Please walk vigorously on the spot while reading this, because apparently 10,000 steps a day might not be enough after all (it always felt like a conveniently round figure anyway). A study by the University of Alberta has concluded that a six-month exercise programme of so-called moderate intensity is a better way of achieving what one researcher called "marked health benefits" than placing one foot in front of another ad, it seems, nauseam.

But instead of taking the long route around the office to throw your pedometer into the bin - stopping to touch your toes while breathing regularly throughout - do not despair. According to Ellen Mason, a cardiac nurse for the British Heart Foundation, the "10,000-steps idea is a good way to encourage people to start; but a big failing is that many people just don't walk fast enough or hard enough".

So what is the easiest way to keep obesity at bay? (According to the current way of thinking, at least.) "Our publicity recommends 30 minutes, five times a week, of moderate-intensity exercise - like brisk walking, swimming or cycling - and one hour every day for children. You should feel warm after it, maybe a bit sweaty, and still be able to speak, but not very easily."

The parameters, then, are clear: if, after your swift perambulation/ paddle/pedal you find yourself cool, dry and sufficiently loquacious to visit the in-laws for dinner without taking a shower, the chances are you have missed the mark. If, however, you bring to mind the Scottish golfer Colin Montgomerie at the end of his singles match in Sunday's Ryder Cup, you are doing just fine.

Over in America, there seems little danger of that. The website of the US Department of Health & Human Services contains a handy list of 119 "small steps" towards larger lungs, of which, "Walk briskly in the mall" is reassuringly typical. However, since other snippets of advice include "Sit up straight at work", "Make up a batch of brownies with apple sauce instead of oil" and "Try your burger with just lettuce, tomato and onions", it seems fair to ask whether 30 minutes, five times a week will ever catch on.