BMI has, and rightly so, many critics. For the average guy, it's still much simpler--anything more than an "inch of pinch" around the waist line--measured at the belly button is too much, and since fat also takes up residence inside the abdominal cavity, if your waist line is larger than your shoulder measurement, you need to work out and diet. Just remember, working out will increase muscle and muscle weighs a lot more per measured unit than fat, so your weight may stay the same--it's the measurements that count.