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In the battle against obesity, fat often gets demonised by the media. Lara Medlam investigates the science to find out the truth between the good and the bad fat

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Image: Kate Ter Haar
Image: Kate Ter Haar

Fat is fat, right? Unfortunately it isn't quite so simple. Monounsaturated, polyunsaturated, saturated, transunsaturated. What's the difference between them all, where are they found, and does it even matter anyway? I'm not going to claim I'm an expert, or even a chemistry or biology student. However, when it boils down to it, you don't need hugely in-depth knowledge to help demystify (and de-clog) all the confusion surrounding fat in the diet. Humans have evolved to need and want fat. The fat you eat is broken down into smaller units called fatty acids, and any that is not used by your body's cells or to create energy is converted into body fat: the cushioning, insulating stuff.

So where do the 'good' and 'bad' fats come into it? There's been a lot of varied reporting in the past few years, a reflection of the current health crisis gripping the UK. If only people knew the difference between their good and bad fats, the obesity crisis would be sharply averted! Well, although it's not that easy, forming a basic understanding is pretty simple. All fats contain the same amount of calories, 9kcal/g, whereas protein and carbohydrates contain 4kcal/g. Therefore, highly fatty foods are referred to as energy-dense foods because they pack the calories in. This is why whale blubber formed an important part of the Inuit diet, or why rich milk has been fed to growing children for centuries. For those living in naturally scarce environments, or if you're busy hiking up enormous mountains, there's a great need for fat and the energy it provides. However, in this modern age of plenty, our ability to store fat for lean periods seems counterintuitive.

With current worries about diet and health, and conflicting reports about different fats, it's difficult to know how to approach our instinctive need for fat with a healthy outlook. In such a context, it helps to break it down.

The good fats are the mono and polyunsaturated; the naturally occurring fats which your body actually needs. Monounsaturated fats are found in oils, namely olive, peanut, and rapeseed. Avocados are full of them, as well as nuts and seeds. It's why these foods seem slightly contradictory. You go and buy some nuts as a healthy snack, and are aghast when you look at the nutrition values. However, since they're full of the good monounsaturated fats, are unprocessed and similarly rich in minerals and vitamins, it's not an issue.

Image: Jerad M. Gardner
Image: Jerad M. Gardner

Polyunsaturated fats contain those crucial omega-6 and omega-3 fatty acids. The body is unable to produce these, making their presence in one's diet all the more important. And it's why your mum was keen to give you those manky fish oil capsules which had the worst habit of repeating. Omega-6 is found in oils such as sunflower, flaxseed and walnut. These are the various interesting oils you find in fancy delis and health food shops (i.e. you can pay a lot for them, but standard, unrefined oils will do the job). Omega-3 is the preserve of oily fish: mackerel, trout, sardines, salmon. Getting enough omega-6 isn't generally a problem, but current guidelines promote greater consumption of omega-3, by eating two portions of fish a week.

Saturated fat is a contentious one. It's found in its highest concentration in animal foods, such as milk, meat and butter as well as some plant foods, like coconut and palm oils and even lean meats, such as chicken, contain a small amount of saturated fat. For decades saturated fat was seen as evil, the root cause of our dietary woes. However, recent research has suggested that our pre-conceived notions are arguably misguided. In the 1970s, the rate of heart disease rose rapidly. Whilst some researchers at the University of London found sugar to be the decisive culprit, this view was overlooked.
There was far more financial gain to be found in demonising fat than sugar. Hence the irresistible rise of the low fat option.

However, a 2014 paper in the Annals of Internal Medicine jolted many widely held opinions about saturated fat. New evidence questioned the assumed link between consuming saturated fats and cardiovascular disease, and claimed it "does not support" current consumption and heath guidelines.

The common consensus is that trans-unsaturated fat is the one you want to avoid, it's the nasty one. Commonly found in processed foods, baked goods and snacks, it's made by heating vegetable oils in the presence of hydrogen, creating hydrogenated vegetable oil. When it was first created in the 1950s it was thought to be a healthy alternative to saturated fat, yet it's anything but. Trans fat has become a modern food industry obsession, as partial hydrogenation not only makes oils more stable and less prone to going rancid, but the oils can also withstand repeated heating without breaking down, making them ideal for frying foods. Trans fat is not only the greatest contributor to cholesterol in the body and increases the risk of diabetes but even a small amount can have harmful effects. For each additional 2 percent of calories consumed daily from trans fat, the risk of coronary heart disease is increased by 23 percent. Given that heart disease is the world's leading cause of death, this figure is both brutal but sadly unsurprising. It seems many don't realise quite how insidious the effects of trans fat are. Whilst the US Food and Drug Agency are working to eliminate partially hydrogenated vegetable oils from the food supply by 2018, the decision still only came after decades of lobbying by health advocates and scientists.

Realistically, we're not all going to stop eating chips and chocolate. However, a basic understanding of the effects of our food is a step in the right direction for national health. Recognising the necessity of fat, but being aware of its harmful forms is a good way of thinking about your diet as a whole, particularly relevant since as we've become more modern and industrialised, so too has the food we eat. However, for every down there's an up - as proven by the growing concern in and awareness of the actual effects of what we consume.

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1 Comment

Lily Posted on Saturday 11 Jul 2020

Makes everything so much clearer! Thanks.


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