Even if you do meet your goal, it's nearly impossible to keep off the weight over the long term: "The amount of restriction required [to maintain that number] will make you so hungry that you’ll eat everything in sight—it’s survival instinct," Dr. Seltzer says. And since calorie restriction gradually slows your metabolism, your body will be less prepared to burn the foods you binge on, he adds. That could mean gaining more pounds than you lost in the first place.
A recent study in the journal Nature found that mice who were fed a breakfast in which 45 percent of the calories came from fat tended to burn more body fat over the next 24 hours than those who ate a meal that was only 20 percent fat. This is early research—it needs to be repeated in humans—but mono and polyunsaturated fats like those found in avocados and nuts do have plenty of health benefits when you eat them in moderation.
Obviously, it’s still possible to lose weight on any diet – just eat fewer calories than you burn, right? The problem with this simplistic advice is that it ignores the elephant in the room: Hunger. Most people don’t like to “just eat less”, i.e. being hungry forever. That’s dieting for masochists. Sooner or later, a normal person will give up and eat, hence the prevalence of “yo-yo dieting”.

At its core, burning fat comes down to the process of lipolysis—the breaking down of fat lipids, explains Seedman. This happens in the mitochondria of the muscles, or the powerhouses of the cells, responsible for generating the energy our cells need to do their jobs. Exercise has been shown to improve mitochondria function, which then promotes fat breakdown, Seedman adds. Plus, working out helps regulate pretty much all the hormones that optimize fat loss.
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