Americans give significant weight to dieting. Some 52 million people (more than a quarter of U.S. adults) say they are on a diet, according to Simmons Market Research Bureau's National Consumer Survey. While two-thirds (66 percent) of those say they're on a diet to shed pounds, 18 percent are simply trying not to gain any more. Women lead the battle of the bulge: They are 75 percent more likely than men to curb their caloric intake. Perhaps surprisingly, 35 percent of the over-18 set contend that they exercise regularly. Sixty percent of the nation's adults acknowledge that they need more exercise.