Science behind dieting can aid in weight loss

If sticking to a diet were easy, so many of us wouldn't be so fat.

Everyone knows the formula — eat less, exercise more — but few people follow it. It's not for lack of trying. At any given time, 30 percent of men and 40 percent of women are on a diet.

But every would-be weight loser faces a slew of powerful evolutionary forces designed to thwart even the most determined dieter. Put a new food in front of us, and we'll eat it, even if we felt full minutes earlier. When physical activity starts to burn up calories, a hunger mechanism kicks in, making us eat more. If we start to lose weight, other metabolic processes and brain signals make sure our hunger switch stays on.

"Throughout most of human evolution, we weren't sure where the next meal was going to come from," says Richard D. Mattes, food and nutrition professor at Purdue University. "Hunger is a mechanism to ensure we eat when we find food and that we eat as much of it as we can."

While the strategy worked just fine for the caveman, it's a problem if you live in a world where food is not only plentiful, but supersized. Factor in the various social, cultural and economic pressures to eat, and it seems the average dieter doesn't stand a chance.

So is losing weight impossible? Of course not. People lose weight and keep it off all the time.

Exactly how they do it is rooted in a body of scientific research that teaches us the secrets of a successful diet. Science tells us the types of foods we should eat, as well as the amounts. It tells us how to eat, as well as the ways to monitor our diet. It tells us the little tricks that can make all the difference between success and failure.

One thing is clear: The basic rules don't change. The only way to lose weight is to cut calories. The diet gurus sell a lot of books by making it seem otherwise. But while a given diet plan may tell you to count the carbs or the fat, your body is still counting calories. It doesn't matter if they are carb calories or fat calories or protein calories — your body will shed a pound for every 3,500 calories you cut.

So while popular diets promise sugar-busting, fat-flushing, carb-counting revolutions in weight loss, many of them miss the point. The diet that works isn't based on a single big idea. Instead, it's a set of scientifically based tools that are essential to weight loss — no matter what particular diet you're following.

Stop drinking soda

Over the course of a year, one can of regular cola a day, at 150 calories, adds up to 54,750 calories, or more than 15 pounds.