HEALTHY BYTE: Metabolism & Aging

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New Study Says That Your Metabolism Doesn’t Really Slow Down until This Age

Stephanie Gravalese; Reviewed by Jessica Ball, M.S., RDAugust 17, 2021·2 min read

We’ve been told over the years that the body’s metabolism (or the rate at which we convert food and drink into energy) is at its peak during our adolescent years. After that, our metabolism reportedly experiences a steep decline through middle age and onward, which makes us process calories at a slower rate and causes that seemingly inevitable midlife weight gain. But a recent study has found that this might not be the case.

Recent findings published in the journal Science show that the peak in our metabolism is actually much earlier, and that the sharp decline does not occur until your 60s.

While metabolism is discussed in reference to the consumption and processing of calories, it impacts much more than your ability to gain or lose weight. Every action in the body (even thinking) requires energy, aka calories, to keep us moving.

“There are lots of physiological changes that come with growing up and getting older,” study co-author Herman Pontzer, Ph.D., associate professor of evolutionary anthropology at Duke University, told Duke Today. “Think puberty, menopause, other phases of life. What’s weird is that the timing of our ‘metabolic life stages’ doesn’t seem to match those typical milestones.”

The research team evaluated calories burned by over 6,600 people in 29 countries, with participants ranging in age from 8 days old to 95 years of age, to determine how much energy was expended each day.

The study suggests that infants (not teenagers) have the highest metabolic rate in relation to their size. Granted, this is partially due to how small infants are and how quickly they grow compared to their body size. This period of increased metabolism is in line with a critical period in early development. At this peak, a 1-year-old child can burn through calories 50% faster than a middle-aged adult. After this peak in energy consumption, the study shows that between the ages of 5 and 20, our our metabolism slows down at a rate of about 3% each year. From our 20s, this metabolic rate remains steady (and does not decline) until our 60s. The study also found that factors like pregnancy and menopause did not contribute to decline in metabolism.

If you’re between the ages of 20 and 60 and feel like your metabolism has slowed down despite this compelling research, fear not. There are a few things you can do to perk up your metabolism at any age, such as eating a healthy diet full of protein and whole foods, incorporating regular strength training, drinking green tea, eating certain spicy foods and cutting off your technology use before bed.

Healthy Byte: ‘Starvation Mode’ the Myth

close-up on a man's stomach as he rubs itCould this man be experiencing starvation mode? | iStock.com

If you eat healthy, count every calorie, keep track of your nutrients, and work out day in and day out, then you’re probably expecting your body to get lean and strong in no time. So, if you find yourself hitting a weight-loss plateau without cheating on your diet or slacking on your exercise routine, you may assume you’ve hit starvation mode. This phenomenon, according to Livestrong, affects anyone who eats below their recommended daily caloric intake and makes weight loss nearly impossible. But is there any truth to this claim? It’s time to dispel myth from reality.

This is what starvation mode in dieting is said to be — a complete halt in weight loss when you’ve gone too far with your extreme dieting. Here’s the truth: While your body will have a response to cutting calories, it won’t be strong enough to completely prevent you from losing weight.

healthy foods and a tape measure

Healthy fresh produce for weight loss | iStock.com

In truth, The Washington Post explains metabolism will slow when you’re cutting calories. This is your body’s natural response to a significant change in your diet and your routine, but this doesn’t happen overnight. In fact, this slowing of your metabolic rate doesn’t even happen within the first six to eight months of extreme dieting, which is when most people find that they hit their first plateau and look toward starvation mode as a reason. It takes years and years of severe calorie restriction for your metabolism to completely offset a reduction in calories.

The idea that you won’t lose weight when your caloric intake is too restricted is completely dispelled when looking at The Minnesota Starvation Experiment outlined by the American Psychological Association. In World War II, men were worked to physical extremes and were given less than 1,600 calories to eat a day, resulting in extreme hunger, gaunt bodies, and malnutrition. They were rehabilitated back to full health by being fed a proper number calories, but nowhere in this study did they find the men stopped losing weight because they were eating too little. In fact, all of the participants lost about 25% of their body weight.

If you’re at the point in your diet where you’re unable to lose weight further, A Workout Routine suggests this may be because your body simply isn’t burning as many calories as it did when you weighed more. When your body weight decreases, you burn fewer calories in general, meaning the diet that worked for you when you were 50 pounds heavier may not be working so well for you anymore.