Why even the most resolute dieters fail - STLtoday.com
If you've been trying for years to lose unwanted pounds and keep them off, unrealistic goals may be the reason you've failed. It turns out that a long-used rule of weight loss — reduce 3,500 calories (or burn an extra 3,500) to lose one pound of body fat — is incorrect and can ultimately doom determined dieters.
That is the conclusion reached by Dr. Kevin D. Hall and his colleagues at the National Institute of Diabetes and Digestive and Kidney Diseases. Recently they created a more realistic model of how the body responds to changes in caloric intake and expenditure, basing their calculations on how people of different weights responded to caloric changes in a controlled setting like a metabolic unit.
Their work, spelled out in a new study published in The Lancet, explains how body weight can slowly rise even when people have not changed their eating and exercise habits.
Their research also helps to explain why some people can lose weight faster than others, even when all are eating the same foods and doing the same exercise, and why achieving permanent weight loss is so challenging for so many.
The model shows that lasting weight loss takes a long time to achieve and suggests that more effective weight loss programs might be undertaken in two phases: a temporary, more aggressive change in behavior at first, followed by a second phase of a more relaxed but permanent behavioral change that can prevent the weight regain that afflicts so many dieters despite their best intentions.
DEBUNKING A LONG-USED RULE
According to the researchers, it is easy to gain weight unwittingly from a very small imbalance in the number of calories consumed over calories used. Just 10 extra calories a day is all it takes to raise the body weight of the average person by 20 pounds in 30 years, the authors wrote.
Furthermore, the same increase in calories will result in more pounds gained by a heavier person than by a lean one — and a greater proportion of the weight gained by the heavier person will be body fat. This happens because lean tissue (muscles, bones and organs) uses more calories than the same weight of fat.
In an interview, Hall said the longstanding assumption that cutting 3,500 calories will produce a one-pound weight loss indefinitely is inaccurate and can produce discouraging results both for dieters and for policy changes like the proposed tax on sugar-sweetened beverages.
If the 3,500-calorie rule applied consistently in real life, it would result in twice the weight loss that the new model predicts, the authors wrote. This helps to explain why even the most diligent dieters often fail to reach weight loss goals that were based on the old rule.
A more realistic result, he said, is that cutting out 250 calories a day — the amount in a small bar or chocolate or half a cup of premium ice cream — would lead to a weight loss of about 25 pounds over three years, with half that loss occurring the first year.
Many people get discouraged when weight loss slows even though they are sticking religiously to their diets, but Hall said a gradual loss is nearly always more effective because it allows the new eating and exercise habits to become a lasting lifestyle.
Still, obese people would have to cut out more calories to lose weight than it took to gain the extra pounds. Although reaching a weight of 220 pounds may have been caused by consuming, say, 250 calories more than were used each day, losing that weight requires much larger reductions in calorie intake. According to Hall's calculations, an extra 220 calories a day are now maintaining the new higher weight.
For the population to return to average body weights of the 1970s, obese individuals, who now represent 14 percent of the population, would have to cut out more than 500 calories a day, the new model shows.
Hall noted that typical weight-loss programs result in significant losses over a period of six to eight months, followed by gradual weight regain in the years that follow. When weight-loss plateaus at six to eight months — "which happens with all the diets," he said — many dieters unconsciously start to eat a little more.
Although consuming an extra 100 calories a day would not show up right away as weight gain, it does over time. And it happens more slowly for the obese person than for someone who is lean, Hall said, because the obese person's body requires more calories to maintain the extra pounds.
ROLE OF PHYSICAL ACTIVITY
It is often said that increasing one's physical activity does not have much, if any, effect on weight loss. But Hall's model suggests otherwise.
If a man weighing 220 pounds ran an additional 12.5 miles a week at a moderate pace, he would lose more weight, and slightly faster, than if he cut the equivalent amount of calories from his diet, the authors calculated.
However, as activity and calorie reduction are increased, there comes a point at which the weight-loss benefit of diet exceeds that of physical activity, said the researchers, "because the energy expenditure of added physical activity is proportional to body weight itself."
In other words, heavier people burn more calories in an equivalent amount of exercise; but as their weight drops, the number of calories used in exercise does, too.
The authors warned that when some people increase their level of physical activity, they compensate by eating more. Then, discouraged by a lack of progress, they may cut back on physical activity and gain even more weight.
Nonetheless, Hall said, physical activity remains important to weight loss and especially to weight maintenance. Studies of the more than 5,000 participants in the National Weight Control Registry have shown that those who lost a significant amount of weight and kept it off for many years relied primarily on two tactics: continuing physical activity and regular checks on body weight.
Some studies have indicated that low-carbohydrate diets that are relatively high in protein and fat are more effective for losing weight than a more balanced low-calorie diet. Hall said that while low-carbohydrate diets do a little more to reduce weight over the course of six months to a year, it remains to be shown that people are really eating what they say they are eating in these studies and that they can stick to a low-carbohydrate diet indefinitely.
Hall and his colleagues wrote that "all reduced-energy diets have a similar effect on body-fat loss in the short run" and that 'some diets can lead to reduced hunger, improved satiety, and better overall diet adherence during a weight management intervention."
But they added a caveat: Little is known about the long-term effect of diets that vary in their makeup of fat, protein and carbohydrate on either weight maintenance or health.
22 Sep, 2011--
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