“What do you mean, ‘you can eat a high fat diet and lose weight’? Doesn’t eating fat make you fat?” If you’ve been ketogenic, or even if you’ve toyed with the idea of starting a ketogenic diet, you have likely heard someone in your life say something quite similar to this. Heck… you may have even heard someone ask you this when they became curious why you didn’t want a bun with your burger. We know we have! So, does fat really make you fat? Well the answer isn’t quite as simple as yes or no… it really never seems to be. But if we were to over simplify the scenario, the answer is, “No. Fat doesn’t make you fat.” But how can that be so? I mean… it’s in the name for crying out loud! Well, it has to do with the complexities of the human body and its metabolism of different macronutrients/substrates.
When discussing a ketogenic diet, you’ll hear that it is a high fat diet, and this is true. But “high fat” is really a relative term. It is called this because fat is meant to make up the highest percentage of your diet vs protein or carbohydrates. When compared to how you may have been eating prior to starting keto, you may not be eating more grams of fat. That’s not the case for everyone, but it seems to be for many. By eating primarily fat and drastically reducing your carbohydrate intake (to 20 net grams per day or less) you start to train your body to rely on fats as its primary fuel source. This is an indiscriminant process that causes your body to utilize ingested fats (fat you eat), stored fats (adipose/body fat), and self-generated fats (cholesterol). This can result in a number of health benefits for most people but the primary health benefit we will discuss here is the benefit of weight reduction through the reduction of adipose tissue (body fat).
Unlike carbohydrates and proteins, lipids (fats) have an exceptionally hard time going through the metabolic process known as gluconeogenesis. This is the process of converting non-glucose/non-carbohydrate molecules into glucose to undergo glycolysis for the production of energy in the body1. Instead, lipids go through a process known as lipolysis. This breakdown takes a bit longer and actually yields more energy which is part of the reason why a single gram of fat has a higher calorie content than a single gram of carb or protein. It’s all about the energy! Your body is even smart enough to start doing this with your own fat stores when your caloric intake is low enough… particularly when there is no glucose coming into the body.
So what does that mean to you? Well, it means you will be hard pressed to find yourself in a situation in which your body is able to or willing to convert fat into glucose. Without doing that vital step, it cannot store it for energy to be used later because your skeletal muscles and adipose tissue are made to take up glycogen (a byproduct of glucose) for storage, not lipids (fats). That said, because your adipose tissue cannot take up fat to be stored for use later, it cannot make you fat! This is somewhat of an over-simplification of the process, but that is the foundation of the ketogenic diet and why it is so successful in helping thousands of people control their body weight in a healthy and sustainable way (as well as a number of other health benefits).
If this is true, why is it we all believe fat makes us fat? There are a number of reasons for this. Perhaps the biggest reason is simply the terminology we use when discussing food such as “fatty foods” implying it either makes you fat or contains a large amount of fat or both. However, society itself has played a major role in this as well. Many of us have grown up in households or have parents who grew up in households that used to cook with a lot more fat than they do now. But much of that changed in the 1970’s when the US Government made a national recommendation based on limited, poorly understood (or misunderstood), and ill-obtained research done by a man named Ancel Keys starting in the 1950’s. This research was far from complete or truly representative of the risks dietary fat intake played in everyday life/health, but without any better evidence available, this was all the US Government had to go on.
Food Will Win the War- Don’t Waste it !
Vintage WWI ad for Crisco 1918
Marketing campaigns around the late 1970’s started to imply you were unpatriotic, unhealthy, and un-American if you didn’t eat vegetable oils/margarine or other animal fat substitutes. This was incredibly effective and employed in a time where being patriotic was important to nearly all Americans. So what did we do? We trusted that we were given the right information and we did what we were told. We ate low fat, we introduced more processed and unhealthy fats, in their place, drastically increased our carbohydrate consumption and refined sugar consumption, and we got fatter and fatter and fatter. We began to develop more diabetes, more inflammatory disorders, more neuro-cognitive disorders2 … we became the poster-children for unhealthy living. But with all of this being the case, the recommendations still haven’t been changed. Sure, we’re now seeing recommendations to cut out sugar, but sugar goes by many names. Sugar also isn’t the only carbohydrate source that breaks down to glycogen or that causes a spike in your blood glucose and insulin levels.
And now for the positive spin...fat is not only good for you, but it provides more energy per gram than carbohydrates. Did you know that fats provide 9 calories per gram versus just 4 calories per gram when compared to carbohydrates? That means that you are getting more than two times the amount of energy from fats as you are from carbohydrates! This also means you fell more satiated with fats than you do with carbohydrates. When you are satiated, you feel less hunger and generally consume fewer calories which aides in weight loss. This applies to everyone, whether you are ketogenic or not. The science that determines the energy provided by carbohydrates and fats is not affected by which metabolic process your body is utilizing. So one stands to wonder why fats are given such a bad reputation when not only do they not make you fat, they can help you to eat less because they you feel satiated longer.
As noted above, sugar stores as fat. Sugar makes us fat. Fat, on the other hand, does not. We need to learn to change the way we think about foods, the way we talk about foods, and we need to start to better research the impact of food on our overall health and chronic/preventable diseases. Until we do, the Standard American Diet will remain a S.A.D. excuse for a way of eating.
1. Sampaolo, M. (2017, June 12). Gluconeogenesis | biochemistry. Retrieved June 12, 2018, from:https://www.britannica.com/science/gluconeogenesis
2. Klonoff, D. C. (2009). The Increasing Incidence of Diabetes in the 21st Century. Journal ofDiabetes Science and Technology(Online), 3(1), 1–2.