You'd have thought, when BBC Two sent me back in time to live and eat for a week in six previous epochs and discover how it felt and what it did to me, that I would have returned each time to the 21st century desperate to resume my normal diet, slavering for modern delicacies and dreaming of familiar comforts. But it didn't turn out that way.

You'd have thought that a diet drawn from the days of our nutritional innocence would make me feel terrible. Diets high in fat but low in fibre (such as the Regency); high in alcohol but low in water (such as Shakespearean and Restoration); or high in bread but low in everything else (Second World War), would surely constipate me, irritate me, give me headaches, make me terribly ill...but it wasn't like that at all.

Six times over 12 weeks, with a week off between each to recover, I was dressed up in the costume of the period, sent first to the doctor for a check-up and then packed off with my fellow guinea-pig, the comedian Sue Perkins, to a period house, built, decorated and gastronomically set up in the era to which we were “travelling”. There was often some shock at the sudden immersion, but by the end of each week the doctors were getting some astonishing results.

Every single period I ate in made me healthier. Sure, these were always the diets of the relatively wealthy, and, yes, I would probably have been stricken down young with some sort of terrible disease long ago. But as long as I did live, and had money to feed myself, I think I would have been healthier and fitter at any time in the past than I am now. We all would. And we'd all be happier, too.

We can't all escape backwards in time, as I did. We have to escape forwards, into a different future.

I do hope we still can.

The Age of Shakespeare

The earliest period into which we lunged, and the most immediately shocking. For a start, I was dressed in big, puffy knee-length trunk hose and tights with a giant codpiece, all attached to my doublet so that I couldn't wee without getting totally naked: less of a problem than you might think, since I wasn't drinking a single cup of tea or coffee, neither having yet arrived in England.

At first, it was terrible. Up at dawn to go hunting and not so much as a sniff of espresso. Irritability during the day quite terrible, not to mention the headaches. To offset these, a lot of ale and sack (sherry) is drunk, which gradually makes me much less irritable, and not in the least bit bothered about being sleepy all the time. By day five, I'm not even missing the coffee.

Dr Tom Van Den Bossche, a GP specialising in nutrition, has looked at the diet and predicted constipation and weight gain, but dishes such as calf's foot jelly are too grey and sad to eat. Likewise, a dish containing 16 live frogs falls to bits when its contents go AWOL and an hour of frog-hunting burns off all the roast piglet and swan.

As for the rest of the diet, well, who's actually going to finish a supper of sheep's head mulled in cloves? Or even start it. Straight to bed with no eyeballs: minus 1,000 calories.

Then there is treacle tart filled with pickled mackerel and herring, so barf-inducing that once again Sue and I end up ingesting precious little of this newly fashionable “sugar” we have heard so much about.

There's pumpkin pie, meat pottage, stewed mutton, boiled pigeon, calf's lungs, meat custard, numble pie (made with deer's testicles)...all sorts of delicious stuff. But in 1590, the fork has yet to be invented, and we find that eating with your hands, and feeling your digits grow stickier and smellier by the second, seriously reduces the amount you feel like shovelling in. Hey nonny, nonny.

At the end of a week in which we've consumed three times the recommended intake of protein, not to mention zero fibre and our own weight in ale and wine, Dr Van Den Bossche finds that I've lost three kilos and kicked my caffeine habit.

I have never felt better in my life. Might even write a play. Or maybe just a sonnet.

The Restoration

High protein again, and no water AT ALL to reflect people's habits at this time of dangerous contamination of the Thames. Dirk Budka, an expert in nutrition and bacteriology at the Wellman Clinic, anticipates constipation (again - no wonder they didn't invent the flushing toilet for another 200 years: chaps in the olden days clearly never pooed) and perhaps, with the dehydration and all the offal and booze, the beginnings of a kidney or bladder stone of the kind that nearly killed Samuel Pepys.

And so we sit down to such delights as neat's tongue in a caul (the tongue of an ox in the amniotic sack of a calf) and a 10kg “coffin pie” with pastry an inch thick and a reusable lid, full of coxcombs, sweetbreads, sheep's tongue, bone marrow, chicken, veal, pigeon breasts, oysters and nutmeg, which will last us a week - although by the end it is starting to go a bit green.

At first, it is awful not drinking water. Headaches and a general sluggishness ensue. But small beer (weak ale, basically) is a decent substitute, and eight pints a day of the stuff keep me in excellent spirits. After four or five days the headaches and sluggishness subside and I realise that they were just psychosomatic. The received wisdom that we should all drink two litres of water a day is just modern urban vanity, and complete rubbish: a big Puritan con designed to stop anyone having any fun that seems to have lasted 350 years.

By the end of the week, once again, I am feeling terrific. Is it the absence of fast food, and candied fruit instead of chocolate? Can it be that the 24-hour head sauna I am getting from my 5lb full-bottomed Samuel Pepys wig is keeping my brain light? Sure, my pee is like treacle and I have the breath of a necrophiliac on hunger strike, but my weight is down four or five pounds and my belly, empty of water, is hard as a rock. I am likely, apparently, to live to at least 80 - unless I get syphilis.

The Regency

Ah, the era of Jane Austen, of balls and dresses and, ah, balls and, um, dresses. They don't really eat in the books, do they? That's why they all look so good in frock coats and riding breeches. And I make a pretty awesome Mr Darcy, too. Sue can hardly keep her hands off.

I spend much of the time wearing a corset (as Beau Brummel often did, and no doubt Mr Darcy too, the old queen) and so cannot really force down much of the food - which in this period is a combination of patriotic roast beef eaten in defiance of the perfidious French and, conversely, poncy, heavily sauced French food, of the kind cooked for aristocrats by top chefs fleeing France as their noble patrons were beheaded.

