Ep. 119: The Truth About Calories And Weight Loss with Dr. Herman Pontzer
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Above, Pontzer is pictured in the metabolic chamber that he uses to determine calorie expenditures for the research subjects in his studies. Photo credit: Justin Cook.
The relationship between diet, exercise and weight loss is more complicated than you think. You know that 500 calories you burned on your morning run? Your body doesn’t just credit you that energy for weight loss. In fact, the work of evolutionary anthropologist and globally recognized metabolism expert Herman Pontzer of Duke University suggests that your body will figure out a way to offset those burned calories after your exercise, possibly by decreasing calorie-burning inflammation in the body. Pontzer’s research suggests that while exercise isn’t a great trigger for weight loss, it remains important for all sorts of wellness reasons. In this encore presentation of Pontzer’s conversation with Medcan’s director of weight management, Dr. David Macklin, the Duke associate professor discusses his most recent book, Burn. Also on the agenda: The fascinating metabolisms of Tanzania’s Hadza tribe of hunter gatherers, and what that all means for North Americans and their sedentary lifestyles.
LINKS
Connect with Pontzer on Twitter, and connect with guest-host Dr. David Macklin on Twitter. Read Pontzer's bio.
Looking for support in your weight loss journey? Visit Medcan’s Weight Management program or book a consultation by calling (416) 350-5918 or emailing weight@medcan.com.
To learn more and support the Hadza community, visit The Hadza Fund, co-founded by Pontzer.
Read this recent study led by Pontzer: Daily energy expenditure through the human life course in Science.org.
New York Times Well Blog article on Pontzer’s research: What We Think We Know About Metabolism May Be Wrong
The New York Times’ Sunday magazine also published an article about Pontzer’s research: The New Science on How We Burn Calories
In the magazine, Science: Evolutionary anthropologist Herman Pontzer busts myths about how humans burn calories—and why
Watch this virtual presentation by Pontzer on his research: How Our Evolutionary Past Shapes Our Health Today
Get your copy of Pontzer’s book, Burn: New Research Blows the Lid Off How We Really Burn Calories, Lose Weight, and Stay Healthy, at Amazon or Indigo.
This 2012 New York Times article, Dieting vs Exercising for Weight Loss, was one of the first to share findings from Pontzer’s ground-breaking research on the Hadza tribe in Tanzania.
In The Exercise Paradox, published in the Scientific American, Pontzer shares his experiences in Tanzania, drawing energy expenditure comparisons not only with the Hadza but with great apes, too.
In this Daily Mail article, Hitting the Gym Won’t Make You Thin, Pontzer explains how active people burn more calories on exercise, but spend less energy on other stuff, such as immune functioning.
In this National Post article, Kids Should Eat Better Because Exercise is a Terrible Tool for Losing Weight, Pontzer compares the calorie expenditure of kids from the foraging and farming Shuar tribe in the Amazon to kids in America and the U.K., to find that the less active kids still burned the same amount of calories. He argues the only way to deal with child obesity is through diet.
INSIGHTS
The body reacts to exercise differently than we tend to believe. When we work out regularly, our bodies end up burning fewer calories on other activities. Dr. Macklin gives a great example: “If I […] burn 300 calories of energy in my workout […] my body's then going to burn about 300 calories less than it was going to, just to make up for that silly thing that I did, trying to increase my daily energy expenditure. And I'm not going to get credited those calories. right?” Pontzer explains: “If we exercise long term, […] our body has time to adjust to it. Well, that adjustment will mean less energy on other stuff. And so the total energy we spend day-to-day is actually not going to be much different than before we started to exercise.” (3:19)
Studies show that we can’t control our metabolic rate. Exercise doesn’t speed it up. If you try to lose weight too quickly with starvation diets, your metabolism will pull back. “The best approach would be to pull back kind of slowly, to not try to lose five pounds a week, or whatever it is. Don’t go too far, too fast,” Pontzer recommends. “You want to find a diet that makes you feel full on fewer calories.” (21:57)
So how can you measure a metabolism over the long term? “It's a really cool technique,” Pontzer explains. “You drink some water that's isotopically tagged. Some of the hydrogens are deuterium, some of the oxygens are oxygen-18—those are just different forms of hydrogen and oxygen; we can use those like tracers. It's totally stable and not toxic or anything like that, it's very safe, we use it all the time,” says Pontzer. He then collects urine samples every few days, to track how and when the body flushes out those isotopes. “And so we get a really accurate measurement of CO-2. You can't make CO-2 without burning calories, you can't burn calories without making CO-2,” he says. (7:04)
Women have similar metabolic rates compared to men. Because women tend to be smaller—on average —than men, and tend to carry less lean muscle mass, their overall calorie expenditure tends to be lower than men’s. “The biggest difference is just size and particularly the amount of lean mass that [women] carry,” Pontzer explains. As a result, it can be more difficult for women to lose weight as quickly as men. (15:45)
When it comes to weight loss, it’s not exercise that determines whether you pack on the pounds or not. It’s diet. “You’ve got to focus on how many calories you bring in. That's going to be where you're going to have the best leverage to try to change and manage your weight,” Pontzer argues. (18:57)
*LEGAL
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