, at every meal. Protein is especially important: It takes more calories to digest than other foods and also helps the body build fat-burning lean muscle tissue.
A combination of things happens as we age. We tend to lose muscle mass, so our abdominal muscles aren't as tight as they once were, and the loss of elastin and collagen in our skin allows gravity to have its way so skin starts to sag. Both can cause the waistline to expand.
That is, metabolic rate is thought to be inversely proportional to maximum lifespan, which means that species that live fast will die young while those that have a slower metabolic rate live slower and longer.
“In your 20s, the main culprit to weight gain is stress, which causes high cortisol, one of your body's key fat-storage hormones,” says Dr. Sara Gottfried, bestselling author of “The Hormone Cure” and “The Hormone Reset Diet.” Cortisol, a hormone released in response to stress, can wreak havoc on our bodies, she adds.
B-complex vitamins: These help metabolize carbohydrates, fats, and proteins, activating stored energy instead of letting it turn to fat. Niacin, vitamin B-6, and iron: This impressive trio increases your body's production of the amino acid L-carnitine to help burn fat.
The amount of body fat goes up steadily after age 30. Older people may have almost one third more fat compared to when they were younger. Fat tissue builds up toward the center of the body, including around the internal organs.
The finding of the study suggests that people in middle age certainly gain weight and it is harder for them to lose it, but slow metabolism is not the real reason behind it. It was revealed that from the 20s to the 50s the energy expenditure is the most stable.
“Obesity incidence starts increasing in one's twenties and peaks at 40 to 59, and then decreases slightly after age 60,” says Craig Primack, MD, an obesity medicine physician at the Scottsdale Weight Loss Center in Arizona.
Burn more calories than you eat or drink. Eat more veggies, fruits, whole grains, fish, beans, and low-fat or fat-free dairy; and keep meat and poultry lean. Limit empty calories, like sugars and foods with little or no nutritional value. Avoid fad diets because the results don't last.
Watermelon, cantaloupe, honeydew—these are naturally good for metabolism. Watermelon may even help with weight loss because it contains the amino acid arginine, which was found in a study of obese mice to reduce body fat gains by 64 percent.