I visit a Dr Petty in Harley Street, who predicts great digestive discomfort and an attack of gout from the purine in all the port I'll be drinking: during the Napoleonic wars claret was not available, so we got stinko on the sticky stuff instead, imported from our old allies, Portugal.

But I have the time of my life. Determined to keep looking rakishly handsome in my fine clothes, I burn up thousands of calories stalking my estate with a blunderbuss, firing at poachers robbing my rabbits in defiance of the Enclosures Act.

Breakfast having just been invented, I make that my main meal. But it is so recently invented that it comprises only bread, so I don't eat much of it.

Pineapples are newly available too but, you know, who gives?

As for lunch, that doesn't seem to have been invented either. But they do have a thing called “nuncheon”, which is most often cheese served deliberately with the maggots who live in it. I dine only on the occasional sandwich at the casino tables

(invented by the Earl of Sandwich for that very purpose) and so go to bed reasonably hungry - a good way to stay slim.

At the end of this immersion I do, in fact, have dangerously high uric acid, indicating the imminence of an outbreak of gout. But I am in terrific shape on the surface.

The Victorian period

As a wealthy industrialist living in a big house in Barnes and wearing a stovepipe hat at all times, I live on brown Windsor soup, cold meat pie and mutton chops. The fear is obesity, heart attack and general moral calamity.

Darwin is big in this period, not just because he was a great student of animals, but because he was a big eater of them. He ate hawk, bittern and owl, puma (“tastes like veal”) and Giant Tortoise. Sue and I do our best, avoiding endangered species and chomping down squirrel, maggot, fox, donkey, Pomeranian and even lettuce (bleurghh!).

Then there were the first curries, the first fish and chips, the first restaurant boom, fast food stalls for The Great Exhibition and a megaton Christmas involving ten courses, several whole animals, mince pies full of actual mince, and a layered pie of 24 carcasses.

But by the end of the week I have, astonishingly, lost weight. This is probably down to a sort of Atkins' effect from the meat-only diet. Furthermore, the total absence of additives or preservatives compared with a modern diet suggests that I could live for ever. This natural stuff, though leaden, is just so much easier to digest. Also I cycle everywhere on my penny-farthing, so I am fitter than ever.

Interestingly, all the protein has made me randy as hell, which is tedious, because in the Victorian era sex was, of course, illegal.

The Second World War

Who do you think you are kidding, Mr Hitler, if you think I'm eating that? Everything in the 1940s seems to have been the colour of a manila envelope: the food, the clothes, the women's legs (Sue's are stained with Bovril to look like she's wearing stockings - and are about the meatiest thing I lick all week).

We live on “national loaf”, which is bread made from whatever you make bread from when there is no wheat - I'm guessing pea flour, brick dust and hair. We also eat a lot of “national sausage”. Known at the time as Hitler's secret weapon, it was made from 3 per cent pig bits (sphincter, eyelid, sinus) and 97 per cent national loaf (see above, brick dust etc.). So you can just imagine how exciting a sausage sandwich is. Like eating loft insulation that might or might not have been slept on by a pig.

Then there's ersatz coffee, powdered egg, mock duck, mock ham, mock chicken, mock chocolate and Spam, which, alas, was not mock. Spam is truly a horror. If you fattened a weasel on axle-grease, skinned it and then pressed it into a cube, you'd get something like it, but a little bit nicer.

Otherwise it's just veg, veg, veg. Sue and I get an allotment and “dig for victory”, and with all that digging, and Home Guard drilling, and bayoneting ersatz Hun, the 100 per cent stodge diet converts into pure muscle.

We get heavier, yes, but when tested with callipers our fat mass is found to have gone down, and when put through our paces on a treadmill in a hypoxic chamber we seem to have developed the stamina of supermen. It was clearly the stodge wot won it.

The Seventies

Mark Hix, the chef who made the Ivy great, is our cook for the week, and lays before us on the first morning the food we will be eating at home. There isn't a fresh or a green thing in sight. Everything is in plastic or tin: boil-in-the-bag cod mornay, Findus crispy pancakes, frozen faggots, Angel Delight.

With all this processed food my gastroenterologist at UCH predicts totally ungroovy traffic jam in colon. And what would happen to my weight? In the 1970s we ate, on average, 750 calories a day more than we do now, and yet obesity rates were a fifth of what they are today. I usually hover around 12st most of the time, and at 5'9” that means my BMI is at the top end of healthy. A few extra pounds and I tip into overweight - which leads to self-hatred, and running. And we don't want that.

But down I chow, nonetheless. At home it is the unfeasible gunk described above, plus Mark's fantastic flambéed steak Diane with crinkle-cut chips. And then there's duck à l'orange, cheese fondue, chocolate fondue, coronation chicken, school dinners of liver and Smash followed by grey chocolate pudding with custard (skin on, of course). There's a “swingers dinner” of Fanny Craddock recipes where everything is shaped like penises and vulvae...

And at the end of the week - guess what? I'm skinny as a pencil, and now look absolutely bang on period in my skin-tight tank-tops and flares. Far from slowing down, my digestion has gone into overdrive. My body, used to the lush life of the restaurant critic, just isn't used to all this artificial and pre-fabricated stuff and simply doesn't recognise it as food. It's just passed right on through without being absorbed. Maybe that's what happened in the 1970s.

Giles Coren stars with Sue Perkins in The Supersizers Go, starting on BBC Two at 9pm on Tuesday, May 20, and running for six weeks.

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