Review: "Fat: an appreciation of a misunderstood ingredient, with recipes" by Jennifer McLagan

I don't usually spend long in the cookery section of charity bookshops. The sorts of books languishing there tend to feature fad diets, few pictures and chefs nobody has heard of. So the cover of this one did more than catch my eye - a big juicy chop replete with hunks of creamy white fat, and a title all the more provocative for its drab surroundings. Eagerly I flicked to the back cover in search of a photograph of Ms McLagan. Surely I would discover a rotund, ruddy-faced woman, flour-dusted sleeves rolled up to the elbows and clutching a rolling pin in one porky fist? No! A petite woman with round glasses smiles smugly, "you weren't expecting that, were you?". Several minutes later, the volunteer at the till was rather bemused by my enthusiasm.

This is a book that tells you something you want to hear: animal fat is not the enemy. It won't kill you, and maybe it's even good for you. It is essential for cooking, and conveniently, it tastes spectacularly good. The introduction attempts round up the rather sticky health issue, but the tempting and rather more convincing arguments of taste, usefulness, and tradition keep muscling their way in on the science. There are two big health questions: does eating fat make you fat? And will eating animal fat give you heart disease? I think we can boil it down to two issues: all fats are not equal, and science is not as impartial as we'd like to believe.

Lipids, it turns out, are an enormous and highly varied class of chemical. All fatty acids are essentially chains of carbon atoms, each with a pair of hydrogens attched (you could think of this like cheese and pineapple on sticks studding a foil-wrapped swiss roll). If all the carbons have two hydrogens attached, the fat is solid at room temperature (the guests are unlikely to attack the swiss roll while it's groaning with all that cheese and pineapple). When one or more hydrogens are missing, the fat is unsaturated, and tends to be unstable at room temperature (once the swiss roll is discovered, it's unlikely to stay wrapped in foil).

We are all familiar with the words 'saturated', 'mono-unsaturated', 'polyunsaturated' in the context of fats. The fitting of fat into categories lends itself to comparison, and the labelling of one or the other as 'bad', or 'worse'. Most people would suggest saturated fat is unhealthy. But what happens when we digest fat, beyond the GCSE-science of it being emulsified and broken down by lipase enzymes, is complicated! Having done more than a bit of casual research, I'm not all that surprised that the discussion in McLagan's introduction is neither clear nor in-depth. There are a few simple facts that we can take away:

- Animal fats are always a mixture of saturated, monounsaturated and polyunsaturated fats. Lard, for instance, is 39% saturated, 45% monounsaturated and 11% polyunsaturated. The types of fats present are affected by what the animal ate; e.g. grass-fed beef is richer in omega-3 fat than is corn-fed beef.
- Some vitamins are only soluble in fats, so if you don't eat enough fat then you stand to lose out on vitamins A, D, E and K.
- Fat molecules are large and take longer to digest than, say, refined carbohydrates, and the effect of this is that you feel more satisfied, for longer. This could make you eat less, and snack less between meals.
- Everyone agrees that trans-fats are bad. Hydrogenating vegetable oil by bomarding it with hydrogen is a convenient way for the food industry to make stable fat, but trans-fats don't occur in nature so it makes sense that our bodies don't know how to deal with them.
- The general consensus is that it is excess sugar and carbs which cause weight gain, not fat.

The fairly recent history of fat's bad reputation shines a light on another topic - the link between science, politics and big business. It is widely accepted that a diet high in saturated fat and cholesterol will put you at higher risk of developing heart disease. But how conclusive is the science? The theory was first advanced in the 1950s, when heart disease was emerging as a major killer in the western world. The evidence that backed it up was associative, rather than causal - this is, it seemed that people who ate more fat were at greater risk, but we weren't sure about the biological reasons. Other studies found little or no evidence for a link. But in the 1970s the US government decided to endorse the theory anyway. After this point, it is more difficult to publish unbiased research. Funding from governments and business is more likely to continue if the funders get the results they want - so the scientists find themselves incentivised to present the results in a certain light. Suddenly the debate is all but over.

What isn't a matter for dispute is that fat is indispensible in the kitchen; once you are even semi-convinced of the health benefits you can fully embrace this part. Fat is the part of meat which carries flavour. I can tell you this is true because as I write I am rendering some bacon fat (of which more later), and it smells identical to bacon cooking. Many flavours and aromas are soluble only in fat: no fat, no taste. It is disappointing to read that our fear of animal fat has lead to the rearing of leaner animals. We have colluded in intensive livestock production, in which animals grow quickly and don't have time to develop tasty fat, by demanding lean meat.

The book examines different fats in turn, starting with butter. My exposure to butter thus far was normal, but for two experiences. The first, some years ago, involved a friend making butter on scout camp - the rescuing of some enthusiastically whipped cream on a hot summer's day, strained through the cleanest tea towel we could find. The process was intriguing, but I think I was more fascinated by the fact that my friend knew how to work this magic. I don't really remember eating it. The second experience was eating my mother-in-law's homemade butter - before I had met her - and despite not being wholly convinced that it tasted better, I did have my eyes opened to the fact that "real" butter might be different. Clarified butter was just something they talked about on Masterchef; ghee was a mysterious ingredient found in curry recipes. Courtesy of this book, I can reveal now that clarified butter has just had its milk solids strained out (those are the bits which burn if you let the pan get too hot) and ghee is basically the same but cooked for longer, to infuse the taste of the cooked milk solids. This means you can heat it to a higher temperature, and it doesn't go rancid so easily. Makes sense if you live in a hot, curry-loving place. I have made some according to the instructions in this book (Madhur would be proud). It was surprisingly easy.

Rummaging in the freezer looking for something for the slow cooker pot, I found some lean diced beef, and felt slightly ashamed. I have triedto make up for this transgression by baking a batch of 'bacon fat spice cookies'. When I demanded from the butcher some bacon "with a decent amount of fat" I had to confirm that I meant "a lot". As McLagan points out, "eating animal fat didn't kill our ancestors", and "it wasn't smart to dismiss thousands of years of empirical evidence". This is just as convincing to me as the political war over heart disease - enough at least to stop feeling guilty about fresh bread smothered with butter, or a big slab of pork belly. So how did this veritable bible end up in the Oxfam shop? I guess somebody just didn't have the stomach - their loss is my gain.

Fat is published by Jacqui Small (2008), RRP £16.99.