'I love fat," begins Jennifer McLagan's new cookery book. This three-letter short, squat word – fat – strikes fear into the hearts of most people across the developed world, but McLagan is unrepentant in her praise of the much maligned foodstuff. "Whether it's a slice of foie gras terrine, its layer of yellow fat melting at the edges; rich, soft marrow scooped hot from the bone; French butter from Normandy, redolent of herbs, flowers, and cream; hot bacon fat, spiked with vinegar, wilting a plate of pungent greens into submission; a slice or two of fine ham eaten just as its fat begins to turn translucent from the warmth of the room, sweet, nutty, and salty all at once; or a piece of crunchy pork crackling, delicious either hot or cold. I love fat: I love the way it feels in my mouth, and I love its many tastes."

Obsessions with size zero aside, pretty much anyone born in the UK and North America over the past 50 years has grown up with the mantra of low-fat or no-fat drilled into them until the cows come home (and have their milk pumped out of them, stripped of its goodness and decanted into plastic bottles of watery skimmed white liquid). But McLagan, a chef and food stylist based in Canada, grew up in suburban Australia in the 1960s when real fat had not yet been demonised. She remembers a fridge always stocked with butter, lard and dripping, and jaunts to the fish and chip shop for chunks of battered shark cooked in tallow.

McLagan escaped to Europe in the 1970s. "When my mother was deviating from the righteous path to margarine, I was in France where there was duck and pork fat, so I kept on eating and cooking with fat," she says. Fat: An Appreciation of a Misunderstood Ingredient, with Recipes is much more than a cookery book. McLagan explains and debunks the received wisdom about how bad fat is for us, and serves up her recipes for salted butter tart, salt pork and lentils, crackling brittle and Spanish-style lard cookies with palate cleansers of historic, literary and folkloric fat facts, such as Joseph Beuys' sculptural work with malleable fat, Somerset Maugham's predilection for a good English breakfast three times a day, and the ancient Tibetan Festival of the Butter, where 10ft statues of Buddhist gods are expertly carved out of yak butter.

One expects a good chef to know the merits of a chunk of fat, but McLagan is crazy about the stuff. So enamoured is she of caul, the lacy membrane of fat that holds a pig's intestines together, she wishes someone would make her a dress out of it.

When she started hawking her idea of a cookery book that celebrated not only the merits of cooking with fat but also the health benefits, not everyone was quite so enthusiastic. "People hated the idea," she remembers. "They thought it was disgusting, especially in New York City."

Chefs have always made their food sing with dollops of butter and lashings of cream, but McLagan's voice joins a growing group of influential foodies, nutritionists and scientists who believe the foundations of the current obesity and diabetes epidemic sweeping through the developed world lie with the promotion of starchy, sugary foods over the animal fats that have sustained us for millennia.

The idea that eating a diet high in saturated fat clogs up the arteries and leads to heart disease is based on two weak reports, whose findings have instructed the Western diet for the past 50 years and led to our dependence on carbohydrates and fear of fat. The first report, from 1950, revealed that rabbits fed on a cholesterol-rich diet end up with furry arteries. Yet rabbits are designed to eat only plant life. So it should have been no surprise they reacted strangely to a radically new diet. The second study was published in 1953 by the American researcher Ansel Keyes, who made the link between fat and heart disease. He discovered an upwards curve in incidences of heart disease in six countries, starting with Japan, where people consume very little fat, through to the United States where a rampant consumption of fat seemed to correlate with a hike in cases of coronary illness. Keyes conveniently ignored data from 16 countries that did not suit his hypothesis, including crucial research on French and Inuit people, which showed they ate large quantities of fat and rarely suffered from heart disease. A fascination with the Mediterranean diet ensued and, although Keyes' work has since been largely discredited, our enthusiasm for fruits, cereals and vegetable oils has remained.

The American National Heart, Lung and Blood Institute has found no link between diet and heart disease. In 2003, Professor Sylvan Lee Weinberg, a former president of the American College of Cardiology, said there was no longer any defence for a low-fat, high-carb diet. A 2008 report in the American Journal of Preventative Medicine actually pointed the finger at US dietary guidelines for the rise in obesity. "Ironically, it now seems that the US dietary guidelines recommending fat restriction might have worsened rather than helped the obesity epidemic," concluded the report, by Marantz, Bird and Alderman.

Not only is fat not bad for you, it has lots of properties essential to our wellbeing. "You need fat to absorb certain vitamins," explains McLagan. "It is full of stuff that boosts your immune system and is connected to your hormones."

Fat also tastes delicious, something we have forgotten with the passing of time and our dalliances with polyunsaturated margarine, sunflower oil and skinny lattes. "We have sacrificed all that taste and pleasure," says McLagan, "yet we haven't lost weight or improved our health." She is not advocating you snack on her bacon fat spice cookies throughout the day, but firmly believes that three meals that include proper fat will keep restless fingers out of the biscuit tin.

McLagan is not immune to our fear of fat. Faced with a slab of pork belly, even she hears that voice in her head wondering if it will make her fat. But she knows that starving herself and restricting her diet is the only sure-fire way to put on weight. "The main reason I wrote the book," she says, "is that fat is flavour. Everybody has to eat and you might as well eat tasty, satisfying food."

McLagan points out that we are not only frightened of eating butter, lard, suet and dripping, but also fearful of the pleasure that indulgence brings. You'll have to pass on the Ryvita and abandon yourself to McLagan's chicken liver spread and brown butter ice cream to find out if she's right.

On the menu? Know your fats

Butter: Mainly saturated fat, which should be refrigerated and well wrapped to protect it from light and absorbing strong smells. Humans have been eating butter for more than 10,000 years.

Lard: Real lard is hard to find, so terrified are we of the creamy rendered pig fat. Foods fried in lard become very crisp and absorb less fat than foods cooked in oil, and it makes great flaky dough.

Lardo: Lardo is an Italian delicacy that is enjoying a renaissance. It is cured pork back fat that has been aged for long periods in a cellar. Eat thin, seasoned slices on toast or use to flavour pasta or rice.

Dripping: This is the fat that drips from meat while it cooks. Beef dripping is the most popular. Brown beef or lamb in their own dripping and the flavour will intensify.

Suet: This fat surrounds an animal's kidneys and is rarely found any more. It is a hard fat with a high melting point so great for deep-frying and making pastry. Grate it into your mincemeat and dumpling mixes.

Tallow: A general term for fat rendered from cows or sheep, best known as an ingredient for candles and soap. Save some for your roast potatoes and Yorkshire puddings.