Our weights may be naturally fixed within a 10-20 pound range. While it's possible to use diet and exercise to move above or below that range, it's really really hard. This doesn't surprise me too much based on my own experience (my own weight doesn't vary more than 20 pounds outside of pregnancy, though over the past couple years it has responded more to winter lethargy/ junk food) but it defies most of our cultural assumptions about fat. (via Shapely Prose)