People gain much less weight than commonly believed during the holiday season that stretches from Thanksgiving's pies to New Years' excesses, according to a federal study published Thursday of 195 adults.
But that encouraging word was tempered by another finding: Despite health club come-ons and springtime epidemics of bathing suit dread, the subjects who gained a festive pound or less tended not to lose it over the course of a year, setting themselves up for substantial weight gain or even obesity over the years.
In the study, appearing in the New England Journal of Medicine, researchers weighed the volunteers in the fall, winter and spring. Fifty percent of the subjects gained an average of a pound over that period. Of those, fewer than 10 percent put on five pounds or more, and they tended to be overweight to begin with.
Also somewhat unexpected, given vast holiday complaining about too much punch and too many cheeseballs, 50 percent of the subjects did not gain significant weight. Regular physical activity was largely the reason, say the researchers, based at the National Institutes of Health.
The study, apparently the first to assess seasonal weight gain in a rigorous way, debunks the notion that Americans typically put on five or more pounds over the holidays . Though the researchers cited news reports and press releases that disseminated the figure, they turned up no reliable academic or government study to back it up.
Most important, weight experts said Wednesday, the study sheds new light on the great Mystery of the Expanding Waistline, suggesting that a seemingly negligible seasonal gain can persist. ''That is a core finding and may be important in understanding the continuing weight gain we see in the American population over time,'' said Dr. W. Stewart Agras, a Stanford University psychiatrist specializing in weight disorders.
''Upping one's activity level may be the antidote to this, if a somewhat painful one,'' he added. Indeed, the 45 volunteers who reportedly increased their physical activity over the holidays had the least weight gain. Several actually lost weight.
As previous research has shown, being obese or seriously overweight increases the risks of health problems like cardiovascular disease and diabetes. And preventing weight gain, difficult though it may be, is easier than losing weight, health experts and amateur scale watchers agree.
No one disputes that the six-week holiday season beginning in late November is fraught with metabolic perils. Dropping temperatures and waning daylight threaten exercise routines. Devilish holiday platters tempt. Meanwhile, the basic mammalian drive to store energy as fat for winter's scarcity may kick in.
The health institute study does not pinpoint exactly why some volunteers gained weight. Still, one of the study's six co-authors said it was significant that the volunteers tended not to gain weight in late winter, when the celebrations tapered off. ''It's likely that holiday behaviors such as over-indulging in food and drink did contribute'' to the weight gain, said Dr. Susan Yanovski, executive director of the National Task Force on the Prevention and Treatment of Obesity.
The yearlong study, begun in Sept. 1998, relied primarily on volunteers from the National Institutes of Health in the Washington, D.C., suburb of Bethesda, Md. It employs 19,000 people, groundskeepers to Nobel laureate scientists. The subjects, 18 to 82 years old, largely reflected aspects of the U.S. population: 51 percent were women, 17 percent black, 10 percent Asian, 6 percent Latino.
Nonetheless, some experts suggested that a sample drawn from the world's leading medical research facility might be considerably more health conscious than most Americans. That might have led the researchers to underestimate holiday consequences.
''The findings are encouraging, but I would hesitate to extrapolate from them to the whole population,'' said Dr. C. Wayne Callaway, a physician specializing in nutrition and obesity in Washington, D.C.
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