Janice Bridge before losing 165 pounds. Husband Adam lost 110 pounds—2001

Ahh the joys of the holiday season: food, fun, drinking, friends, family…and lots of stuffing and desserts and cookies and Christmas candy. Sometimes I eat three or four different slices of cake and pies at a time—very thin slices, of course. And with all the company in the house and tennis buddies taking off for warm climes or out-of-state relatives, my tennis games—and all that calorie-burning cardio—evaporate. So I gain my usual 3-5 pounds in a week.

But this year I had already put on five pounds to not look too thin and gaunt and old. So when the scale started to approach 180 pounds, up from 170 a few months ago, I freaked out. That’s just over the top for me. As soon as the visitors let up, I stopped eating those desserts and all the carbohydrates. And the pounds are starting to melt away. I am down to 175-176 again. A real relief.

Then I read this long article in the New York Times by Tara Parker-Pope that describes really fat people who might lose weight, but then regain it all back over time. It suggests from a very limited study of just 34 obese people that their bodies just want to be fat, and almost nothing can prevent it. It’s in their genes. So they have a great and rational excuse…if they want to use it.

But a few have been able to keep off the shed pounds…through intense calorie-counting, hours of daily exercise 5-6 days a week, and defying their body’s constant craving for, and focus on, food. Here are some excerpts.

Anyone who has ever dieted knows that lost pounds often return, and most of us assume the reason is a lack of discipline or a failure of willpower.

The Bridges after weight loss—12/2011

For years, the advice to the overweight and obese has been that we simply need to eat less and exercise more. While there is truth to this guidance, it fails to take into account that the human body continues to fight against weight loss long after dieting has stopped. This translates into a sobering reality: once we become fat, most of us, despite our best efforts, will probably stay fat.

The National Weight Control Registry tracks 10,000 people who have lost weight and have kept it off…Anyone who has lost 30 pounds and kept it off for at least a year is eligible to join the study, though the average member has lost 70 pounds and remained at that weight for six years.

Wing says that she agrees that physiological changes probably do occur that make permanent weight loss difficult, but she says the larger problem is environmental, and that people struggle to keep weight off because they are surrounded by food, inundated with food messages and constantly presented with opportunities to eat. “We live in an environment with food cues all the time,” Wing says. “We’ve taught ourselves over the years that one of the ways to reward yourself is with food. It’s hard to change the environment and the behavior.”

There is no consistent pattern to how people in the registry lost weight — some did it on Weight Watchers, others with Jenny Craig, some by cutting carbs on the Atkins diet and a very small number lost weight through surgery. But their eating and exercise habits appear to reflect what researchers find in the lab: to lose weight and keep it off, a person must eat fewer calories and exercise far more than a person who maintains the same weight naturally.

“After you’ve lost weight, your brain has a greater emotional response to food,” Rosenbaum says. “You want it more, but the areas of the brain involved in restraint are less active.” Combine that with a body that is now burning fewer calories than expected, he says, “and you’ve created the perfect storm for weight regain.” How long this state lasts isn’t known, but preliminary research at Columbia suggests that for as many as six years after weight loss, the body continues to defend the old, higher weight by burning off far fewer calories than would be expected. The problem could persist indefinitely.

Janice Bridge, a registry member who has successfully maintained a 135-pound weight loss for about five years, is a perfect example. “It’s one of the hardest things there is,” she says. “It’s something that has to be focused on every minute. I’m not always thinking about food, but I am always aware of food.”

Scientists are still learning why a weight-reduced body behaves so differently from a similar-size body that has not dieted. A result is that after losing weight, your muscles burn 20 to 25 percent fewer calories during everyday activity and moderate aerobic exercise than those of a person who is naturally at the same weight. That means a dieter who thinks she is burning 200 calories during a brisk half-hour walk is probably using closer to 150 to 160 calories.

Nobody wants to be fat. In most modern cultures, even if you are healthy, to be fat is to be perceived as weak-willed and lazy. It’s also just embarrassing.

One question many researchers think about is whether losing weight more slowly would make it more sustainable than the fast weight loss often used in scientific studies. Leibel says the pace of weight loss is unlikely to make a difference, because the body’s warning system is based solely on how much fat a person loses, not how quickly he or she loses it.

So where does that leave a person who wants to lose a sizable amount of weight? Weight-loss scientists say they believe that once more people understand the genetic and biological challenges of keeping weight off, doctors and patients will approach weight loss more realistically and more compassionately. At the very least, the science may compel people who are already overweight to work harder to make sure they don’t put on additional pounds. Some people, upon learning how hard permanent weight loss can be, may give up entirely and return to overeating. Others may decide to accept themselves at their current weight and try to boost their fitness and overall health rather than changing the number on the scale.