POURING tomato soup through someone鈥檚 nose is sometimes the best way to discover why Christmas is a weight-watcher鈥檚 worst nightmare. OK, so it鈥檚 a far cry from turkey with all the trimmings, but this is still the cutting edge of 鈥渉edonics鈥�-the study of gastronomic pleasure. Sit back, relax, and loosen your belt another notch if it makes you feel more comfortable, because what you鈥檙e about to read may leave you feeling rather queasy.
There鈥檚 a lot we don鈥檛 understand about the problems of overeating, but Martin Yeomans of Sussex University and Steve French of Sheffield University have set themselves the task of probing the mystery. Yeomans and French are the 鈥済ood cop, bad cop鈥� of appetite interrogation-the one specialising in the pleasures of eating, the other an expert on fullness and the pain of overindulgence. Between them, they鈥檝e just about got it covered. Yeomans can explain that irresistible urge some of us have to trough an entire litre tub of Ben & Jerry鈥檚 Caramel Chew Chew even though we鈥檝e just eaten a full meal. And French knows why feeling full to bursting point prevents most people-Mr Creosote excepted-reaching for that last, explosive, wafer-thin mint. 鈥淭he novel aspect of our work is trying to bring together two parallel strands and see how they interact,鈥� says Yeomans.
Hedonism research is no box of chocolates. In fact, for Yeomans and French鈥檚 volunteers it is mostly tomatoes. For starters they get tomato soup-through the nose if the researchers want to measure the satiating effects of various nutrients independently of any eating pleasure they might provide. Soup is followed by pasta with-you鈥檝e guessed it-tomato and onion sauce. The 鈥渢asty鈥� version of this dish contains herbs and seasonings and the 鈥渂land鈥� variety comes au naturel. It鈥檚 a lonely business pushing out the frontiers of appetite research. Each volunteer is tested separately, with only a computer as a lunchtime companion, secretly assessing how much of the palatable or bland food he has eaten and interrupting him every few forkfuls to ask how he is feeling vis 脿 vis the old appetite. Christmas dinner it is not, but the results are incontrovertible: tasty food initially boosts hunger more than bland food, it makes you feel full more slowly, and leaves you eating more overall.
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But if there鈥檚 one thing this duo has learned in almost a decade of nasal drips, intragastric infusions and tasteless pasta, it鈥檚 that there鈥檚 no simple explanation for gluttony. Their distasteful experiments have convinced them that how much we eat depends on the outcome of a battle between the opposing forces of pleasure and satiation. And if some of you are already reaching for another mince pie, muttering that with all the pleasure on offer at this time of year you can鈥檛 be held responsible for your actions, then tuck in, because you鈥檙e probably right. French, Yeomans and an assortment of other appetite researchers have evidence that confirms the worst fears of every calorie counter-Christmas really is out to get you.
Everything about the festive season makes you overindulge. Just take a look at the 鈥渂ig meal鈥� itself. The simple act of sitting down with those you know and love has already sealed your fate. John de Castro from Georgia State University in Atlanta has found that in the company of friends, you can expect to put away 44 per cent more nosh. Your consumption increases in proportion to the number of people at the table and, worse still, the more you鈥檙e enjoying yourself, the more courses you鈥檒l eat.
You will probably start with an aperitif. It may look harmless, but Yeomans鈥檚 experiments show that a single tipple before you tuck in sets things off on the wrong footing. When he plied some of his gastronomic guinea pigs with a libation disguised as apple-flavoured pop shortly before lunch, they ended up eating more than other volunteers who had consumed real soft drinks, even though they had no idea they had been drinking alcohol. And 鈥渂ah! humbug!鈥� to diet coke drinkers who think they can fill up on carbon dioxide and aspartame, because several studies show that only drinks containing large amounts of real sugar will knock a hole in your appetite.
You might want a snack with that drink. Go on, treat yourself to a sliver of salami, or perhaps a nice creamy dip with some of those hand-fried potato chips on the side. Breadsticks and other carbohydrate-laden, low-fat snacks can take a back seat because, well, it鈥檚 Christmas. But be warned: you鈥檙e bound to be nobbled by those high-fat nibbles, because you are destined to eat more of them-even supposing they tasted no better than the carb-rich, low-fat alternatives. The explanation, according to French, is that despite containing fewer calories, high-carbohydrate snacks fill you up more than fatty ones. So don鈥檛 trust your body to regulate your calorie intake: go easy on the cheesy footballs.
Sooner or later, Christmas dinner proper will make it onto the table. And that鈥檚 where your problems really begin. For an hors d鈥檕euvre you are bound to be faced with a rich little morsel-smoked salmon, p芒t茅 perhaps or something with a more highfalutin French name, looking beautiful and dripping with cholesterol. You would be wise to think of this as the place where art meets arteriosclerosis. The look, the smell and that initial burst of flavour all conspire to produce the hedonic qualities that are Yeomans鈥檚 speciality. A few mouthfuls of this pleasure-on-a-plate and, his studies show, you actually become hungrier than you were before you began eating.
