For a lot of people a new year brings resolutions to lose weight. Here’s some surprising advice at the start of 2008: Don’t go on a diet. Researchers who reviewed dozens of studies on weight loss found that while most people lose weight while on a diet, they don’t keep it off, often gaining more weight than they lost. This cycle of weight loss and gain can cause health problems.

Researchers at the University of California, Los Angeles reviewed 31 long-term studies that followed dieters from two to five years. They found that people typically lose 5 to 10 percent of their body weight in the first six months of a diet. However, between one-third and two-thirds of those studied regained more weight than they lost within four to five years. For example, one study found that five years after dieting 50 percent of participants weighed 11 pounds more than their starting weight.

Researchers caution that the results could actually be worse because many study participants self-reported and those who gained a lot of weight were more likely to downplay their weight gain or not to report at all. In one study of men, those on diets gained more weight than the control group that was not on a diet.

According to the UCLA study, which was published last year in the American Psychologist, repeated weight loss and gain can contribute to stroke, diabetes and cardiovascular disease.

So what’s a better alternative? Maintaining a healthy weight is deceptively simple: Eat less and exercise more. But, it is also extremely complex because our relationship with food goes far beyond hunger. For example, people often eat or starve themselves for psychological reasons. Exercise has also become difficult to work into busy suburban lifestyles.

As a result, millions of people turn to diets to shed pounds. The problem is that without often major changes in lifestyle, diets aren’t enough to help people maintain healthy weights.

The snow piling up outside could offer some incentive. Strap on a pair of cross-country skis or snowshoes and head out into the woods. A half-hour of exercise will help both body and mind. Don’t have that much time? Even a snowball fight with the kids or building a snowman is a good start. If all else fails, shoveling snow counts, too.

Just don’t reward yourself with hot chocolate and leftover Christmas cookies.