Week of Aug. 23, 2003; Vol. 164, No. 8

Tuesday Can Be Fat, but Weekends Are More Fattening

Ben Harder

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Unsuccessful weight watchers are well aware that the winter holiday season can bestow, besides gifts, a few extra pounds. But according to Barry M. Popkin of the University of North Carolina in Chapel Hill, people seem to approach every weekend as a holiday: They eat and drink too much.

For the average adult in the United States, excessive eating and drinking on Fridays, Saturdays, and Sundays might translate into 5 or 6 pounds (about 2.5 kilograms) of weight gain over the course of a year, says Popkin, who studies nutritional epidemiology.

"Two thirds of Americans are gaining weight, and a lot of that is coming from this extra weekend eating," he says. Typical adults 19 to 50 years old "are eating an extra 115 [kilo]calories a day, and getting a lot of that from fat and alcohol . . . which probably means they're going out drinking, and they're eating a lot of fatty snacks," he says.

On average, Popkin and his colleagues have recently determined, people in that age range get 42 more kilocalories from alcohol and 50 more kilocalories from fat on each weekend day than on Mondays through Thursdays. Protein and carbohydrates account for the remaining 20 percent of excess kilocalories consumed on weekends.

The researchers count Fridays as weekend days because their analysis shows that food and alcohol consumption patterns on Fridays are more similar to those on Saturdays and Sundays than to patterns on other weekdays.

Significant differences in energy intake on weekend days and weekdays also exist for people younger than 19 and older than 70, but people in between account for the most dramatic weekend gorging, Popkin and his colleagues report in the August Obesity Research.

For the study, the researchers tabulated data on what foods more than 14,000 volunteers consumed on each of two days of the week, and mathematically filtered out influences from factors such as income, education, ethnicity, and where each volunteer lived. The scientists got their data from a nutritional database that represents all U.S. residents over the age of 2 years.

It's not certain that extra weekend energy intake translates into weight gain, because the study didn't examine whether physical activity varied with the day of the week. "We really don't know much about physical activity on weekends versus weekdays," Popkin acknowledges. But if additional calories aren't burned as quickly as they're consumed on weekends, then off-day indulgences are contributing to people's girth, he says.

The lesson is that behavioral patterns that might contribute to excess weekend eating and drinking need to be addressed in weight-loss clinics and other settings where people are struggling to maintain or lose weight, Popkin says. He contends that addressing excessive weekend eating is more important to the battle against obesity than is preaching moderation during the holidays or any particular season.

Seasonal variations in calorie intake, he says, "just don't seem to have the same public health meaning" as day-of-the-week influences do. Adults 19 to 50 years old, for instance, eat an average of 62 more calories per day during the fall than in other seasons. But that seasonal effect doesn't hold for all age groups: 51-to-70-year-olds eat more during the spring and summer than they do during the rest of the year.

Lightweights. I had a bad food week last week, and put on five pounds.