Will Eating More Fat on a Ketogenic Diet Make People Fat?

Nowadays, thankfully, people are becoming increasingly aware that the low-fat era was one born under a false premise, yet there still seems to be a “fat phobia” lingering among the masses. To clear things up, remembering that “fat ingested does not equal fat stored” may help. This is along the lines of understanding that ingested protein does not automatically equal muscle growth.

In the metabolic state of ketosis, fat is the primary fuel source for the body, and the fat consumed contributes toward fuel for cellular function in much the same way carbohydrates act in glucose burning. Health issues associated with high-fat consumption are, more often than not, due to the combination of both high intakes of fat and carbohydrate, resembling a “Western Diet,” or “Standard American Diet (SAD),” both of which are commonly known to increase risks of obesity and insulin resistance. It is important that these should not be confused with the qualities associated with “good fats.”

How did this low-fat idea come to fruition?

In the 1950s, an American physiologist, Dr. Ancel Keys, hypothesized that consumption of saturated fat raises blood cholesterol levels and results in increased risk of myocardial infarct or heart attack. Over the years, dietary fat was pegged as the main underlying cause for not only heart attacks, but obesity. A new, low-fat food industry was created around the ideology that the “fat you eat is the fat you wear.” Ironically, in the same time that low-fat foods entered the market, the obesity-epidemic was born1—maybe fat was not the culprit after all?

If we only consider the energy-balance equation (i.e. calories in vs. calories out) then it is easy to see how removing dietary fat would be the solution, given that fat contains 9 calories per gram, whereas proteins and carbohydrates contain roughly 4 calories per gram. What is often overlooked, however, are the hormonal responses and satiety factors, among others, associated with consuming fats, carbohydrates, and protein. Of course, calories still matter; you can’t eat more than you burn on the ketogenic diet and continue to lose weight, but it’s time to get over the misconception that consumption of dietary fat leads directly to stored body fat, without considering the other factors at play.

How eating fat can lead to burning fat

There are many hormones governing our metabolism, but there is one master dietary hormone, and that is insulin. Insulin is released from the beta cells of the pancreas in the presence of glucose (i.e. carbohydrates) to shuttle it away from the blood and into the cells, which lowers blood sugar levels. Insulin is also responsible for telling our cells, “Hey everyone! Glucose is available! There’s no need to breakdown fat for fuel; let’s save that for later!” In the body, carbohydrates are the primary instigator of insulin release, whereas protein only causes a very mild release, and fat causes almost no response.

When glucose levels are significantly lowered, such as that achieved with a ketogenic diet, insulin requirements are also reduced. In the absence of insulin, cells can use stored fat for fuel, either directly (e.g. free fatty acids) or indirectly via the generation of ketone bodies (i.e. ketogenesis). Think of insulin as the gatekeeper of fat metabolism: When insulin is present, the gates are closed and fat is trapped inside the cell; when insulin is absent, the gates are open and fat can be broken down for fuel.

Keeping your hunger in check on the ketogenic diet

Besides suppressing insulin levels, the ketogenic diet is said to be very satiating, suggesting better management and control of the appetite. It can be argued that eating a ketogenic diet allows one to be more in tune with the body’s natural hunger signals. Furthermore, weight loss associated with the ketogenic diet is more often due to the natural calorie deficit that accompanies the diet since the ketogenic diet, by nature, has an appetite-suppressing effect.

Leave the rollercoasters for the kids!

A carbohydrate-based meal often produces a rapid postprandial rise and fall in blood glucose that leaves you searching for more food soon after eating. This happens because of the dependence on glucose for fuel, and when glucose is missing from the bloodstream, it sends the signals to the body that you need food now, sending you to the kitchen. It is almost like being controlled by glucose!

Following a ketogenic diet circumvents this glucose/insulin rollercoaster in two ways:

  1. Limiting dietary carbohydrates limits the rise and fall of glucose in the blood, which can trick the body into feeling hungry even in the fed state.
  2. The state of ketosis provides the cells with ketones, an alternative fuel source. Ketones are made from stored body fat in the absence of food. This fuel is almost always available since you’re wearing it!

The ketogenic diet offers other beneficial effects in addition to weight loss such as sustained energy throughout the day. This could contribute to increased endurance, for example, having the stamina to go to the gym even after a long day at work. Having the capacity to exercise could be an indirect effect of ketosis that could certainly have a favorable impact on weight loss.

The whole “fat makes you fat” myth is just that: a myth.


  1. La Berge, AF. 2008. How the Ideology of Low Fat Conquered America. J Hist Med Allied Sci. 63(2):139–177.


This content is not intended as a substitute for professional medical advice, diagnosis, or treatment. Individuals should always consult with their healthcare professional for advice on medical issues.

Submitted by the Metagenics Marketing Team

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