Learn how to be a thin person

Here's a test to find out if you are at heart a fat person or a thin person. Do you know the meaning of 'full'? Do you know the meaning of 'too much'? If you're staying at the Pritikin Longevity Centre, the answer to these questions is probably 'No'.

One of the educational goals of the programme is to inculcate the distinction in its overweight clients between being 'not hungry' (satiety) and being full. The issue is psychological and existential; Pritikin treats it strictly as a strategic nutritional problem. "Hungry people are simply not good at eating less," Jay Kenny, one of the resident nutritionists and something of a sardonic swami, said in his lecture on 'Calorie Density and the Biology of Weight Control' which is the cornerstone of the Pritikin approach of not starving or stuffing yourself.

"Cravings are learned food circumstances. Nobody needs chocolate. They want it, but they don't need it." At one point, when Kenny got onto the vexing issue of calorie-dense olive oil ("If you're putting three teaspoons on your salad, you might as well put on a scoop of ice cream"), a stroppy Liverpudlian woman chimed in: "There's such a thing as pleasure to life!" Kenny, who is bean pole thin, shrugged his bony shoulders. "I feel like I'm talking to a bunch of crack-heads," he smiled.

The Pritikin weight control system comes down to this: calories in, calories out. Without doing anything, in each day's business of existing, the body naturally burns a certain amount of calories. This is called Resting Metabolic Rate - a crucial number which, for a small charge, Pritikin will measure for each guest. (Mens' rates tend to be higher than women's; mine was 1,640 calories per day). If you add exercising calories to the RMR - say 560 for an hour on the treadmill - you have 2,200 calories or less to eat that day; if you don't exercise, you have to keep your caloric intake below the RMR in order not to gain weight.

One of the crucial problems in dieting is that many of the calorie-dense foods which we eat (peanuts, potato chips, bread, biscuits and most fatty, greasy and oily things) don't provide enough satiety per calorie; so, to feel full you have to eat more. (An extra 100 calories a day is 10lb a year.) Eight ounces of peanuts, for instance, is 1,400 calories; a pound of strawberries is 300 calories. Many potentially healthy options become calorie-dense by what we put on them. For instance, a potato, which is only 80-90 calories and has great satiety value, doubles in calories if you add just two teaspoons of butter and skyrockets to 600 with sour cream on it.

Pritikin's strategy is to fill up on lowest calorie density food first; to dilute calorie-dense foods with calorifically light ones; and to favour water-rich foods ('eat your water') which are filling but not fattening. For instance, fresh fruit, which is rich in water, is 300 calories a pound; dried fruit is 1,300 calories.

Pritikin is against the dieting mentality; instead of skipping meals or going hungry, it tries to establish healthy eating habits. To this end, Pritikin counsels the following: avoid processed foods, don't drink your calories (27 per cent of an average American diet of 2,000 calories is taken in drink; fruit juices and alcohol are calorie-dense), eat four servings of fruit and five servings of vegetables each day, limit poultry and wild game to one hand-sized serving a week; limit red meat to once a month. "After we stop growing we have a limited need for protein," said Kenny.

By eating fewer calorie-dense foods, the body fills up and, at the same time, takes in fewer and better calories. The Pritikin solution is to lose weight and be well-nourished at the same time. "If you're not putting the right fuel into your body, it's not going to run well," Jay Kenney said. "Diet is the single most significant determinant to how long you're going to live."

TOMORROW: LYING FOOD LABELS ·