Dietary Fat Can’t Make You Fat? Uh, Yeah it Can

The reaction of some when presented with facts!
The reaction of some when presented with facts…

As I’ve mentioned in the past, it’s quite amusing how nutritional paradigms shift so suddenly.

Dietary fat used to be evil. Now, dietary fat is heavenly and cannot make you fat. You are free to consume as much bacon and Kerrygold butter as you please, as it’s the carbohydrates and insulin that make you fat, not dietary fat itself.

By believing the above, you’re essentially giving objective evidence a big ‘ol “screw you, I’m going to believe what I want to believe, regardless of what the science says”. Unfortunately, people like this are far gone and cannot be saved from the dogma that is burying their critical thinking abilities.

Recently, Christine Cronau, a seemingly well-respected name in the Paleo and low carb community, has been spouting off the idea that fat cannot make one fat. She literally believes it to be impossible. You can check out her Facebook page here. Be careful, the science is scarce, and the sensationalism is abundant. Look, I’m sure Christine is a wonderful human being, and this post is not to bash, but rather to present correct information that is not misleading to the public.

When presented with evidence that contradicts her cherished ideals, she quickly busts out the infamous Facebook ban-hammer, blocking anyone who doesn’t believe in her nonsensical and wildly biased belief system. What’s even more amusing is that, to prove dietary fat cannot make you fat, she cites a bunch of studies showing that hypocaloric low carb diets lead to weight loss. Wait, creating a caloric deficit and sustaining it over a period of time leads to the loss of fat mass? Who knew

Not only does this do nothing to prove her “belief”, it shows her ineptitude in dealing with objective evidence. If one desired to prove the theory that dietary fat cannot make one fat, they would have to do an overfeeding experiment in which excess calories are coming from dietary fat. When I mentioned this to Christine, she blocked me and deleted all of my previous posts in the thread. By doing this, she confirms that critical thinking is discouraged in her realm of the universe. No, facts don’t matter, as she would rather build a community of sheep who share her confirmation bias, not daring to challenge any of the ideas or claims she puts forth. Sorry, this is a cult, not a community.

Anyhow, with that out of the way, I’m going to quickly explain how dietary fat is the macronutrient that is stored with the most efficiency, and it certainly can make you fat in the context of a positive energy balance.

How am I going to do this, you may be wondering? I’m going to cite scientific evidence that actually supports what I’m suggesting, not a compilation of studies that do nothing to prove my point or a bunch of blog posts that display a blinding confirmation bias. Maybe Christine should take her fingers out of her ears and look at the science for a change, she might learn a thing or two. Sadly, some are too invested in their bias that they cannot afford to admit they’re wrong about pretty much everything.

A Quick Note About Energy Balance

Regardless of macronutrient composition, if you’re in a negative energy balance, you lose weight (7). Period. Macronutrient composition is a factor, but energy balance is king.

So, studies that observe a hypocaloric scenario cannot be used to prove the notion that fat cannot make one fat, as nothing is inherently fattening in the context of a caloric deficit.

Just wanted to make that clear before we move forward.

How Fat Can Make You Fat

Amidst the misconception that carbohydrates and insulin are the main drivers of fat gain, and ultimately obesity, many have developed the belief that dietary fat plays no role in the accumulation of body fat. The assertion is that as long as insulin is low, you will not gain body fat. The first problem with this theory is that protein is a potent stimulator of insulin secretion, along with carbohydrates.  So if you wanted to completely avoid an insulin response, you would have to consume fat and only fat.

Of course, the above scenario is unrealistic, as is the premise that insulin must be kept low in order to avoid gaining body fat. The fact is that fat can be stored in the complete absence of a rise of insulin levels by acylation stimulating protein (1). The idea that insulin levels must be raised in order for body fat to be accumulated has been thoroughly debunked, yet for whatever reason, this “theory” is still the centerpiece of many nutrition arguments and hypotheses.

Overfeeding Experiments

One cannot discuss the fattening effects of specific macronutrients without the context of overfeeding. No caloric surplus, no fat gain. Luckily for those who care about the evidence, there have been experiments observing the effects of both carbohydrate and fat overfeeding, albeit over a relatively short period of time.

In a paper by Hill et al, researchers looked at the effects of two weeks of both carbohydrate and fat overfeeding (50% over maintenance caloric intake) after one week of consuming a baseline, weight maintaining diet (2). As a result of pure carbohydrate overfeeding, carbohydrate oxidation increased significantly, causing less fat to be burned. The researchers summed up fat gain due to carbohydrate overfeeding as follows: “…we conclude that positive fat balance was due to a decrease in fat oxidation accompanying the increase in carbohydrate oxidation.”

As a result of pure fat overfeeding, fat oxidation did not significantly increase, indicating that the excess dietary fat was preferentially stored rather than oxidized. Here’s a summary from the researchers: “…excess dietary fat is stored with a very high efficiency and the body does not acutely adjust to increased fat intake. If overeating occurs, more of the excess will end up as body fat if the excess is fat compared with carbohydrate.”

These findings are consistent with Lyle McDonald’s article titled “How We Get Fat“, in which he asserts that both carbohydrate and fat overfeeding lead to fat accumulation, but by different mechanisms. As the researchers alluded to above, dietary fat is preferentially stored as fat, and carbohydrate is preferentially oxidized or stored as glycogen, either in the liver or muscle tissue. Carbohydrate overfeeding leads to more carbohydrate oxidation and less fat oxidation, which means more dietary fat is stored, along with less stored body fat being released.

Dietary fat overfeeding leads to more direct fat storage.

