THEY do it on purpose, don’t they? As I slip another Turkish Delight Thin into my mouth with one hand (like After Eights, but rose-flavoured rather than minty) a click of the computer mouse with the other mitt brings up a health warning guaranteed to dampen Christmas over-indulgence.

The average British man was more than a stone heavier in 2000 than in 1986, reckons an Oxford University study. Personally, looking at how body mass index inflation has sent my telltale dimensions rising faster than petrol prices over the past decade – waist, chest, collar size – that’s a conservative estimate. I know it; I just don’t want to be reminded of it. And certainly not at Christmas!

Of course, that’s probably why conscience-pricking news is released at this time of year: so it preys on our guilt as we lie there, vulnerable and flabby in our post-turkey-and-pudding glow. We must do something about it, we mutter.

Lo and behold! A glorious opportunity presents itself: a new year and the chance to make a resolution that will shape a better life. I don’t make such pledges – most people do so only because of tradition, and the impetus evaporates by February – but I have already planned, independently, a new dawn for 2011. For, sadly, I’m one of those ticking time-bombs of which The British Heart Foundation speaks: a sort of human Danger UXB in need of defusing by regular exercise and a more balanced diet.

Actually, the diet bit isn’t too bad – as long as I finally banish the afternoon chocolate bars and evening crisps. The male weight gain spoken about in that university study is partly explained by us eating more calories than we need, but more culpable is a drop in exercise.

Researcher Dr Peter Scarborough says: “The problem is really how people are getting around. They are driving more, cycling less and more likely to be employed in a sedentary job. Physical activity is slowly being removed from day-to-day life.”

Guilty on all counts (if we ignore a short trot to the drinks machine). That’s going to change, though, with more exercise scheduled . . . as long as I can quell anxiety about leaving work on time. So many people I know find that difficult to achieve during this period of economic wobblyness, when you feel you have to do all you can to safeguard your position.

Still, I have some comforting food coming to fortify my resolve, thanks to a friendly family round the corner. A new study suggests Neanderthals cooked plants and vegetables, and weren’t simply meat eaters. My neighbours, taking a leaf from The Pre-Ice Age Cookbook, do a mean low-calorie wheat-and-kelp dip . . .