Comedy: Our annual chance to play the weighting game

Weight of the Nation BBC1 Horizon BBC2 Fat Free BBC1

Sometimes the BBC's scheduling is right on the button. On Thursday, Channel 4 broadcast Cold Turkey, a documentary about office parties, just when we're trying to brush all memory of them under the incriminatingly stained carpet. The Beeb, on the other hand, has got into the post-Christmas spirit by launching its "Fighting Fat, Fighting Fit" campaign. And assuming I'm not the only person who gained half a stone over the past three weeks, it couldn't be more welcome.

The vanguard of the campaign was Weight of the Nation, a programme so unusual that I'm still not certain that it wasn't a hallucination. Think of it: an altruistic, hour-long guide to healthier living on prime-time television. It had to be a hoax. These days, the BBC prefers not to be blatant about its public-service remit. Auntie doesn't want to be seen as a nanny, so she sugars her Reithian pills with soap-opera story-lines - EastEnders is promoting the Green Cross Code even now. Weight of the Nation, then, seemed to have sneaked in from a different decade, or at least a different time slot, one in which each meaningless statistic is greeted with a "wooh" from the studio audience, and each guest is greeted by a blast of music and applause; in which the host can follow an item about five men from a Birmingham social club with the exclamation, "Love those guys!" and sound as if he means it, and our ideal daily diet is illustrated with a parlour game between Barbara Windsor and Handy Andy from Changing Rooms. Andy, incidentally, is a phenomenon, simply because he's the last of a species: a "real" person on TV who isn't a natural TV star. Not once has anyone thought that Andy deserved his own chat show. He is, and always will be, a bloke who does carpentry and who doesn't give a toss about smiling at the camera or answering questions with jolly anecdotes. If his Christian name didn't rhyme with handy, he'd never have got the job.

But no, despite appearances, Weight of the Nation wasn't a parody. There was no postmodernism or pastiche beyond the coy campery of Dale Winton, and even that belonged to an earlier, gentler, less cynical era, before the introduction of the AD (Angus Deayton) calendar. Once you'd got over the culture shock, and you'd made allowances for the disastrous Handy Andy-Barbara Windsor game, it was all rather refreshing.

The campaign's message was refreshing, too. There was no talk of calorie counting or beetroot diets. There was no talk of any diets at all, for that matter, except to say that they were a waste of time. Rather than instructing us to measure ourselves against media role models or our own ideal weights, Winton and chums suggested that we'd all be healthier and happier in the long term if we ate fewer cakes and took more brisk walks. The programme was easy to swallow, and stuffed with practical advice and information. Any licence-fee dodgers who watched must have been racked with guilt.

For the science part, as Jennifer Aniston would say, Horizon opened the first of its Fat Files: "Born to be Fat". This was rather overweight itself, padded out with distracting presentation and a portentous script. (I suspect that Chris "Brasseye" Morris had a hand in the line: "He could literally eat himself to death.") There was also the inevitable trip to the US, home of the heavy, and the destination of every film-maker requiring some wacky shots of manatee-like synchronised swimmers or activists chanting, "We're here, we're spheres, we're fat, that's that!"

When "Born to be Fat" got to the meat of its subject, there was some interesting stuff to chew on. To summarise: it's a myth that fat people have slower metabolisms than thin people do. What actually controls the ups and downs of our bathroom scales is a hormone called leptin, which carries messages from our fat cells to our hypothalamus. A rough translation of these messages is: "Stop eating, I'm full up." If you don't produce leptin, or your leptin gets lost en route, or your brain's leptin receptor is on the blink, you'll stay hungry however much you eat, like the girl on Horizon whose knee-joints collapsed under her weight.

To summarise the summary: there was once a TV comedy sketch in which Elaine C Smith claimed: "I am fat, but I cannae help it. It's ma glands. I've got this gland that makes me a greedy bastard." Turns out she was more or less right.

Two days after Weight of the Nation came the first episode of Fat Free, a documentary series about five people on five different diets. As scheduling goes, this combination was like serving chips with custard. Of the slimmers we met on Thursday, one woman was on a strict diet-tablets-and-Black-Forest- gateaux regime. Another woman had progressed from "morbidly obese" to "clinically obese" via Total Food Replacement, which meant that she consumed nothing but three jugs of nutritional goop a day for seven months. A man was on a bamboozling diet involving a set number of "sins" per week and a choice of "red days" and "green days" (the dietician had to check that her clients weren't colour-blind). And in the next episode, we see a man who plans to lose 18 stone by having his stomach stapled. I don't know what that entails exactly, but I'm sure the words "stomach" and "staple" were never supposed to be in the same sentence.

What are we to make of these telly tubbies? At another time of year, our instinct would be to cheer them on, but having tucked into the uncommon common-sense of Weight of the Nation, we already know that they're doomed to tragic failure. "Diets don't work" was Dale Winton's first fat-fighting principle. Is Fat Free a series of cautionary tales, then, or are its participants just figures of sadistic fun? Either way, we're left with an unpleasantly voyeuristic taste in the mouth. Sometimes the BBC's scheduling is way off the mark.