Diet books are terribly passe these days. Instead of calorie counting, everyone is "eating for health": food combining, the anti-candida system, allergy eradication attempts. Last week, I met a German doctor who advised me to begin a "low acid" eating programme, avoiding rhubarb, wild cherries, gooseberries, yoghurt, sauerkraut, vinegar, vitamin C, margarine and meat. A few days later, a nutrionist urged me to give up wheat, oats, rye, barley, dairy products, sugar, salt, tea, coffee, chocolate and, of course, alcohol.
The new ideology - emphasising health, not weight loss - may be different from the old, but the advice is the same: contradictory, ever-changing and impossibly austere. A few hours after I met the nutrionist, I ate four slices of walnut cake.
The other growth area is the anti-diet book, a genre pioneered by Susie Orbach in the 1970s with Fat Is A Feminist Issue. Eat Fat by Richard Klein covers much of the same ground: the historical rarity of the emaciated ideal; the greed of the medical-health-beauty industry; the damage that dieting can do to the body; and the scary new generation of "anti-obesity" drugs.
What is new about this book is, in part, its tone. Klein, a professor of French at Cornell University who once rode in a car with Roland Barthes, declares Eat Fat to be a "postmodern" diet book, lo on angry sexual politics, hi on fun. He aims to charm, not shock, the reader into giving up diets. "This book is designed to be thrown away," he writes. "Once you have consumed it, the text should vanish, and remain a delicious memory, like the faint recurrence of the feeling of well-being that accompanies the disappearance into your mouth of a chocolate truffle."
Thus Klein (who weighs 200lb) breaks off from expressing rage at the word obesity to write about his fat mom and fat sister: "They've both been dieting for decades...and have been getting fatter and fatter." He explores Fat Admiring sexual subcultures, from the endlessly frustrated Chubby Chasers ("They are looking for fat women [like glamour model Teighlor, who once weighed 719lb] with self-esteem, who love themselves fat") to the happier gay world of Flabio and Bulk Male. Later, he stops exploring the relationship between power and fat ("It's not money the rich are afraid to spend, but calories, which are worth more than money") to ask: "Why are Americans obese? Ask a Frenchman."
Klein's book isn't so much an anti-diet book but a pro-fat book, and he worships it with the sensuality of the best cookery writers. His love of fat is comprehensive, from the pleasure of plump olives to the sweet power of Jessye Norman, from 18th-century fat ("The creamy skin of those large dollops of pink women," begins his hymn of praise to a Boucher painting) to the ultra-modern. "She slips me an extra slice of toast," he writes of the waitress in his local diner, "heavily buttered. I really don't need it, but...I eat it all, because she loves me. Because with the wind howling and the snow sweeping through barely plowed streets, that fat is a kiss, between her and me."
Klein's really big idea is that diets make you fat: not physiologically, as many nutrionists now believe, but philosophically. The more we diet, the fatter we are getting. Between 1980 and 1991, the proportion of overweight Americans rose from one in four to one in three; when Hillary Clinton installed a healthy, fish-grilling chef at the White House, the president gained weight. The lower in fat they are, the more crisps we eat. Ergo, says Klein, if we stop dieting, we'll get thinner. In which case, I'll have another slice of that cake.