Science / Medicine : Food for Debate: ‘Yo-Yo Dieting’ : Health: New research finds that a gain-lose-gain weight pattern appears to increase the risk of heart disease. It rekindles the discussions among health experts about how--and if--a person should shed pounds.
In the wake of a major study published last week, it appears that “yo-yo dieters,” caught up in a gain-lose-gain pattern, may have more to worry about than frustration or appearance. Their weight cycling increases their risk of heart disease, researchers reported in the New England Journal of Medicine.
The finding has rekindled debate among health experts about how, and if, a person should go about losing weight. At least one possible implication is that some people might be better off being somewhat overweight rather than repeatedly dieting and regaining weight.
Exactly how weight fluctuation drives up heart disease risk is not certain. Yale University psychologist Kelly Brownell, the study’s lead author, speculates that chronic dieters develop a preference for dietary fat, and that their high-fat diets lead to increased heart disease risk. Also, they may regain weight mostly on the upper body, where excess fat is associated with higher heart disease risk. The researchers do not know how many pounds of weight fluctuation constitute a hazard.
Not everyone is convinced of the link, and the New England Journal of Medicine report is not the first to discuss it. In 1989, a study of 2,000 men published in the American Journal of Epidemiology found that weight fluctuations during young adulthood increased heart disease risk in middle age.
Brownell said the current study is the most dramatic evidence that chronic dieting is hazardous. It is based on evaluations of more than 3,000 men and women from the Framingham Heart Study. The strongest link between chronic dieting and heart disease risk was found in dieters 30 to 44--the people Brownell said are most likely to diet. Overall, chronic dieting was found to raise the risk of heart disease from 25% to 100%, he said.
The next logical step for chronic dieters? Reduce to an ideal weight and stay there, Brownell said, or pick a weight that is reasonable--even if it is above the ideal--and stay there.
Being just a bit too hefty may be healthier in the long run, Brownell said, than gaining and losing the same weight over and over. “Small but frequent cycles may be as bad as many large cycles,” he said.
“Some of the risk is in people who don’t need to be dieting in the first place,” Brownell said. “If they can live with a reasonable--as opposed to ideal body shape--they may be better off staying at a stable weight.”
Maintaining weight loss is easier said than done, as statistics show and lifelong dieters know. About 50% of American women and 25% of American men are dieting at any given time; 95% of dieters regain some or all of the weight.
No one has a foolproof blueprint for maintaining weight loss. Recently, researchers zeroing in on what makes a dieter successful over time have unearthed some surprising findings about exercise, post-diet biochemical abnormalities and the need for “diet readiness.”
Exercise is beneficial, experts agree, both for those trying to lose weight and those trying to keep off the weight they have shed. Now, some researchers say the role of exercise is greater during weight maintenance than during weight loss.
“Exercise has at best a modest effect on weight loss,” said Dr. Stephen Phinney, an assistant professor of internal medicine and director of clinical nutrition and metabolism at the UC Davis School of Medicine who has researched the subject. “It helps most in weight maintenance.”
This is borne out in a study published last year in the International Journal of Obesity by a Netherlands research team that followed up dieters for eight to 12 months. Some dieters lost weight just by calorie restriction; others by calorie restriction plus exercise. The exercising dieters lost more weight and more body fat than the dieters who did not exercise. The exercisers also kept off more pounds over time. On average, they gained back 60% of their initial loss; the diet-only group regained 90%.
In another study, Stanford University researchers compared 121 sedentary, overweight men randomly assigned to a control group, a calorie restriction group or an exercise group. Both the exercise and calorie restriction groups achieved weight loss at the end of one year. But the non-exercising group had a small decline in metabolic rate, leading to the need to restrict calories even more to maintain weight loss. The exercising men had no change in their metabolic rate.
When it comes to reducing heart disease risk, it is critical that the exercise be regular, a Washington University research team found. Abandoning your exercise routine for as little as three weeks can raise your risk of coronary artery disease, said Rick Seip, one of the researchers. The researchers tested blood levels of fats before and after detraining. Lack of exercise resulted in increases in several lipids, including one strongly associated with premature coronary artery disease and stroke.
So is it just as dangerous to stop and start an exercise routine as to bounce up and down on the scale? Researchers say they just do not know the answer.
That is not the only area of mystery for researchers. They are also investigating what happens when people get hooked on exercise and work out vigorously and often.
In an unpublished study of eight women runners who averaged 27 miles a week, Gail Butterfield, a research scientist at the Palo Alto Veterans Affairs Medical Center, found that they maintained body weight over a two-month period on 1,900 calories a day, fewer than might be expected given their energy expenditure. When she compared their calorie intake to that of sedentary women, she did not find much difference. Their average daily calorie intake was also about 1,900. “It may be you can maintain a stable body weight on a variety of different (exercise) regimens,” Butterfield said.
Not wishing to discourage healthy people from engaging in vigorous exercise, Butterfield tells them to think of exercise as more than a calorie-burning activity. Exercise often improves the sense of well-being and helps to maintain the proper ratio of muscle to fat.
Meanwhile, other researchers warn that formerly obese people--even those who have maintained their weight loss--cannot consider themselves on a biochemical par with people born svelte. “Just because you have lost the weight doesn’t mean you are normal,” said Phinney of UC Davis. “A biochemical abnormality may persist even after weight loss,” said Phinney, who studied 25 formerly obese people for two to five months after they shed weight.
In most, he found lower than normal levels of arachidonic acid, a type of fat found in the bloodstream, before and after weight loss. In animal studies, low levels of this blood fat have been associated with genetic obesity, he said, and in humans it is associated with obesity and Type I diabetes. “But beyond that, we don’t know if it’s dangerous or not.”
Regardless of how much weight a person has lost, Yale’s Brownell said to lose weight and keep it off, dieters must identify their personal triggers to overeating, whether it is boredom, the smell of food, depression or other factors.
To maintain weight loss, nonathletic types need to define exercise differently, he said, to consider even a walk around the mall as exercise.
Most important, people who decide to lose weight must be truly ready, Brownell said. If you’re not ready, he said, it may be healthier to postpone the diet or forget it altogether. “One way not to regain weight is not to lose it in the first place,” he said. “As silly as it sounds, that may actually be a better course (temporarily).”
Brownell’s viewpoints are not shared by all his colleagues. Among his critics is Dr. Jules Hirsch of the Laboratory of Human Behavior and Metabolism at Rockefeller University, New York. He said he worries that the recent New England Journal report will discourage overweight people from trying to shed pounds, that the study will be interpreted as “another nail in the coffin of weight reduction.”
Hirsch asked: “Who are these (chronic) dieters (from the Framingham Study)? Perhaps those with a family history of heart disease or beginning symptoms like chest pain.” Those people, he said, are probably more motivated to diet.
On at least one point, Hirsch and Brownell concur: More research is needed about the effects of weight fluctuation. In his ongoing study, Brownell hopes next to pinpoint the minimum fluctuation in weight that might be tied to increased heart disease risk.
Meanwhile, he said, “Dieting should be taken seriously. It’s possible that dieting under some circumstances could creative negative effects.”
