Men whose jobs keep them behind a desk may need to work harder to keep excess pounds at bay, according to a new report.

In a study of nearly 1,600 Australian adults, researchers found that men who spent most of the workday sitting were almost twice as likely as those with active jobs to be overweight.

What’s more, men with sedentary jobs tended to be heavier even if they got a moderate amount of exercise outside of work.

The same pattern was not, however, seen among women, according to findings published in the August issue of the American Journal of Preventive Medicine.

Although a couch potato lifestyle may promote weight gain, studies have found that changes over time in people’s leisure-time activity do not seem to account for the rise of obesity in many Western countries. Decreasing work activity, according to the authors of the new study, may be a less-noted factor.

“Essentially we are trying to point out the loss of incidental activity relating to sedentary employment,” said Dr. Kerry Mummery, the study’s lead author.

There needs to be greater awareness of the “potential health costs” of such work, said Mummery, of Central Queensland University in Rockhampton.

For their study, Mummery and his colleagues surveyed 1,579 full-time workers about their on-the-job and leisure-time activity levels, and collected information on weight and height for each.

Many men were overweight, regardless of their job description; 52 percent of those who spent little time sitting - less than 45 minutes a day - were overweight or obese. But that compared with 70 percent of men who sat for 6 or more hours each workday.

When Mummery’s team accounted for other factors, such as age and leisure-time activity, men with the most sedentary jobs were nearly twice as likely to be overweight as those with the most active jobs.

Among women, however, those who spent most of their day at a desk were no more likely to be overweight than those whose work kept them on their feet. Overall, women were less likely than men to carry excess pounds.

Mummery said he could only speculate on the reasons for the gender difference. One possibility, he noted, is that, compared with men, women get more “incidental” activity throughout the day - housework, for instance - that they wouldn’t necessarily report when asked about their exercise levels.

The findings also suggest, according to the researchers, that the level of exercise experts typically recommend - 30 minutes of moderate activity on most days of the week - is not enough for people who spend most of their work life at a desk.

Men who got that much exercise outside of work were still at increased risk of being overweight if their jobs keep them sedentary.

Large companies with desk-bound employees could do more to promote physical activity at work, according to Mummery. A “simple” measure, he noted, would be to encourage workers in elevator buildings to use the stairs instead - perhaps by making stairways more accessible, well-lit and “inviting.”

SOURCE: American Journal of Preventive Medicine, August 2005.