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    Jan. 4, 2016 -- So you’re finally ready to lose weight. Now the question is: How?

    The standard advice -- to eat less and move more -- isn’t so helpful when it comes to the “how.” You probably know you need to cut calories, but how many? Are you better off getting those calories from low-fat or low-carb foods? And what’s going on with your metabolism, your personal energy-burning furnace? Is it programmed to keep you overweight? Is there any way to fan the flames so you can dream of one day eating a piece of pie without gaining a pound?

    Even science is still stumped on many of the basic questions of weight loss.

    “Amazingly, in this era of obesity, there are still many things that we really don’t know,” says Robin Callister, PhD, professor of human physiology at the University of Newcastle in Australia.

    Here’s what we do know about some of the most persistent mysteries of weight loss.

    Do You Have to Cut 3,500 Calories to Lose a Pound?

    The idea that dieters need to cut this many calories -- with diet, exercise or both -- to lose 1 pound of weight comes from an influential scientific paper published in 1958. Max Wishnofsky, MD, a doctor who lived in Brooklyn, N.Y., tried to sum up everything we knew about how calories are stored by the body. He concluded that when the body is in a steady caloric state -- meaning it isn’t fasting or starving -- extra calories will be stored as fat, and it would take 3,500 extra calories to create a pound of fat. In that same steady state, he also said it would take a deficit of 3,500 calories to lose a pound of weight. For decades, the “Wishnofsky Rule” has been math that determined dieters live by.

    The trouble is that it’s wrong.

    The 3,500-calorie rule doesn’t work because the body adjusts to weight loss. It quickly decreases the number of calories it needs to maintain its new, lighter size, says Corby Martin, PhD, director of the Ingestive Behavior Laboratory at the Pennington Biomedical Research Center in Baton Rouge, LA. That means weight loss slows down over time. People who expect to drop a pound for every 3,500 calories they cut will soon become frustrated when the scale doesn’t cooperate.