As usual for the holiday season, newspaper health pages have been full of tips on how to make it through December without looking like a fat Santa Claus by New Year’s. Watch the dip. Break out the veggie trays. “Just say no” to seconds on stuffing.

But buried among all the “easy on the eggnog” stories this month was a much more helpful clue on how to get (or stay) slim, from the U.S. Centers for Disease Control and Prevention (CDC). According to the government’s survey of almost 400,000 American adults, only about half of us are meeting the minimum recommendations for exercise.

Time after time, experts from the CDC, the American Dietetic Association, and other organizations have said that exercise is the most important factor in weight control—not candied walnuts, gingerbread, or honey-baked ham.

In July, for instance, the Journal of the American Medical Association published a study revealing that American teenagers move a mere 35 minutes per weekend day on average. And by some estimates, up to three-quarters of all trips less than a mile in the U.S. are taken by car.

As obvious as this may seem, however, this couch-potato nation appears to be in denial about for the source of our “obesity epidemic.” Rather than own up to the fact that Americans need to start moving more, nutrition activists have distracted us with campaigns targeting the “bad” food of the hour—cooking oil, artificial sweetener, salt, fried foods, soda. You name it, they’ve taxed it.

They’ve labeled it, they’ve complained about its ads, they’ve yanked it out of schools, and sometimes they’ve banned it outright.

But none of these heavy-handed fixes seems to be working. A recent study from the University of Southern Maine showed that banishing soft drinks from schools has no impact on what kids actually drink.

An expert panel reported earlier this month in the American Journal of Clinical Nutrition that there is no special link between obesity and high-fructose corn syrup, allegedly “the crack of sweeteners.”

Nor has banning trans-fat (that’s margarine, by the way) or re-zoning fast food restaurants (as Los Angeles did this year), led to any measurable decrease in obesity levels.

Is all of this really that surprising?

Even if you missed the latest news from the CDC, statistics indicate that the nutritional content of our diets (“calories in”) is virtually the same as it was in the 1950s and ’60s. Our lifestyles, on the other hand, have changed dramatically. We’re neglecting the “calories out” part of the equation.

Just think about it. Remote controls, cars, online shopping—with all of the time we spend sitting down these days, it’s no wonder that fewer and fewer adults are getting enough exercise. And that half-hour of movement on the weekends just isn’t cutting it for children and teenagers.

Why, then, aren’t more school districts re-examining their physical education programs instead of banning sodas and serving kids overpriced organic lunches?

Those extra pounds that make us panic in late December weren’t really caused by a surplus of dip or desserts. And the longer we spend trying to link obesity to things like sleep, pollution, a virus, or chemicals in paint—to name just a few recent “discoveries”—the more we’re ignoring the real problem – lack of exercise.

Unfortunately, if the most recent health-activist talking points are any indication, we can expect that this fascination with “bad” foods will continue to shape our public health policies in 2009.

Last week’s proposal by New York Governor David Paterson to tax non-diet soda and even some fruit drinks as luxury items is just a taste of things to come. Other well-known food police, like the Center for Science in the Public Interest, are now stirring up fear about “hidden” salt in our diets.

This fad-driven approach to public health is just as misguided as trying to lose weight by popping diet pills, or by filling your living room with infomercial exercise contraptions.

So forget your nosy neighbor’s tips on how to serve veggies instead of cream cheese rolls. Don’t lose sleep over that second piece of pie. Instead, we should all start looking for advice about how to actually keep that New Year’s resolution to hit the gym.

There’s no good reason to stop enjoying your holiday feast. But if we’re truly concerned about being too heavy, it’s time to get moving.