I think that is probably true with the exception of females whose weight gets low enought that they lose their menses. I think that's our bodies way of telling us "enough is enough!" and is good indicator that weight is too low. Many physicians will use that as a cut-off point for weight loss. I'm not saying that's the case with the OP, of course, since she didn't mention that.

I do think it would feel pretty tricky to work so hard to loose weight and then need to gain a bit back. I imagine I would be a little concerned that I didn't inadvertantly start myself back on the path of gaining too much back!