Understand Your Metabolism

People talk about their metabolism a lot. You'd think they actually understand it. 

But often that's not the case. Here are 4 things you should know about the M-word. 

BURNING TRUTH #1: SKINNY PEOPLE HAVE FAST METABOLISMS

VERDICT: Sometimes
"There are slim people with slightly low metabolisms who just don't eat very much," says Michael Jensen, M.D., an endocrinologist with the Mayo Clinic. "And there are heavy people with really high metabolisms who eat a huge amount."

BURNING TRUTH #2: LEAN TISSUE BURNS MORE CALORIES THAN FAT DOES, EVEN WHILE YOU'RE ASLEEP

VERDICT: True
"Your brain, heart, liver, and kidneys use a lot of energy, even when you're lying still," says Dr. Jensen. Muscle and the GI tract don't use much at rest; fat burns practically nothing. His estimate: You burn about a calorie per minute at rest. A quarter of that is torched by muscle, and 1/50th of it is burned by fat.

BURNING TRUTH #3: SOME GUYS CAN ONLY SLIM DOWN BY SLASHING CALORIES

VERDICT: False
"In 30 years I've never seen anyone with a truly low metabolic rate," says Dr. Jensen. "People who think they need an 800-calorie diet often have resting metabolic rates of 1,500 calories." So why can't they slim down? They're often eating many more calories than they realize. His fix: Accurately record everything you eat for two weeks. Unhealthy trends may emerge.

BURNING TRUTH #4: CUTTING 500 CALORIES A DAY MEANS YOU'LL LOSE A POUND A WEEK

VERDICT: Not Quite
A pound of fat does equal 3,500 calories, and you may lose a pound the first week. "But when you eat less, you lose lean tissue, so your basal metabolic rate goes down," says Dr. Jensen. Surprise: You may gain more than a pound after a 3,500-calorie pig-out, since calories stored as sugar cause you to retain water.

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