Does regularly stepping on the scales help a dieter lose weight?

Sure it does, say many weight- loss experts. Weighing yourself is a clear way to monitor progress or catch (and nip in the bud) a slow, steady uptick in lardage. Not so fast, say others. The glacially slow nature of weight loss, plus those spiky daily fluctuations in body weight, might actually make dieters more apt to throw in the towel.

In time for the holidays, a new study has come down on the side of daily weigh-ins. Published in the December issue of the Annals of Behavioral Medicine, it reports that dieters who weighed themselves regularly shed more pounds over a 24-month period than people who didn't. Those who weighed themselves daily lost the most.

To the authors, the implications are clear: Dieters should be encouraged to weigh themselves — and often. "We talk to people about monitoring calories daily, about monitoring their exercise daily. ... if we're asking them to do those ... on a daily basis, then why not add this other recommendation?" says Jennifer A. Linde, lead author of that study and an assistant professor at the school of public health at the University of Minnesota.

Yet there's a chicken-egg caveat here: Sure, successful dieters may weigh themselves more; but the studies don't tell you what caused what, just that the two things correlate.

It's fun to step on the scales when you're succeeding. When the numbers are nudging upward or stubbornly refusing to change ... less so.

"They're assuming that weighing yourself frequently leads you to lose weight. I think losing weight makes you weigh yourself more frequently," says Janet Polivy, a professor of psychology and psychiatry at the University of Toronto, who is not a fan of the bathroom scales.

That confusion is why, to this day, you'll sometimes get roomfuls of experts sitting around discussing an issue you'd think 21st-century science might have put to bed by now.

A curious study from the 1960s points to the potential effect of frequent weighing. Eight overweight women in a small private college were enrolled in a weight-loss plan, part of which consisted of coming in to be weighed four times a day. By study's end, the women had lost an average of 40 pounds each.

The study was small; it lacked important controls. But it was intriguing. "People in that group lost more weight than any study since then in nearly 40 years," says Dr. Joseph A. Risser, director of clinical research for Lindora Medical Group, which runs the Lean for Life weight-loss program.

The scales couldn't possibly have registered real loss from one weigh-in to the next — but maybe, Risser muses, something else was going on, such as a reminder of the mission the dieter was on.

His own studies of more than 600 clients show that those who were weighed five times weekly lost more weight (24 pounds) than those weighed twice weekly (19 pounds).

The new study by Linde and colleagues tapped statistics from two populations. One was a group of 1,800 obese or overweight adults enrolled in a weight-loss trial. Participants were asked at the study's start and at intervals thereafter how often they weighed themselves.

After one year, monthly, weekly and daily weighers all lost weight on average, but those who weighed themselves daily lost the most — about 8 pounds. (Those who never weighed themselves gained weight.)

The other data came from 1,226 adults in a weight gain prevention trial.

At 12 months, those who weighed themselves daily had lost about 2 to 3 pounds. Those who weighed themselves less often, or not at all, actually gained weight. In both studies, significant differences also were seen at two years.