There is no such thing as "ideal weight"

I visited my children recently, and listened to my son-in-law proudly showing his thinner body. He is following a healthy plan of eating, specifically McDougall's (rapid weight loss version) and he has lost 20 pounds in two months. He wants to take off another 30 pounds. I did not ask why, but I know his weight loss is health-related. He thinks he will be healthier. But it isn't the fat that makes you unhealthy. It's the fitness level.

1. BMI ratings are meaningless. I don't think I need to flog this horse again but if you are interested Google BMI myths and you'll find enough. Suffice to say the measurement is too simplistic and that no studies back it up as a good predictor of health. It was developed in the 1800s as a convenient quick way to list whether people were heavy or not (I think it was for the army) and it has no scientific basis.

2. Study after study shows that fat people who exercise are as healthy as thin people who exercise. Assuming similar levels of activity. In fact, in studies that actually look at BMI measurements it turns out that the chubbier folks live longer than the really thin folks. Funny, huh?

For more about this topic take a look at An Epidemic of Obesity Myths. Lots of good stuff here. Also take a look at the book The Obesity Myth (different author) and Rethinking Thin.

There is no ideal weight. There is a range of weights that correlate with long lives, but fitness levels are a better indicator.