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Is a common pain reliever safe during pregnancy? Can vaping help you quit smoking? Staying Healthy The truth about metabolism March 30, Print This Page Click to Print. Staying Healthy. Children's Health. Free Healthbeat Signup Get the latest in health news delivered to your inbox! Sign Up. Close Thanks for visiting. By the end of the show, all of the participants had lost dozens of pounds, so they were the perfect study subjects to find out what happens when you lose a dramatic amount of weight in a short period of time.
The researchers took a number of measurements — bodyweight, fat, metabolism, hormones — at both the end of the week competition in and again, six years later, in Though all the contestants lost dozens of pounds through diet and exercise at the end of the show, six years later, their waistlines had largely rebounded.
Thirteen of the 14 contestants in the study put a significant amount of weight back on, and four contestants are even heavier today compared with before they went on the show. But the participants' metabolisms had vastly slowed down through the study period. Their bodies were essentially burning about calories fewer about a meal's worth on average each day than would be expected given their weight.
And this effect lasted six years later, despite the fact that most participants were slowly regaining the weight they lost. Sandra Aamodt, a neuroscientist and author of the forthcoming book Why Diets Make Us Fat , explained this may be the body's way of vigorously defending a certain weight range, called the set point.
Once you gain weight, and keep that weight on for a period of time, the body can get used to its new, larger size. When that weight drops, a bunch of subtle changes kick in — to the hormone levels, the brain — slowing the resting metabolism, and having the effect of increasing hunger and decreasing satiety from food, all in a seeming conspiracy to get the body back up to that set point weight.
In the Biggest Loser study, for example, the researchers found each participant experienced significant reductions in the hormone leptin in their bloodstreams. Leptin is one of the key hormones that regulate hunger in the body. By the end of the Biggest Loser competition, the contestants had almost entirely drained their leptin levels, leaving them hungry all the time. At the six-year mark, their leptin levels rebounded — but only to about 60 percent of their original levels before going on the show.
But not every kind of weight loss in every person results in such devastating metabolic slowdown. For example: That great effect on leptin seen in the Biggest Loser study doesn't seem to happen with surgically induced weight loss.
Indeed, all the researchers I spoke to thought the effects in the B iggest Loser study were particularly extreme, and perhaps not generalizable to most people's experiences. That makes sense, since the study involved only 14 people losing vast amounts of weight on what amounts to a crash diet and exercise program. The Mayo Clinic's Jensen said he hasn't found in his patients as dramatic a slowing of the metabolism in studies where people lose about 20 pounds over four months.
With slow, gradual weight loss, the metabolic rate holds out really well. There are some interesting hypotheses, however. One of the most persistent is an evolutionary explanation. That ability would to some extent increase our ability to survive during periods of undernutrition, and increase our ability to reproduce — genetic survival. Today, the thinking goes, this inability to keep off weight that's been gained is our body defending against periods of undernutrition, even though those are much rarer now.
But not all researchers agree with this so-called "thrifty gene" hypothesis. As epigeneticist John Speakman wrote in a analysis , one issue with the hypothesis is that not everybody in modern society is fat:. We would all have the thrifty alleles, and in modern society we would all be obese. Yet clearly we are not. If famine provided a strong selective force for the spread of thrifty alleles, it is pertinent to ask how so many people managed to avoid inheriting these alleles.
Definitely, incorporate resistance training. It will help build lean muscle mass, which in turn will help your body burn more fat at rest. Eating multiple small meals throughout the day also tends to boost your metabolism. He also says you can experiment with adding particular foods to your diets, like caffeine and red chilis, or items rich in branched chain amino acids this has the best taste.
The first two have a minor effect on the body, but briefly speed up your metabolism. Eating things like egg whites and lean meats can help optimize your metabolism, as well. Finally, he calls the concept of intermittent fasting —an approach where you eat a very low amount of calories for a few days a week or go hours a day without food—a useful way for some men to burn extra fat.
Ready to kickstart your workout routine —and your metabolism—today? Show references Anthanont P, et al. Does basal metabolic rate predict weight gain? The American Journal of Clinical Nutrition. Goldman L, et al. In: Goldman-Cecil Medicine. Philadelphia, Pa. Accessed Aug. Losing weight. Centers for Disease Control and Prevention. Accessed June 7, Lam YY, et al. Indirect calorimetry: An indispensable tool to understand and predict obesity. European Journal of Clinical Nutrition. Bray GA. Etiology and natural history of obesity.
Department of Health and Human Services and U. Department of Agriculture. Department of Health and Human Services. Understanding adult overweight and obesity. Obesity in adults: Role of physical activity and exercise. Obesity for Adults, Prevention and Management of.
Bloomington, Minn. Beware of products promoting miracle weight loss. Food and Drug Administration. Litin SC expert opinion. Mayo Clinic, Rochester, Minn.
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