Recent public appearances show that actor Jonah Hill has regained most of the weight he lost while on his well-publicized diet. So does dieting itself make you fat? Or are people genetically predisposed to be fat simply more likely to diet?
It's the dieting, according to researchers in Finland. They found that identical twins who attempt to lose weight tend to end up heavier than their non-dieting siblings who have identical genes.
Why? The researchers offer three possible explanations.
First, dieting may lead to a preoccupation with food, which leads to overeating. Second, dieting tends to slow the metabolism and burn up muscle mass, two changes that hamper the body's ability to burn calories. Finally, weight gain leads to more dieting, and multiple attempts at weight loss compound the two problems just mentioned.
So the old joke -- if you want to gain 25 pounds, lose 20 -- appears to have scientific backing. How can overweight people lose weight without gaining back even more?
Dr. Kirsi Pietilainen, the lead author of the study, suggests losing weight slowly so the body doesn't think it's starving, and exercising more to discourage the loss of muscle mass (and, of course, to burn calories).
"Also, fill up the stomach with low-energy foods," Pietilainen said by phone from Helsinki. "You can do that with vegetables and fruits. And eat protein because that creates more satiety than carbohydrates."
Perhaps the most important strategy involves abandoning diets altogether and adopting instead a new lifelong pattern of eating that does not contribute to weight gain.
"With my patients, we try to find a way to permanently adopt a diet they like, a diet they will be able to continue for the rest of their lives," Pietilainen said. "If you can learn to love vegetables, fruit, low-fat dairy products, fish, meat -- that sort of thing -- and if you exercise more, then you will find a permanent way (to control your weight)."
Another helpful strategy involves mindful eating, promoted by Brian Wansink, a professor of nutritional science at Cornell University and author of "Mindless Eating," a book Pietilainen recommends to her patients even though it is written in English.
"We do exercises in group meetings that help them to eat mindfully," she said. "We concentrate on how the food tastes, smells, feels in the mouth. This is very useful for my patients. A lot of times eating is mindless. You just grab something and don't even think about calories. (At the end of the day) you don't even know how much you've eaten."
Pietilainen said that about 80 percent of her patients can maintain a 5 percent weight loss if they remain in contact with her to receive advice and support, but about 80 percent regain the weight if they don't.
"Many obesity centers have the same results," she said. "If they give patients a regimen to follow and keep in contact with them, they achieve pretty good results, but if patients don't show up, then a year later they have regained all of the weight or more. It's a constant struggle, my patients say, and they need continuous support."