It鈥檚 all going horribly wrong. And it gets worse. Whereas appetite researchers had traditionally thought that we compensate for a calorific starter by eating less later in the meal, that鈥檚 simply not true, according to Yeomans, French and co. They concocted some high- and low-calorie soups, and fed them to volunteers who didn鈥檛 know which was which. The volunteers were then allowed to eat as much of a given main course as they wanted. The ones who had started with the high-calorie soup ended up consuming around 1000 kilojoules more overall than people given the meagre starter.
And it didn鈥檛 make any difference whether the starter calories came in the form of fats or carbohydrate. Some appetite researchers have reported that fatty foods cause people to eat less but Yeomans suspects this effect is psychological rather than physiological- if you know that a particular starter is destined to become an insulating lining for your arteries you may consciously rein back during the main course.
Anyway, enough of the starters. Let鈥檚 move on to the main attraction, the grand spread. The festive table is groaning with goodies, myriad assorted dishes making a full-scale assault on your senses. The needle on the 鈥渉edonometer鈥� is off the end of the scale and you鈥檙e in big trouble. Whether you are a traditionalist content with turkey and all the trimmings, a gourmand who likes to experiment with swans鈥� tongues, wombats鈥� pouches and pigs鈥� ears, or a vegetarian happy to graze on spicy nut loaf and assorted pulses, the key word here is 鈥渧ariety鈥�. That鈥檚 because variety is the source of strife. Barbara Rolls from Pennsylvania State University has shown that people given four different types of food guzzled 60 per cent more at a sitting than those fed on a single item, even if this single item was their favourite. Astonishingly, if you are given a mixture of three pasta shapes you鈥檒l down 15 per cent more calories than if there was just one shape on offer.
And when variety combines with deliciousness, the bathroom scales had better prepare themselves for a battering. Perhaps you don鈥檛 need Yeomans and French to tell you this, but you will find your Yuletide spread more tempting than an unlimited supply of gruel. Their experiments have confirmed the simple truth that the yummier the food, the more we eat. Based on their premise that appetite is a balance between pleasure and pain-between the hedonic value of the food we are eating and the uncomfortable feelings associated with being stuffed to the gunwales-it doesn鈥檛 take a rocket scientist to figure out that you are going to need a considerable amount of pain to outweigh the pleasures of this particular meal.
And that鈥檚 even before you have added liquid refreshment to the equation. There鈥檚 still debate about whether or not alcohol makes you fat (快猫短视频, 27 November 1999, p 50), but there is no getting away from two facts: first, pure alcohol has 29 kilojoules per gram (that鈥檚 only about 8 kilojoules less than pure fat) and second-and, perhaps, more dangerously-alcohol lowers your inhibitions. 鈥淭he jury is still out on what alcohol is doing at a metabolic and physiological level,鈥� says French. But whether or not it makes you feel hungrier, it is bound to summon that little inebriated voice in your head telling you to throw caution to the wind. What the hell, the diet can wait until tomorrow.
In the meantime, there鈥檚 dessert to think about. Will it be plum pudding with lashings of brandy butter, passion fruit pavlova or the cr猫me br没l茅e? All three options are high in sugar and fat, which, research indicates, take longer than protein to induce that fit-to-burst feeling. French thinks he knows why. 鈥淥nce nutrients are absorbed, the next place they have a big influence is in the liver,鈥� he says. Here they are oxidised in a reaction that somehow creates feelings of satiation. 鈥淭here seems to be a hierarchy of metabolism,鈥� says French. Proteins are broken down first, then carbohydrate and lastly fat. Which could explain why protein fills you up faster, and fat fills you up least quickly.
Better try a little of each dessert then. And while we鈥檙e at it, pass the cheese board. You can surely find space for a few hundred blue-veined calories-stilton does pack them in so efficiently, after all.
At this stage you may find yourself flagging. But the Christmas dinner has another trick up its sleeve. Coffee will shortly arrive to perk you up. We know caffeine stimulates your central nervous system and dilates blood vessels, but some research suggests it also increases gastric secretions. Result: a surge in appetite in time for the chocolates.
Bloated now, you may already be vowing never to eat again. Give it a couple of hours, though, and you鈥檒l be tucking into a mince pie or some fruit cake. If you keep this up, your stomach will gradually expand, allowing you to shovel ever greater quantities of food into it before stretch receptors in its walls scream out to the brain for mercy. But the pain is worth it: once stretched, your stomach will have extra capacity for tomorrow鈥檚 Boxing Day feast.
If you really can鈥檛 stomach the thought of a whole week of gorging yourself silly, the best way to exercise self-control is probably to lock yourself away in a cupboard with a half ration of Ready Brek. Alternatively, there鈥檚 a more scientific solution. High-fat food fed directly into the duodenum fills you up more than the same food eaten the conventional way. French and Yeomans鈥� work even suggests that a blast of fat to the stomach may also do the trick. The downside is that you鈥檒l need to be fitted with a plastic tube running through your nose, down your throat and into you digestive tract. The prospect of sitting around the dinner table at Christmas ingesting cheese souffl茅, duck 脿 l鈥檕range and tiramisu via a nasal drip is probably too gruesome for all but the most dedicated weight-watcher to contemplate. Maybe it鈥檚 best just to accept your fate. Eat, drink and be merry, for tomorrow we diet.