Short answers to hard questions about weight loss

Rachel Frederickson competes during the first episode of "The Biggest Loser." Fredrickson lost nearly 60 percent of her body weight to win the latest season of the show. –AP Photo / NBC / Trae Patton

Almost everyone who has ever dieted knows how hard it is to keep the weight off. And almost everyone, including many scientists, has wondered what works. An article Monday about what happened to contestants from “The Biggest Loser” TV show is a vivid illustration of the problem. Although there is no magic formula for weight maintenance, here are answers to some questions that arise over and over.

Are you more likely to maintain weight loss if you lose weight slowly?

That is the advice dieters often get, but studies have not found that to be the case. For example, a recent Australian study, funded by the Australian National Health and Medical Research Council and the Sir Edward Dunlop Medical Research Foundation, randomly assigned 204 obese people to subsist on just 450 to 800 calories a day for 12 weeks, or to cut a more modest 400 to 500 calories a day from their diets over 36 weeks. The goal for both groups was a 15 percent weight loss. Three years after the study began, almost everyone had regained the weight they lost, despite counseling on diet and exercise. There was also no difference in levels of two hormones, leptin and ghrelin, that drive hunger. The main difference between the groups was that more people in the rapid weight loss group lost at least 12.5 percent of their weight (80 percent as compared with 50 percent in the slow loss group) and fewer dropped out (3 percent as compared with 18 percent).

To maintain weight loss, should you avoid snacks?


Although it seems to make sense that snacks can pack on the pounds, studies that randomly assigned people to snack or not have failed to confirm this and even observational studies have not found evidence that snacks undermine weight loss.

If you build muscle with exercise, including weightlifting, will you be able to maintain a higher metabolism?

Muscle burns more calories than fat, so it might stand to reason that the more muscle you have the faster you will burn calories. But it turns out that building muscles has almost no effect on resting metabolism, which determines how many calories a person burns when at rest. The reason is that any muscle you add is small compared with the total amount of skeletal muscle on your body. And most of the time that muscle is at rest. (You can’t go around flexing your biceps nonstop.) Muscles have a very low metabolic rate at rest. One researcher calculated that if a man weighing about 175 pounds lifts weights and puts on about 4 1/2 pounds of muscle — a typical amount for men who lift weights for 12 weeks — he will burn an extra 24 calories a day, the amount in a couple of Life Saver candies.

Can you defeat your body’s slowed metabolism after weight loss by doing vigorous cardiovascular exercise?

The answer is that you can as long as you do not eat more calories to make up for the ones you burned. It sounds simple enough but, says Dr. Michael Rosenbaum, a doctor and obesity researcher at Columbia University, “this is not as easy a proposition as it sounds.” The brain controls how hungry you are and your cravings for food, and it is all too easy to accidentally eat more calories than you burned exercising. That is a major reason studies that use exercise alone to help people lose weight have generally failed to find an effect.


Exercise also has an unexpected effect, documented by Rosenbaum and Dr. Rudolph Leibel at Columbia University. They found that after you lose 10 percent or more of your weight by diet alone, your muscles start using genes that make them more efficient. They burn 20 to 30 percent fewer calories for the same exercise.

Is there a type of diet that helps keep weight off?

Many people swear by diets that are low in carbohydrates or gluten-free or revolve around fasting two days out of seven. Dr. Lee Kaplan, an obesity researcher at Harvard, says that there is no diet or weight loss regimen that is guaranteed to work but that often people can maintain a loss of 5 percent of their weight, which is enough for health benefits to kick in. He tells his patients to try one weight loss program after another in the hopes that they will find something that works for them.

So what hope is there for weight maintenance?

Anecdotal reports by people who have succeeded in keeping weight off tend to have a common theme: constant vigilance, keeping close track of weight, controlling what food is eaten and how much (often by weighing and measuring food), exercising often, putting up with hunger and resisting cravings to the best of their ability. Those who maintain a modest weight loss often report less of a struggle than those trying to keep off large amounts of weight.

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