Food combining is the fashionable diet torture of the moment. It was first invented in the Thirties by Dr William Howard Hay - a doctor forced into retirement at 40 because his obesity triggered ill-health. His highly- lucrative theory, supported by some American naturopaths of the time, was that excess weight and digestive problems are banished firstly, if one never eats protein and carbohydrate at the same meal but instead leaves a four-hour gap and secondly, if fruit is avoided at meals and eaten separately during the day. It works, said Hay, because their separation means the body's digestive juices can concentrate on the food type without conflict.
As Stephen Twigg elaborates in his new book, "Different foods are digested best in different chemical environments within our digestive systems, sometimes even in different parts of the system. Eating everything and anything together at one meal means one of the foods, at least, will be with the wrong cocktail of chemicals. The results will be a poorly digested meal and more toxins than necessary as by-products, which in turn lead to food cravings, bloating, fatigue, poor metabolism and, inevitably, weight gain." Inevitably? Another rule is that high-fat dairy foods ("highly allergenic") shouldn't be eaten more than one day in five. Wheat products - cereals, bread etc ("highly irritant"), should preferably be eaten even less often. Lentils and other pulses, with their dodgy combination of carbohydrate and protein, are to be avoided, too. Other Twigg refinements include "for optimal digestion, try to avoid drinking with meals" (there goes another of life's pleasures) and the advice to cut out melons which, apparently, "do not mix at all".
Thin celebrities Jill Dando, Koo Stark, Helen Mirren and Liz Hurley all endorse food combining. Such star support is more valuable than the views of nutrition scientists, but nevertheless it is interesting that for once the scientific community is united in its opinion that there is no scientific basis to food combining whatsoever. The eating habits of any culture you care to examine have always combined protein and carbohydrate with no detriment. Food combining, on the other hand, means permanent deprivation. Curry without naan bread, Chinese without rice, pasta without cheese, Mexican missing tortillas or refried beans.
The reason you lose weight, if you do, say nutritionists, is because all these food-combining diets also encourage you to cut down on excess calories and fat. The diets may be perfectly healthy, but the combination in which you eat the foodstuffs has nothing to do with it. "Evidence" of the efficacy of food combining is patchy. In The Food Combining 2-Day Detox, published by Pan last year, author Kathryn Marsden explained that food combining was recorded more than 2,000 years ago (but then so was tooth decay, and that doesn't prove it's beneficial). Marsden says combining works because "it enhances the liver, kidney and bowel function and improves digestion". But when it comes to how this is achieved, Marsden, like other food combining fans, is non-specific.
Amanda Wynne, a nutrition scientist at the British Nutrition Foundation, can, however, explain specifically why food combining is nonsense. "The human body is naturally geared to digest foods in any combination. What matters is your intake throughout the day as a whole. Different food types are digested at different places and different stages in the digestive process - for example, bile is released in the small intestine to emulsify the fat and acids in the stomach convert protein into peptide, so it makes no difference what the combination is. They will still be dealt with separately." In fact it might not be such a good idea to eat lean meat without complementary starchy fibre, which is crucial for its speedy passage through the gut.
Maybe the difficulty in sticking to a food-combined diet promotes weight loss. It is, after all, not tempting to over-indulge when dinner is puritanical polenta and vegetables. "It really worked," enthuses Sally Robbins, 33, who followed the Raw Energy Food Combining Diet by Leslie Kenton. "It made me think about what I was eating and I definitely got indigestion less often. I lost a stone and a half over three months." She adds ruefully, "I didn't keep it up, it got too restrictive. I've put the weight back on - but then if you didn't they'd never need to bring out a new book, would they?"