Low-fat vs keto
Interesting for a positive energy balance are now both extreme cases: for one we have a diet that consists almost entirely of carbohydrates, the low-fat diet, as well as the opposite case, in which virtually no carbohydrates are consumed, the ketogenic diet.
With the strict low-fat diet, the fat intake is kept as low as possible. Although the blood sugar and consequently also the insulin levels rise, but since the carbohydrates are used primarily for direct energy production and the fat content is quite low, only a few fat calories can get into the fat deposits. Especially since fat has its other functions (hormones, structures), those take priority to fat deposits (see above), which is why body fat deposits are lower in this case. This does not mean that unlimited carbohydrates can be consumed here, because the total energy balance must also be taken into account.
Of course, not all carbohydrates of direct energy production are supplied in an excess of energy. Although a large part still migrates into the glycogen deposits of the body, even here a too large supply remains. This remaining supply is stored in the fat deposits. However, a 1:1 conversion is not possible, since the carbohydrates must first be converted from the body to fat. However, energy is needed for this process so that some of the carbohydrates are still burned. This process is also called “de novo lipogenesis”.
However, in recent years, contrary to the traditional hypothesis of a carbohydrate heavy diet, it has been attempted to demonstrate empirically that de novo lipogenesis of carbohydrates under normal human consumption conditions is not an essential metabolic pathway. Carbohydrates are then converted to fat in humans (unlike other species, such as pigs) only when they consume more than 500 g of carbohydrate per day for several days. Ultimately, scientists today are of divided opinion on this topic.
The process is different with a ketogenic diet. In the low-fat diet, when trying to prevent the build-up of body fat by not adding fat, the strategy in a ketogenic diet is to prevent this by not releasing any insulin. Of course, carbohydrates are also consumed in a ketogenic diet, but this amount is so low that it no longer has any significant impact on insulin production. For example, Atkins, one of the founders of this diet, recommends consuming only 20g of carbs per day in some cases.
However, there is insulin secretion of course, but the body is missing the carbohydrate induced fluctuations in insulin secretion and in its place there are uniformly low levels. This situation also promotes growth hormone secretion and, in turn, fat burning and muscle building.
In the ketogenic diet, energy is not produced by burning carbohydrates, but the energy is extracted from so-called ketone bodies, which are a fission product of fatty acids.
Usually, an athlete will not practice either or both extremes of these two diets, or if so, then only for a short period of time, for example, in a fat loss diet. Especially the ketogenic nutrition strategies are very controversial as a permanent diet, not only for bodybuilders. Ultimately, they have not been able to prove that either of the two extremes are more effective, let alone healthier, in the long run. On the contrary, I believe, when it comes to building muscle, the lack of insulin leads to less frequent anabolic states. Therefore this diet is (in my opinion) indeed certainly ineffective, compared to one with an at least moderate amount of carbohydrates.