Losing Weight: Cut Fats or Carbohydrates?

Surely, one of the questions that most people create confusion when losing the “love” is to whether lowering carbohydrates or fats…

It is true that reducing carbohydrates, significant weight loss occurs by glycogen and retained water. Alongside this, we are better insulin sensitivity and reduced inflammation (factor of great importance in obese).

However a few weeks ago, a study was published showing how to trim fat gave better result than cutting crabs , which had only been observed in long – term studies and never for metabolic effect, but by adherence to the diet. Obviously, this statement has caused a stir in social networks questioning if they really cut carbohydrates can be valuable for Losing Weight. Therefore, I decided to write an article about it, so that you can understand how nutrition there is no absolute truth.

Understanding the Study

The first thing we see when looking at the methodology of the study, is a small sample (n = 19), consisting of 10 men and 9 women with a similar percentage of fat (39.3%). The subjects were divided into two groups according to the diet consumed first (high or low carb), although both have the same diet “base” during the first 5 days with a distribution of 50% carbohydrates, 35% fat and 15% protein .

The approach would be as follows:


As we can see, he followed a diet based on both groups, followed by a high carbohydrate diet (diet 6d RF) or high fat (RC diet 6d). Later diets are exchanged with a period of washout of 2-4 weeks to avoid possible adaptations. Both diets would have the same caloric intake, with a deficit of 30% compared to the common starter diet (ecologic Baseline Diet).


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The composition of the diets was as follows:


Something I quite liked the time to see the methodology, is that both the high fat diet (Diet RC) as the high carbohydrate (RF Diet) had the same caloric and protein intake. This is of great importance, since in many studies low carbohydrate diets provide a greater amount of protein, obtaining better results.

Regarding calories, protocols “ad libitum” which becomes “eat until you’re hungry” are used. In that case, the low – carb diets tend to be more satiable, consuming fewer calories and thus more Losing Weight than a low-fat. Having these two controlled factors, the result wins veracity.



One of the parameters used when measuring the impact of both diets was breathing coefficient (RQ), where a value of 1.0 tells us that we primarily use carbohydrates as an energy source and 0.7 we use fats. What you get is the following:

The group consuming a diet high in carbohydrates did not change the energy substrate, while the group with high fat diet reduced their RQ, reflecting greater use of fatty acids as an energy source. However, I would like to clarify that this phenomenon is normal:

When our glucose intake is reduced, our body launches a series of mechanisms to save glucose we have, such as increased insulin sensitivity in the short term, gluconeogenesis or an increase of FAT / CD36 (transporters of fatty acids )

Thus, we can say that our body uses more fat as an energy source when we restrict carbohydrates, but these fatty acids are not our body reserves, if not of our diet (avocado, olive oil, nuts … etc).

This my hypothesis is shared by the authors of the study, which argue that same conditions calories / protein diet, restricting carbohydrates or fats have the same impact on body fat almost, in fact, it is seen as fat foods during a diet high in carbohydrates only provide 8% of energy, which gives us a 92% to oxidize glucose and body fat.


Despite being a studio with a pretty good methodology, we can find some buts, as they can be:

Small group of subjects, needing at least a sample of 30 people.

Intervention limited time, requiring several weeks to see noticeable changes

Small fluctuations with DXA, where sensitivity is 400g minimum and fluctuations affect water balance.

Using simulation models, increasing the likelihood of error when comparing results.

On a personal note, I would have liked that the group with high-fat diet had a lower intake of carbohydrates to 70g instead of 140g they consumed.

In short, we can see how a diet high in carbohydrates is also effective in losing weight. However, the scenario that we are in real life is far from the one shown in this study, in which food intake (and therefore macronutrients) was controlled.

The problem we found is the associate fast carbohydrates, foods high in sugar and with a high palatability, leaving food side as tubers, fruit, vegetables or vegetables…

For that reason, seeks more grip diet that you think, forget burn carbs or fats and focus on eating well. It is the only way to find long – term results.

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