One of the most common things you hear from advocates of low carb diets is this:
“Become a fat burner rather than a carb burner to lose fat!”
Low-carb gurus like to promote the idea that by eating their special low-carb, high-fat diet, you can magically coax your body into the elusive state of “fat burning” that will “cause your body fat to vanish right before your very eyes.”
“Be a fat burner instead of a sugar burner… You will have amazing energy… Incredible physical and mental performance…No crashes…and you will burn off all your body fat in days!”
Or so they say…
First let me acknowledge the part of all this nonsense that’s actually true: Becoming fat-adapted so that you’re burning predominately fat rather than carbohydrate for fuel is actually a real thing. So that part is actually true. It is indeed possible to train your body to rely primarily on fat rather than carbs for fuel.
And, it’s actually very simple to do it: All you have to do is eat a low carb, high fat diet.
Don’t eat many carbs, and eat lots of fat, then BOOM! After a few weeks, you are now fat adapted, and your body will primarily rely on fats rather than carbs for fuel.
Now that you’ve switched out a large portion of carbohydrate calories for fat calories and made yourself into a “fat burner,” you can expect lots of fat loss, right?
This was the conclusion from the latest 2014 meta-analysis (i.e., data from a non-cherry-picked comprehensive review of the scientific studies) on the subject: “There is probably little or no difference in weight loss and changes in cardiovascular risk factors up to two years of follow-up when overweight and obese adults, with or without type 2 diabetes, are randomized to low CHO (low-carb) diets and isoenergetic balance (higher-carb diets that are equal in calories).” [i]
In other words, looking at all these different studies that compared people on equal calorie low-carb and higher-carb diets, they were not able to detect any difference whatsoever in either health measures or fat loss.
So is this meta-analysis telling us something novel? Not really. As it turns out, there are dozens of studies that have found this conclusion, going back several decades.
Numerous studies have compared low-carb diets to higher-carb diets. In metabolic ward studies (Grey and Kipnis, [ii] Golay et al.,[iii] Miyashita et al.,[iv] Stimnson et al.,[v] and Naude et al.[vi]), researchers consistently find no difference in fat loss between those on low-carb and high-carb diets.
Even when we compare higher-carb diets to extremely low-carbohydrate diets, we see the same thing: as long as protein intake and calories are controlled, there is no difference in fat loss between high- and low-carb diets.
- A relatively recent trial examined the effects of three diets consisting of roughly 1400 kcals each day for twelve weeks. The diets had the following macronutrient proportions: a) very low fat and high carb (70% carb), b) moderate carb (50% carb), and c) very low carb (4% carb). What did they find? There were no differences in fat loss between the groups. [vii]
- Another recent trial compared two 1500-calorie diets, a moderate carbohydrate diet (40% carbohydrate) and a very low-carb ketogenic diet (a tiny 5% carbohydrate). The researchers concluded that the “diets were equally effective in reducing body weight and insulin resistance, but the ketogenic low-carb diet was associated with several adverse metabolic and emotional effects.”[viii] In other words, going low carb did not accomplish any additional fat loss—all it did was make people feel worse.
- Grey and Kipnis (1971) studied ten obese patients who were fed 1,500 liquid-formula diets containing either 72% or 0% carbohydrate for four weeks before switching to the other diet. Despite massive differences in insulin levels, participants lost the same amount of weight each week regardless of whether they ate the high-carbohydrate diet or the zero-carbohydrate diet. [ix]
These studies make it abundantly clear that there is simply no validity to the claims that carbohydrates or insulin have some unique fattening effect that’s different from any other calorie source like fat.
As long as calories haven’t changed, high-carb, low-fat diets and low-carb, high-fat diets cause—get ready for it—absolutely no difference in fat loss. None.
The bottom line is this: Eat 1,500 calories while on a high-carb low-fat diet, and eat 1,500 calories on a high-fat low-carb diet, and you’ll lose the exact same amount of body fat.
So yeah, you can eat a low-carb high-fat diet and make yourself into a “fat burner” …
Here’s the big problem: Being a “fat burner” (by eating a low-carb diet) has absolutely NOTHING to do with burning fat off your body!
You become a “fat burner” because fat–not carbs–is the predominant fuel you’re eating, not because you’re burning more fat off your BODY!
You’re burning all that butter, cream, oil, and animal fat you ate that day–NOT fat from your body.
Countless studies have proven that when matched for calories, low carb eating “fat burners” have…the EXACT SAME rate of fat loss as carb burners.
Let me repeat that: Exactly the same amount of fat loss.
What’s the Take-Home Message?
Don’t fall for this “fat burner” scam from low-carb gurus who intentionally try to get you to confuse “burning fat” by eating a low-carb high-fat diet with burning BODY FAT.
These two kinds of “fat burning” are completely unrelated. You don’t burn off more body fat by eating a low-carb, high-fat diet. You just burn all the fat you’re eating every day.
[iii] Golay A, et al. (1996). Similar weight loss with low or high carbohydrate diets. Am J Clin Nutr. 63:174-8.