The Truth About Dietary Fat: From Zero to Hero
- Dr Neel Gupta
- Aug 22, 2023
- 5 min read
Updated: Aug 24, 2023
Our diet is made up of only 3 macronutrients: carbohydrates, fat and protein. Fat is an essential component of our diet. It forms part of the membrane around every one of our cells, is needed to absorb certain vitamins, is vital for the production of hormones and has many other important functions. Our body can produce most of the fats that we need for survival but not all of them. Some types of fat must be consumed in the diet; we call these types of fat “essential fatty acids”.
Despite its crucial role in our survival, for as long as I can remember dietary fat has been demonised. Fat provokes perhaps the single commonest source of confusion when it comes to healthy eating. If you asked the average person about dietary fat they would invariably say that a diet high in fat is unhealthy, based on two ideas that have been hardwired into us:
Eating a lot of fat makes you fat
Eating fat (in particular saturated fat) leads to heart disease
These two ideas have been embraced by governments for decades, really starting from 1980 onwards, and have been reflected in dietary guidelines since then. As a population, we have dutifully done as we have been told and dropped our overall fat consumption, aided eagerly by the low-fat food industry juggernaut around us. The problem is that neither statement is true and we can see the devastating consequences of this failed nutritional experiment all around us.
Why do we think that fat is trying to kill us?
Humans have been nourished by diets rich in natural fats for millennia, and some traditional cultures continue to eat in this way, with none of the chronic illnesses like diabetes and heart disease that we see in modern western populations. In the early part of the 20th century there was a surge in heart disease in America primarily affecting middle aged men (including President Eisenhower who had a heart attack in the 1950’s). The middle aged men running the country and the middle aged men running the scientific and medical establishments were desperate to figure out what was causing this surge in heart disease as quickly as possible*. Step forward the single individual who has probably had the greatest (and most damaging) impact on our understanding of nutrition: Dr Ancel Keys. Dr Keys was an American scientist who strongly believed that fats (and in particular saturated fats) were the root cause of heart disease. In order to prove this, he set out to collect data from multiple countries to show that the level of fat intake in a country was correlated with the level of heart disease. Keys had terrible data with extremely flawed scientific methods (for example, his study excluded France which was known to have low rates of heart disease but a love of traditional high fat food) but what Keys also had was hubris, charisma and powerful political connections. Through force of will, rather than sound science, his advice about reducing dietary fat and in particular saturated fat was adopted by the American Heart Association and the US Government, and began to spread internationally.
So, as a population we turned our back on the way that human civilisations have been eating for millennia essentially because some American guy told us to! We will look at the truth regarding the connection between (saturated) fat and heart disease in more detail in a separate post.
Fat does NOT make you fat
The idea that eating fat makes you fat is perhaps the foremost zombie idea in nutrition and it simply refuses to die. It originates from the discredited energy balance model of weight gain (calories in = calories out) which I have written about in a previous post. Of the three macronutrients both carbohydrate and protein contain 4 calories per gram. Fat on the other has contains over double the amount of energy at 9 calories per gram. The logic therefore goes that if you eat more fat, you are eating more energy, creating an energy surplus and the excess energy must then be stored as fat in the body.
If that were the case, we would expect to see that obesity rates in the UK dropped when our levels of fat consumption dropped from 1980 onwards. As everyone knows, the converse is true, since 1980 the rates of obesity in this country have trebled and over 25% of adults are now living with obesity, despite us buying in to this low fat doctrine. But why let the facts and the data get in the way of the theory?
There is no basis in science for the idea that fat makes you fat. We are not machines, we are animals and there is no sensor in the body for the amount of calories we eat. However, our hormones are sensitive to the type of food we eat. The primary hormone to think about in relation to weight gain and fat storage is Insulin. Of the three macronutrients carbohydrate is the one that stimulates insulin production (and therefore fat storage) the most, protein stimulates it to a small extent and fat does not affect it. Dietary fat is in fact the least likely macronutrient to trigger us to store energy as body fat. As we can see, the switch away from natural fats to refined carbohydrates in our diets has been disastrous for the population, and is a key driver of the global epidemic in type 2 diabetes. Yet, this idea refuses to die, perhaps only because of the simple quirk that we refer to both fat, the macronutrient, and body fat (“adipose tissue”) with the same word! More cynically, adherence to the unscientific calorie balance/low-fat paradigm provides a means for the processed food and beverage industry to exonerate itself and instead blame the obesity epidemic on individual greed/laziness/both.
Re-familiarise yourself with fats
Eating fat does not make you fat. If you are focused on losing weight, this is critical, and it is essential that you unlearn the myths about fat and weight gain that we have been brought up on.
However, there is far more to fat that just weight loss/gain. What about overall health, including heart disease? In this regard the type of fat that you eat is incredibly important. The bad news is that not all fats are healthy. The good news is that it is easy to work out which ones are healthy and which ones are not. In simple terms, stick to those “natural fats” provided by nature that have been eaten for centuries – think full fat yoghurt and dairy, extra virgin olive oil, butter, ghee, lard. Avoid processed (anyone spotting a theme?) or industrial fats – such as vegetable oils (especially if heated), margarine, fat found in processed food (often high in harmful trans fats/partially hydrogenated fats).
In order to stick to any dietary pattern, the food needs to be tasty, enjoyable and filling. Deprivation combined with willpower will only last you so long. Dietary fat is delicious and helps with satiety. Just think of the transformative effect of adding a large dollop of butter onto a plate of green vegetables. If you stick to healthy natural fats, adding more fat into your diet is an important tool in your armoury when trying to lose weight, reverse diabetes or just stay healthy.
*it was mainly due to smoking
Dr Neel Gupta August 2023
Further Reading