Wonder fat that makes you run and run

John Carlin on a new slimming aid with unpleasant side effects

THE AMERICAN Dream comes in a variety of shapes and sizes. One of them is to eat a lot and stay thin.

In pursuit of the primary Dream, which is to make lots of money, American food manufacturers label all their products either "low fat", "reduced fat" or "fat-free". Yet venture into your average mid-Western supermarket and you could be forgiven for imagining you had stumbled into a convention of sumo wrestlers.

The impression is backed up by the figures: one in three Americans - up from one in four during the Seventies - are officially defined as obese.

"Low fat", it turns out, is an invitation to eat too much; "fat-free", to eat something that is fat-laden. What America clamours for is food that is fatty but non-fattening. Procter and Gamble have spent the last 25 years trying to come up with the magic formula. It appears that their scientists have done the trick.

The Food and Drug Administration (FDA), the most rigorously vigilant institution in the US government, is expected this month to declare that Olestra is fit for public consumption. Olestra is a synthetic fat adaptable for all types of cooking. You can bake cakes with it, make ice-cream, fry fish and chips. And yet, and yet - oh triumph for guilt-free gluttony - Olestra is not absorbed by the human body, it does not translate into glutinous deposits in the bottom, thighs and belly. It goes in one end and comes straight out the other - which can cause complications, but more of that later.

Let us, for now, accentuate the positive.

This is how regular animal or vegetable fat insinuates itself into the human system. You swallow, say, a crisp, a regular crisp that's been fried in corn oil. Having made its way down the alimentary canal, through the stomach to the intestines, your crisp is mugged by a gang of enzymes. The enzymes steal the crisp's fatty acids and run off with them into your bloodstream.

Now, a crisp fried in Olestra is an altogether tougher proposition. Olestra is a man-made hybrid of half a dozen vegetable oil molecules and - here's the critical ingredient - a sugar molecule. The sugar molecule does for Olestra what spinach did for Popeye: makes it bigger, stronger, more muscular and tightly packed than natural fat.

So when the crisp - Procter and Gamble mean to christen it "Olean" - reaches the intestines, the Olestra robo-fatty just brushes the scavenger enzymes aside and strides on, undigested and invulnerable, towards the watery fate that awaits it on the other side of the colon.

The good news is that eating two bags of Olean crisps is the equivalent, in calories, of eating one bag of regular crisps. As for taste, numerous experiments with human guinea pigs have demonstrated that most people cannot distinguish between a crisp made with Olestra and one made with vegetable oil.

The bad news can be summed up in two words: anal leakage. That, at any rate, is the term used by medical scientists to describe the difficulties the sphincter might encounter in holding back the mighty Olestra. There is also a fear among a group of scientists at Harvard that Olestra might share some of the intestinal enzymes' larcenous tendencies. They say that the Olestra fat, acting like a sponge, will absorb vitamins and nutrients necessary to prevent cancer and heart disease. The sceptics accept, however, that it might take decades before their theories are proven.

Of more significance to the American consumer is the decision by FDA scientists to decree with "reasonable certainty" that Olestra does no harm. Though they have acknowledged that, in addition to anal leakage, Olestra can cause bloating and flatulence. Which is why, in a reminder that there is still no such thing as a free fat, they have recommended that food products containing Olestra should carry a warning that reads: "Foods that contain Olestra may cause intestinal discomfort or a laxative effect."