Health: Study Shows Why It's Hard to Keep Weight off

For years, studies of obesity have found that soon after fat people lost weight, their metabolism slowed and they experienced hormonal changes that increased their appetites. Scientists hypothesized that these biological changes could explain why most obese dieters quickly gained back much of what they had so painfully lost.

But now a group of Australian researchers have taken those investigations a step further to see if the changes persist over a longer time frame. They recruited healthy people who were either overweight or obese and put them on a highly restricted diet that led them to lose at least 10% of their body weight. They then kept them on a diet to maintain that weight loss. A year later, the researchers found that the participants' metabolism and hormone levels had not returned to the levels before the study started.

Dr. Stephen Bloom, an obesity researcher at Hammersmith Hospital in London, said the study needed to be repeated under more rigorous conditions, but added, It is showing something I believe in deeply — it is very hard to lose weight. And the reason, he said, is that your hormones work against you.

For more, see Study Shows Why It's Hard to Keep Weight off by Gina Kolata, October 26, 2011 at NYTimes.com.