One thing is certain: The average American waistline is expanding. In fact, it has never been bigger. Federal health surveys show that over the past four decades, the mean waist size for men has grown from 35 inches to 39 inches; for women, from 30 inches to 37 inches. The National Institutes of Health recommends that men with waists measuring 37 inches or greater and women with waists larger than 31.5 inches modify their lifestyles to reduce their waists and resulting health risks. Nearly 39 percent of men and 60 percent of women are carrying too much belly fat.