The latest research shows exercise has little to no effect on the rate of your metabolism

IT

seems straightforward — if you want to boost your metabolism and lose weight, burn calories by moving and exercising more. But the latest research shows exercise has little to no effect on the rate of your metabolism.

Dr. Herman Pontzer, an anthropologist at Duke University, is an expert on human metabolism and energy expenditure. Through his research, he discovered that the average daily expenditure — the amount of calories we burn per day — is the same for everyone, regardless of how much you move.  This means the office worker and the personal trainer both burn the same amount of calories a day, and the amount of time one spends being active has very little to do with the speed of metabolism. Not only is the rate of metabolism the same from person to person regardless of gender, it also remains steady for most of a person’s life. The biggest metabolism drop is at your first birthday, followed by a drop in your twenties. There is a drop again when you hit 60, accompanied by an overall slowdown throughout the body.

Dr. Pontzer’s studies included a wide range of subjects — a modern-day tribe in Tanzania, marathon runners who raced across the US, and people who are sedentary. Study after study showed that active people and sedentary people use the same amount of calories per day.

Before beginning his research, Dr. Pontzer assumed exercise pushes your body into to a calorie deficit, forcing it to burn more calories than you put in. That’s why he chose to study the Tanzanian hunter-gatherers. He assumed that because of the enormous energy they put into their daily activities, they’d be burning thousands of calories a day. However, the research showed otherwise.

The results of his research counter much of what we think about exercise and weight loss. It may also generate questions among those who’ve seen weight loss results after beginning a new fitness routine.

Initially, when you change the intensity of your workout, you may see a change in your weight. But over time, your body makes adjustments to reduce what you burn. For example, say you start a weekly routine where your daily workout burns 500 calories a day. Logically, what would follow is a burn of an extra 3,500 calories per week, resulting in a loss of a pound per week. Instead, what happens is that your body notices the change, and then adjusts to prevent the loss of so many calories. Over time, you’ll notice diminishing returns as your body returns to the baseline metabolic rate.

This is what Dr. Pontzer observed among the marathon runners. The runners ran 26 miles a day from Los Angeles to Washington, DC, over five months. He measured their metabolic levels at three points: prior to beginning the five-month race, a week into the race, and then at the end of the race, a week or two before they reached their final destination. The metabolic rate during the first week of racing rose from pre-race levels as expected. The runners were burning an average of an extra 2,600 calories per day — think 100 calories per mile. But five months later it was below what you’d expect. The runners were burning only an extra 600 calories per day after running 26 miles.

When you think about it, burning an extra 600 calories a day is pretty impressive. But considering the input needed to burn those calories — running a marathon a day — the results are negligible. Also, notice how the bodies of the runners made adjustments so that the initial loss dwindled by 2,000 calories per day.

According to Dr. Pontzer, only the reduction of caloric intake will result in weight loss.

While exercise can’t make you lose weight, it can help control weight in other ways.

A recent study suggested that some exercise could suppress appetite. Researchers focused on ghrelin levels of both men and women before and after exercise. Ghrelin, also known as the hunger hormone, is associated with feelings of hunger. Researchers found that high intensity exercise suppressed ghrelin levels.

Exercise also protects against cardiovascular disease, diabetes, inflammation, and dementia. It’s a mood booster, and has been linked to longevity. So even though exercise won’t kick those extra pounds, it has multiple benefits that make it worth your while.

(Originally featured in Family First, Issue 947)