High Vs Low FAT Diets

by Barney St Anton in Nutrition

personal trainer | leicester

For anyone ranging from a beginner to even a seasoned veteran of the fitness world diet and nutrition can seem really complicated. There’s a lot of information out there in magazines, social media and diet books. Sometimes these messages are conflicting and it can be difficult to know who to trust and listen to. Low vs High Fat Diets are a perfect example of this conundrum. Before you go ahead and make your decision make sure you read this blog to help you decide which, if either, is right for you.

Energy Balance

THE most important thing for achieving weight loss is a caloric deficit, achieved by eating less and/or moving more. Typically I would advise clients to achieve such a deficit by removing a little bit of carbohydrate and fat from their diet whilst increasing daily physical activity levels.

I’m not disputing that high or low fat diets work for weight loss, but the reasoning behind why they work is often confused. There is nothing inherently fattening about fat or carbohydrate, other than the calories they contain. By completely removing an entire food group from your diet and not adequately replacing it your caloric intake is drastically reduced. Not only that, but so is the micronutrient content associated with fat and/or carbohydrate that cannot be replaced in other foods (Omega 3 fatty acids or insoluble fibre)

Having tried both approaches in my time I have learnt a lot and will be passing on my lessons to you, both good and bad, so that you do not have to make the same mistakes that I made.

Low Fat Diet

Firstly let’s look at low fat fat diets, or “clean eating”. Such diets are typically high in protein with regularly servings of lean sources such as chicken breast or cod/tuna, vegetables and wholegrain carbohydrates such as pasta or rice. Fat is limited to the smallest amount found in lean protein cuts or completely removed. The issue with this is that fat is crucial for bodily function and performs roles that no other nutrient can, chronic low consumption can lead to serious health concerns.

Another factor not often considered is satiation. Simply put, fat tastes good and is very filling. By completely removing it from the diet you may become increasing hungry as time goes on and increase the likelihood of your cheating on your diet and compromising progress.

High Fat Diet

On the opposite end of the spectrum we have high fat diets, which limit or in some cases completely remove carbohydrates from the diet. Such a diet is typically structured around large portions of meat, green leafy vegetables and a fat source (such as nuts or avocado) at every meal. Many people have followed the Atkins diet, or a ketogenic approach and successfully lost lots of weight, because they were in a caloric deficit.

The main reason why a high fat/low carbohydrate diet works is that you are completely eliminating a whole food group from your diet. Whilst carbohydrates do not contain as many calories as fat (4kcal/gram vs 9kcal/gram) they typically make up well over half of your daily energy intake. There is nothing inherently fattening about carbohydrates, or sugars, that means they should avoided or even completely removed from the diet.

Some people may experience rapid weight loss following a week or so of following a high fat diet, but the weight lost is not body fat. This quick drop in bodyweight occurs as our body stores of carbohydrate get used up and are not replaced in the diet. An average 80kg man will have approximately 400g of carbohydrate stored in his muscles, each gram storing an extra 3g of water. If exercising at the start of a high fat diet it would be possible for this man to lose an extra 1.5kg of bodyweight potentially skewing his view of the diets success.

Having followed a high fat/low carbohydrate diet approach previously, I can draw upon 2 positive lessons I learnt. Firstly, a portion green leafy vegetables, such as spinach, kale or broccoli, can be added to almost any meal or eaten as a side dish without ruining a meal. Additionally high fat diets put a big emphasis on foods that might otherwise not be regularly consumed in a typical diet; this includes nuts, oily fish and avocado. Incorporating these foods in to your diet is key for promoting optimal health when consumed in the right quantity for you and your goals.


Whilst it’s true that both high fat and low fat diets both work neither approach is sustainable and could lead to health problems long term. Unless you have a diagnosed medical condition, allergy or intolerance there is never any need to completely remove food groups from your diet. Instead, take the positives from each approach and aim to regularly consume vegetables with every meal including unsaturated fat sources such has oily fish, avocado and nuts in your diet whilst aiming to consume a maximum of 2 portions of fruit a day. Keep in mind that the 2 most important factors when dieting are reducing your caloric intake and finding an approach that works best for you and your lifestyle.