Why do people regain weight easily after crash dieting?

If you’ve ever launched yourself into a diet regime that severely restricts calories, you may have lost pounds in the short term.

But did you stay at that reduced weight for the long haul, or did the scales start to creep back up again over time?

If it’s the latter, then you are not alone.

A 2007 review in American Psychologistof 31 studies found that at least one-third to two-thirds of dieters regained more weight within a few years than they had originally lost on their diets.

“It appears that dieters who manage to sustain a weight loss are the rare exception, rather than the rule,” write the researchers, from the University of California, Los Angeles.

“Dieters who gain back more weight than they lost may very well be the norm, rather than an unlucky minority.”

Why would the body pile on the pounds so readily after the initial loss?

One possible factor is that the levels of hormones involved in regulating weight can remain changed for long after the diet.

A recent study in Australia asked 50 overweight or obese people to go on a 10-week low-energy diet and looked at hormonal changes before, just after and in the longer term.

"One year after initial weight reduction, levels of the circulating mediators of appetite that encourage weight regain after diet-induced weight loss do not revert to the levels recorded before weight loss," wrote the researchers in the New England Journal of Medicinelast year.

A better bet might be to lose weight slowly.