Though the thought of counting calories and measuring portions doesn't bring smiles to most people's faces, many people succumb to such dieting measures because they believe it will improve their health.

But, according to a two-year study published in the June 2005 issue of the Journal of the American Dietetic Association, if you're looking to achieve long-term health improvements, behavior changes and self-acceptance are more effective than dieting any day of the week.

"We have been ingrained to think that large people can only make improvements in their health if they diet and slim down," said one of the study's researchers, Linda Bacon, "But this study tells us that you can make significant improvements in both metabolic and psychological health without ever stepping on the scales or counting calories. You can relax about food and eat what you want."

The study found a definite relationship between a woman's immune function and her dieting history -- the more times she attempted to lose weight, the more her immune function decreased.

Frequent weight loss and gain may influence a hormone called leptin that influences appetite and eating behavior. It's thought that this effect may explain why women with a history of yo-yo dieting tend to have higher percentages of body fat.