There's no mystery in staying lean

Good news/bad news on the getting older and gaining weight front. The bad news is — it's inevitable. The older you get, the more likely you are to put on weight.

We're not just talking older as in sizing up rocking chairs for the front porch. Older as in progressing from those teen years — when you can spend the day with your face planted in the fridge and the night carousing with your buddies and still look like a rake — to your 20s, 30s and beyond when hips and waists turn into fat magnets.

The good news is there's a way to slow down the weight gain. Maybe even nip it in the bud. It's called exercise — and the more you do, the better your chances of being a spectator in the regional expansion of your generation.

A study out of the U.S. Lawrence Berkeley National Laboratory found that people who maintain a vigorously active lifestyle as they age, gain less weight than people who exercise at more moderate levels.

The study followed a large group of runners who maintained the same exercise routine as they grew older. It found that those who ran more than 50 kilometres a week gained half as much weight as those who ran less than 25 km a week. A side benefit was less expansion around the waist for both men and women, and less around the hips for women.

The researchers said that while exercise alone may not keep you as lean as your teen years, it will help stave off the extreme weight gain that's associated with high blood pressure, high cholesterol, and diabetes. Committing to vigorous exercise when you are young and lean, the researchers say, would go a long towards dealing with the obesity epidemic.

The researchers focused on runners. And — when it comes to exercise — I'm biased that way too. It's the most efficient way to burn calories. A person who weighs 68 kilograms will burn around 425 calories running at a five-minute-per-kilometre pace for half an hour. The only other exercise that comes close is swimming. Doing laps at your local pool at a vigorous pace for half an hour will burn about 340 calories.

You can calculate the calories your favourite activity burns here.

Prefer gardening? You'll burn 169 calories. You'd have to garden an hour-and-a-half for every half hour I was out running. You'd still be knee-deep in weed pulling long after I was showered, relaxing and adding to my need to get out there and run again.

One more thing. Before the runners get too smug, another study found that while runners who increased their weekly mileage gained less weight than those who preferred the couch, runners who quit running gained more weight than sedentary people.

Goes to show, exercise is a life-long commitment.