Battling the holiday bulge — with bacteria?

Those clothes of yours feeling a little tighter these days as you just can't resist the urge to nibble on those holiday goodies that someone always seems to leave lying around? Maybe you're already looking around for the best deals on fitness club memberships — so you can start working off those extra pounds at the gym on Jan. 2.

If you want to avoid the weight gain, you should've started working on burning off those extra calories already. A couple of preventative walks could've earned you a few guilt-free shortbread cookies.

It takes substantially more to work off your basic Christmas dinner — even a modest feast can add up to 4,000 calories or more pretty quickly. The average 155-pound person would have to walk 55 kilometres to work that off.

But don't despair. Seems all this talk about packing on the pounds over the holidays is a little overblown. Most people don't put on nearly as much weight as they think they do — maybe a pound or so.

Take that extra 2006 holiday pound and introduce it to another one in 2007 and yet another for each of the next 20 years and we're getting into some substantial regional expansion — for most people.

But do you ever notice that no matter how much some people eat, they just don't seem to put on much weight, yet others who eat moderately get bigger and bigger?

There's new research that suggests it may not be what you eat that makes you fat, but what eats what you eat.

According to two studies in the journal Nature obese mice — and people — had more of one type of bacteria and less of another kind. They both had a lower percentage of a family of bacteria called Bacteroidetes and more of a type of bacteria called Firmicutes. But the researchers aren't quite sure if the Firmicutes make people fat or if people who are obese grow more of that type of bacteria.

The researchers found that when lean mice with clean guts were given lots of Firmicutes, they got twice as fat and took in more calories from the same amount of food than mice with the more normal bacteria ratio.

So perhaps some time in the future, when the holiday binge is over for yet another year, gym memberships won't top the list of people wanting to lose weight. Maybe it'll be a heapin' helping of bacteria.