So, both scenarios of overeating lead to fat accumulation. However, pure dietary fat overfeeding leads to more efficient fat storage due to little increase in fat oxidation in response to fat consumption.

In addition, de novo lipogenesis (the conversion of carbohydrate to fat) seems to be quantitatively insignificant, as demonstrated by the above paper by Hill et al, along with many others (3, 4, 5, 6).

I encourage those who are interested to take a look at this graphic of a passage written by researcher Marc Hellerstein, as he does a great job explaining the relevance of the conversion of carbohydrates to fat in humans (note: credit goes to CarbSane for providing this image in response to Christine Cronau’s nonsensical claims.

Some Clarifications and a Brief Summary

Before I go on, I want to make myself clear: I’m not recommending that someone eat a low-fat diet based upon the fact that dietary fat is preferentially and efficiently stored. Overeating of any kind will lead to fat accumulation. So, this post was to merely point out the fact that yes, dietary fat can easily make one fat. If fat loss is the goal, one needs to be in a caloric deficit. If one is in a caloric deficit, fat gain will not occur, regardless of macronutrient composition.

All diets should focus on personal preference and sustainability, first and foremost. If one prefers dietary fat over carbohydrates, then shift the diet more towards a higher fat intake. The reverse is true as well. But as always, you must be cognizant of caloric intake. If you don’t implement a caloric deficit (somehow, someway) you will not lose body fat.

The message that dietary fat cannot make you fat is one that can be damaging. This is evident by the failures of many Atkins dieters to lose weight. They replace carbohydrates with copious amounts of bacon, and if this causes them to reach or  exceed their maintenance caloric intake, they do not lose fat. Confusion, anxiety, and an overall sense of failure typically follows.

The advice should be clear from the beginning: calories count. Sure, fat can be satiating and cause a spontaneous reduction in overall caloric intake.  But what about when it doesn’t? What about those who still overeat on a low carbohydrate, high fat diet? If they are told from the beginning that calories are the main arbiter of weight loss, they will know where to make adjustments. If not, they won’t.

Don’t be fooled by the guruism.


Facebooktwittergoogle_plusredditpinterestlinkedinby feather


  1. Blair says

    I’m curious what you think of Sam Feltham’s double 21 day experiments where he maintained a caloric excess of either carbohydrates or fat. As far as n=1, that seems to highly favor a high fat diet.

    • Jake Johnson says

      Hey Blair,

      Thanks for the question.

      This is a topic that has been quite popular over the last few weeks, and I’ve even had a few exchanges with Sam on Twitter. I don’t think much of his experiment to be honest. First of all, the amount of nuts he consumed in the first experiment was pretty ridiculous, and who knows how many of those calories were actually absorbed. Second, he failed horribly to match protein between the two experiments, and of course, protein is the macronutrient with the highest thermic effect and has the largest impact on lean mass retention/building. In addition, he failed to specify exactly what his baseline diet was. I believe he said somewhere that it was around 30% carbohydrate. Dropping to very low carb from there could lead to water and glycogen losses and less bloat overall, which would certainly contribute to scale and waist measurements. And finally, his low fat, high carb experiment was not low fat at all (something like 130+ grams, if I recall correctly).

      So the point is, there are too many confounding variables to consider Sam’s experiment any kind of evidence. There is plenty of controlled research showing the lack of advantage of high fat, low carb diets when calories and protein are equated. Heck, even studies that weren’t conducted in a metabolic ward fail to show a difference in fat loss between the two diets.

      And finally, everyone knows eating 5,800 calories of junk food is bad for your health. Chronically overeating of any kind is bad for your health. Dr. Mark Haub conducted the n=1 Twinkie diet (consuming large amounts of junk food) but stayed in a caloric deficit, and he still lost weight, and his health markers improved. So, both quality and quantity matter. And macronutrient composition of the diet should be based upon personal preference rather than believing in an advantage (that doesn’t exist) for one diet over the other.

      Hope this answers your question.


  2. says

    Hey Jake,

    Great post, it’s nice to see people treading that fine line between total following of ‘science’ and going also with what they’ve learned from working with real people. It’s the space where real coaches get real results, where you have to play with the variables you’re given, not what you’d like to have, in some sort of perfect world.

    One thing that I find interesting about the low carb/carbs-are-bad issue is the anecdotal reports of people losing decent amounts of body fat whilst (seemingly) consuming very high levels of fat.

    One thing from my experiences with myself and my clients is the need to be aware of shifts in metabolism. Only recently, for reasons as yet unknown, I’ve seen an almost total shift in food preferences. From carb based and bugged by cravings to super low carb and only (but happily) desiring protein foods and low-carb veg. It’s proving quite a revelation to be asked ‘do you want some flapjack (or insert any other sweet food)?’ and find that I genuinely have no desire for it at all. Cravings gone, energy for endurance exercise up (I did a 2 1/2 hour hard bike ride round some local hills the other day and needed no sustenance whilst out!) and eating a diet super-high in nutrients. Making me very happy, that’s for sure.

    I guess it’s a bit like the difference between climate and weather; diet is what you give your body day by day, metabolism is what that looks like over the weeks, or something like that, but better explained!

    Keep up the good work,


  1. […] It’s crucial to check yourself. I do my best to remain open to most points of view, but there are times when I catch myself drifting a bit off track. We’re all human. But in order to grow and improve your knowledge base, you must be able to support your beliefs with scientific evidence and you must be able to withstand opposing viewpoints. If your beliefs are going unchallenged, you’re promoting a cult, not a community (like this individual). […]

Leave a Reply

Your email address will not be published. Required fields are marked *