Low-fat diet vs. low-carb diet: which is better for losing fat?
A new study [1] has apparently challenged everything we know about the subject!
In 2015, the journal “Cell Metabolism” published a study that should have changed the game. Why?
Because the findings of this study reported that, contrary to current belief, a low-fat diet can lead to greater body fat loss better than a low-carbohydrate diet.
Yet the findings of this study were – for one reason or another – ignored! Why were they ignored?
Perhaps because this revelation didn’t sit well with low-carb advocates, and could jeopardize their entire arsenal of arguments.
How did the study go?
Scientists from the National Institutes of Health led by Dr Kevin Hall, recruited 19 obese men and confined them to a metabolic room for two weeks. Everything these volunteers ate was carefully measured and allocated.
During the first period (i.e. the first two weeks), the men had their calorie intake reduced by around 30% following carbohydrate-only restriction (low-carb diet).
In the second period (the following two weeks), the test conditions were reversed and the men switched to a low-fat diet. Caloric intake was maintained irrespective of the nutrient restricted (fat or carbohydrate).
At the same time, the researchers monitored the amount of body fat burned by the participants on a daily basis.
Study results: is the low-fat diet better?
Volunteers on a low-fat diet lost 89 grams per day of body fat, while those on a low-carb diet lost 53 grams per day.
And contrary to the stipulations of proponents of ketogenic diets, the researchers found that insulin played a limited, even insignificant role in the fat loss recorded.
Admittedly, the low-carbohydrate diet is generally less insulinogenic (and therefore results in more fat being burned). However, it was the low-fat diet that resulted in the greatest loss of body fat.
This finding calls into question the theory that high insulin production leads to less body fat loss and more body fat storage.
Interpretation and limitations of the study
There are two potential problems with this study.
Firstly, the number of participants was very small (just 19 volunteers). However, it has to be said that putting 19 obese people in a “metabolic kitchen”, where everything they eat is monitored, is an onerous process.
Secondly, the researchers made some mathematical projections on both the low-carb and low-fat dieters and attempted to calculate the outcome if the study was conducted over a 6-month period.
According to the predictive calculations, they concluded that following a low-fat diet over this period would have led to modestly better fat loss (around 3kg) than a low-carb diet.
“While the present study has demonstrated the theoretical possibility that isocaloric diets differing in carbohydrate and fat may result in different body fat losses, the body acts to minimize these differences.”
Therefore, and if you give any credence to this study (and you should), you should reconsider your position towards dietary carbohydrates.
Ultimately, what matters most for body fat loss (or gain) may well be what all the dietitians were stressing: Calories matter more than specific nutrients.
So the low-carb diet doesn’t work?
This study isn’t trying to suggest that the low-carb diet doesn’t work. And these researchers made it clear … that’s also the case for any diet where you’re asked to think about what you eat.
Yet we should be asking ourselves why this low-carb diet works, since the results of this study showed that insulin doesn’t play a decisive role in fat loss, at least when it comes to carbohydrates.
That said, this is not an invitation to underestimate the role of this substance. On the contrary, you should do your best to increase insulin sensitivity.
The more you do, the easier it will be to reduce your overall body fat, not to mention the other health benefits you’ll gain.
