Previous studies had raised concerns that losing weight might be harmful to older adults, since some research had linked dropping weight to a higher rate of death.

"There's been a little bit of a conundrum on whether it's a wise thing or not to ask an overweight older adult to lose weight."

But if a woman loses a lot of weight, this process shuts down. It's the body's way of preserving what resources it has. If a woman menstruates, she loses iron - and if she has little nutritional input, she can't afford to lose that.