According to Dr Fuhrman
Men shouldn’t be able to pinch more than a half-inch of skin near the belly button. Women should not be able to pinch more than an inch.
If you have gained as little as ten pounds since you were 18 or 20 years old, then you could have a significantly increased risk for health problems like heart disease, diabetes, and high blood pressure.
I don’t know that I would get too idealistic about this at becuase if you haven’t guessed, weight fluctuates!
Especially as your body get’s more efficient and healthy; you can get inactive for only a few days and even eat Nutrient Rich and put on a few pounds, becuase contrary to the points made in in this Reuters articles on emotional eating, people do eat for emotional, societal and environment reasons, so even eating healthy, you will live "at or near" your ideal weight, rarely at your "ideal weight".
But I still agree Dr Fuhrman, pinch yourself, it’s a good measure!, BMI, if you have a heavily muscled body, can be very misleading and most other methods are just too darn complicated.