Thirty years later, a new study about exercise emerges that reminds me of what we consider absolute truths may not be so. For as long as I can remember, exercise has been associated with increasing your metabolism. It's been widely believed that exercise contributes to weight loss by burning calories and increasing your metabolism, which is believed to keep revving and burning calories even during the cool down phase. While certain people argued that exercise was not an effective way to lose weight because they were unsuccessful losing weight despite much exercise, it was still a tenet of the weight loss movement. For example, Weight Watchers allows you to add extra "points" based on the amount of exercise you do.
The new study, which is a wonderful study, titled Hunter-Gatherer Energetics and Human Obesity, (http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0040503) studied the Hadza tribe of hunter-gatherers in Tanzania. Strapping members of the tribe with a GPS device and having them swallow so-called doubly labeled water, a liquid in which the normal hydrogen and oxygen molecules have been replaced with versions containing tracers, researchers were able to quantify their levels of physical activity, energy expenditures and metabolic rates. What they discovered is groundbreaking!
The study showed that contrary to popular belief, exercise slows down one's metabolic rate so that calories burned are actually far less than expected. What's amazing is that this is intuitive and yet for so long everyone believed otherwise. Think about it for a moment. If your body doesn't eat for several hours, we think (I'm now officially afraid to say anything for certain any more; well, maybe some things) your metabolic rate slows down as your body tries to conserve energy, as it doesn't know when energy will be replenished. Applying that same principle to exercise, when the body senses a loss of energy consumed by increased activity, it makes sense that it will slow down its burn rate to conserve energy.
This doesn't mean that you aren't burning calories and you can't lose weight by exercising. It simply means that you burn less than you think, which means don't think you can eat a lot more because you had a good exercise session.
By now you couch potatoes are turning to your spouses or friends and smugly telling them you were right all along about exercise. Well not so fast. Exercise is still critical to good heart and brain health. Exercise keeps the heart functioning well and exercise has been shown to be as effective as anti-depressants in treating many cases of mild to moderate depression. But that's not all. Two new studies published online in the Archives of Internal Medicine support the tremendous impact of exercise on lowering the risk of death among diabetic patients, and that weight training may reduce the risk for the disease even without aerobic activity.
Quoting medpagetoday.com, "In a large prospective trial, moderately active patients with diabetes had a lower risk of total mortality compared with those who were completely inactive...according to Diewertje Sluik, MSc, of the German Institute of Human Nutrition in Potsdam, and colleagues. And in a separate prospective study, men who did weight training only at least 150 minutes per week had a 34% lower risk of developing diabetes to begin with ...according to Frank Hu, MD, PhD, of the Harvard School of Public Health in Boston, and colleagues."
I also previously wrote about a study that shows that exercise can return the inflexible blood vessels of pre-diabetics to normal as well.
So while exercise is not the great weight loss panacea it was once thought to be, it is still a critical component of a healthy lifestyle. Keep exercising, but more importantly, if you want to stay slim or lose weight avoid the four whites--white sugar, white flour, white pasta, and white rice. If you watched 60 Minutes this past Sunday, you now know that some scientists view sugar as toxic and cancer causing. Just another good reason to choose whole foods like fruits, vegetables, nuts, beans, and whole grains. And of course, don't forget my favorite, Wild Salmon. Bon appetite!