It's hard to avoid the newest trend in town: fat is in, carbs are out. But is a high fat/low carb diet right for you? We explore why it might not be all it's cracked up to be.

why a high fat diet might not be right for you

Saturated Vs Unsaturated Fat

It's the most trendy thing in the world right now: the humble avocado. Why? Because it's high in 'healthy' fats (and because it makes for a cute emoji). Fat is enjoying a resurgence of late because, well, we need it to survive and the fact it has been demonised in the past is now being put into question. We need fat for a variety of natural bodily functions such as creating energy, absorbing vitamins and minerals, maintaining body temperature, and insulating the body's vital organs.

There are three types of fat: saturated, unsaturated (which is then sub-categorised into monounsaturated and polyunsaturated) and trans fat. Trans fat, otherwise known as hydrogenated fat, is completely synthetic and is never good for you; you could live your whole life without consuming it and you'd actually be better off for it. Saturated fat goes in cycles of scientists deciding it's bad for you, then declaring it's actually not bad for you, then changing their minds again ad infinitum. The difference between saturated and unsaturated fats is found at a molecular level and refers to the way the hydrogen molecules are bonded together. Saturated fats tend to be solid at room temperature, things like butter and cheese. Unsaturated fats are more likely to be oils like olive oil and vegetable oil however it's also found in foods like fish and nuts. 

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Which type of fat is better for you?

What's interesting is that a lot of research surrounding which types is better for you is observational or anecdotal. For example, one study found that a group of people with heart disease had higher levels of saturated fat in their diets so it was decided saturated fat must equal heart disease. However, we all know that correlation does not equal causation and a study like this doesn't actually prove that the fact these people had consumed a lot of saturated fat is what caused their heart disease.

Similarly, when it comes to how healthy unsaturated fat is claimed to be, people often refer to the 'Mediterranean diet' and how the people of countries like Greece and Italy consume larger quantities of olive oils and fish so that must be why they're all so slim, tan, and healthy. However, when you visit these countries, you realise that these people are all so fit and healthy because they walk or cycle everywhere, live up steep hills so do a lot of strenuous exercise just to buy their morning newspaper, and are more likely to work a physical job than wilt in an office all day.

Coconut oil is a saturated fat yet it is enjoying real popularity at the moment due to its supposed health benefits. So, the jury's out on which fat we should consume and probably always will be depending on whose agenda is paying the most for advertising at the time. But what we are being told is that a high fat diet is awesome for you. But is it really?

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The Keto Diet

The biggest fad diet of recent years is the keto diet. The Atkins diet reborn, this eating habit was first developed to help reduce seizures in epileptic children but people soon discovered it had more benefits than that. The keto diet is a very extreme diet and many followers will eat up to 70% fats in a day leaving only 20% for protein and 10% for carbs. Anyone you talk to who is a proponent for this diet will passionately and sometimes heatedly tell you about how much weight they lost by following it. So it must be great and the answer to your prayers, right?

Perhaps not. What a lot of keto-fans omit is that they also practise intermittent fasting as part of their keto diet. Intermittent fasting is a lifestyle that has been around for millennia and is a proven, healthy way of losing weight.  So is it the high fat diet making these people lose weight or the fact they are objectively in a calorie deficit due to the fasting? I'd argue it's the latter.

The keto diet has a whole host of nasty side effects such as 'keto flu' and halitosis (bad breath). Why anyone would voluntarily go through this process is beyond me, but it's trendy and all your favourite Instagram influencers are doing it so it must work (that's a lot of people's thinking). 

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Why a high fat diet might not be right for you

This is the real reason you're here: to find out why a high fat diet might not be the saviour we all thought it would be. Put in simple terms, fat contains a lot more calories per gram than protein and carbohydrates; over double the amount in fact. 

Fat contains 9 calories per gram. So 100 grams of pure fat would contain 900 calories (lovely thought, not.)

Carbohydrates and protein, however, contain only 4 calories per gram. So even though bread has been demonised by the anti-sugar, ant-gluten fanatics, it is objectively lower calorie than avocado gram for gram. 

What this means is that on a high fat diet you cannot consume the same volume of food that you can on a lower fat diet. The volume of food you eat is just as important as how many calories you consume because it can affect you mentally. If you're only allowed to eat 1 avocado and a ton of butter in a day rather than a truck load of vegetables, rice cakes, popcorn and other low-calorie high density foods, you're going to feel hard done by and importantly: hungry.

If you're someone who is prone to extreme hunger, binge attacks, or just doesn't have the steely, inhuman self control of pristine Instagram models, a high fat diet might not be right for you. High fat foods are easy to over-consume and you can't eat as much of them. Snacks like nuts are a big one for many people: they're told they're healthy, so they eat fistfuls every day and then wonder why they're gaining weight. A similar phenomenon started happening with peanut butter when that was enjoying its heyday on social media.

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Bottom line

We need all three dietary macronutrients to maintain a healthy diet: fat, carbs, protein. They all play their own part and have their own benefits. If eaten in moderation, anything can be healthy. Taking things to the extreme is never a good idea and cutting out whole food groups is not sustainable. Depending on your fitness training and goals, you might need more of one macronutrient than the other, but it should never be as extreme as 60 or 70% of just one macronutrient. 

Traditional 'junk food' such as cookies, cakes, and doughnuts contain trans fats which is one reason why they're so unhealthy, plus the obvious fact that they contain no vitamins or minerals and are often very high in sugar and calories. It's not because they're 'carbs'. Vegetables are carbs after all!

High-fat foods are calorie-dense meaning you can't eat as much volume. Unprocessed carbohydrates like fruit, vegetables, popcorn, brown rice, and beans can be just as healthy for you and you can eat more volume of them because they are lower in calorie pound for pound. Ultimately, balance is always key!