In recent years, large companies and foundations such as the American Heart Association, the National Institute of Health, and even the Academy of Nutrition and Dietetics have preached that high-fat diets contribute or even result in a variety of diseases. This has led to recommendations from practitioners and alike that it is important to consume a diet low in fat in order to maintain a healthy cardiovascular system (1,2) and body composition(3). However, it is important to note that there is a large discrepancy in the research in what constitutes a “high fat” diet. For instance, most animal models that induce obesity or disease tend to give a “high fat” diet that is also high in carbohydrates (4,5) Thus, it is important for us to understand that a “high fat” ketogenic diet is also a low carbohydrate diet. Understanding that, we can then answer the question: does fat make you fat?
The Traditional Western Diet
As a society, we are well aware that the combination of high fat and high carbohydrate can cause issues (i.e fast-food chains, some candies, etc). Throughout the decades there have been some brave pioneers who have gone against the status quo and sought answers in determining how low carbohydrate ketogenic diet fairs against a low fat for improving health markers (6,7,8). Still, the thought of trying to lose fat while eating high amounts of fat seems counterintuitive; however, there have been numerous studies demonstrating that a diet high in fat and low in carbohydrate does not necessarily result in weight gain. High-fat diets, such as the ketogenic diet, have been shown to have a profound effect on a number of health factors, with one of the most robust effects being weight loss (9). Several studies that have compared the ketogenic diet to a low-fat diet have demonstrated that a greater percentage of the weight loss in the ketogenic diet groups was fat mass and less was muscle mass which is ideally what everyone is hoping for (10,11,12,13). Often times people look at the number on the scale as the main indicator of success, but rather it’s the composition of that weight that really matters. These are some extremely audacious statements to be said about a diet that revolves around eating high amounts of fat. How in the world can you lose fat by eating fat? To be clear there are two types of fat we are going to discuss; dietary fat, and adipose (fat) tissue. In this article, we are going to look into some of the science and research that explains how eating dietary fat does not cause adipose tissue storage.
The Relationship Between Insulin and Fat Accumulation
In this day and age, it is no surprise that obesity is a major concern due to its direct correlation to serious medical illnesses (14). Time and time again, people have tried to find the end-all, be-all cure, but have tirelessly failed. What if I told you that a possible solution was hiding in plain sight and that we have been misleading about what to eat and how to eat it?
Research has been done in severely obese individuals who were 100 pounds overweight to try and find an explanation of how people get fat. What we have found is that it isn’t necessarily a result of over-eating or being sedentary, but rather a result of excess fat accumulation (15). As paradoxical as this sounds, it makes sense; prevent a person from accumulating fat, you prevent them from becoming obese. So then what regulates fat accumulation? Without exhausting you with a lesson on biochemistry, the answer, in short, may be insulin and insulin regulation (16). When you ingest carbohydrates your body responds by releasing insulin. This hormone shuttles nutrients such as glucose and free fatty acids into the cell. Simple carbohydrates exhibit a greater insulin release, thus creating an over-secretion of insulin over time when carbohydrates are consumed in abundant amounts. This abuse of insulin leads to a condition known as insulin resistance, meaning that the body is no longer receptive to the same amount of insulin it was before and therefore more insulin is needed to manage the carbohydrates we eat. This vicious cycle leads to the accumulation of more circulating insulin and glucose in the bloodstream.
The Relationship Between Glucose and Lipolysis
With all of this readily available glucose/sludge sitting around in our bodies (or street), our bodies shut off a process known as lipolysis, or fat breakdown, thus leading to the continuous storage of fatty acids in adipose tissue. Furthermore, these factors can lead to the birth of numerous chronic diseases such as diabetes mellitus or even metabolic syndrome.
Where this has been found to become another major problem is the effects glucose and insulin have on fatty acid oxidation. In the past, it has been the common conception that fat burns in a flame of carbohydrates. The notion of fats burning in a carb flame is called the glucose-fatty acid cycle, where glucose competes with fatty acids for energy substrate. One of the underlying principles of becoming keto-adapted is to cut off your body’s dependency on carbohydrates.
This hypothesis was questioned in the lab where scientists found the opposite. Instead of competing for oxidation, carbohydrates (glucose and/or insulin) actually directly inhibited fatty acid oxidation (17). Meaning that by ingesting carbohydrates you stop the metabolism of fat. This happens because glucose oxidation inhibits the transport of long-chain fatty acids into the mitochondria and doesn’t allow them to become oxidized(18). The intracellular availability of glucose determines which substrate is oxidized. In a non-keto adapted person, the presence of glucose will shift the cell to use carbohydrates for fuel over fats – resulting in an increased deposition of fatty acids. If you are not using dietary fat for energy, then you are storing it.
So, Does Eating Fat Make You Fat?
So what does all this mean? Everything you’ve heard about eating a “high fat” diet might not make as much sense now. The research above has provided us with insight into what happens when we eat carbs, but what about just fat? When we sever our body’s reliance on carbs, we still need to draw energy elsewhere. This is where the fat comes in! Under conditions of carbohydrate restriction, we learn to utilize this other form of energy. In a meal full of fat without carbs, we see that there is virtually no spike in insulin levels (unless consumed in very high amounts) (19). Without insulin fat is not stored within the cell to the same degree, rather it is broken down via lipolysis in the absence of glucose. Studies looking at fat oxidation in the presence of elevated glucose and insulin concluded that inhibition of CPT-1 (transporter required for long-chain fatty acid entry into the mitochondria) was a result of the increased blood glucose and insulin and led to a decrease in fat oxidation (20). This brings light to the fact that when we do not consume carbohydrates in conjunction with high-fat dieting, fat oxidation is not impaired.
Numerous studies have been done looking at low carb diets vs. low fat and for the most part, all had similar outcomes. The low carb groups typically lead to greater fat loss and better preservation of muscle (10,11,12,13).
In light of everything we have discussed here, we may be able to follow the notion that fat is not the determining factor for fat storage. Rather than a ‘fat’ problem, it is plausible that fat storage is a hormonal issue regulated by high carbohydrate intake and insulin/regulation. In the absence of carbohydrates, we do not see the same quantity of fat gained whereas carbohydrates alongside the consumption of fat can result in the storage of nutrients in adipose tissue. Studies suggest that this may be due to the insulin response from the intake of carbohydrates, not fat!
So, Does Eating Fat Make You Fat? No!
Eating carbohydrates causes a release of insulin, allowing the cell to take up nutrients for energy or storage.
When carbs are eaten in excess, the cells may become insulin resistant. This requires a greater amount of insulin to be released in order for the cell to be able to take up nutrients.
Insulin inhibits the oxidation of fat, causing fat to be stored rather than used for energy.
Dysregulation of insulin and glucose metabolism may be responsible for the storage of adipose tissue rather than the consumption of fat.
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