While following a ketogenic diet, which consists of getting almost all your calories from fat and very little from carbs, can help you lose weight, it can also damage your gut microbiome and clog your arteries.
Also known as the keto diet, this way of eating forces the body to use alternative fuel. It begins to rely on ketone bodies, a form of fuel that the liver makes from stored fat, rather than glucose from carbohydrates, which causes weight loss.
Studies in the past have compared the health outcomes of individuals who follow a ketogenic diet to those who do not, suggesting that there may be disadvantages as well as benefits.
The best type of medical evidence has now been conducted by Javier Gonzalez and his colleagues at the University of Bath in the United Kingdom through a randomized controlled experiment. The researchers gathered 53 participants with an average age of 34; none of them were obese. About one-third of the participants were randomly randomized to follow a ketogenic diet that consisted primarily of fat intake (more than 70%) and less than 8% of all carbohydrates.
Another third were instructed to follow a low-sugar diet in which their fat intake was limited to 35 percent and free sugars to 45 percent, while their intake of “free” sugars, a form of carbohydrates, can be found in foods such as are syrups, cakes and biscuits, they account for five percent of their total calorie intake.
The remaining third consumed small amounts of free sugars, accounting for slightly less than 20% of their total caloric intake. In contrast, they consumed roughly 30% and 35% of their energy from unhealthy sugars, carbohydrates and fat, respectively. The control group consisted of these individuals. The range of protein consumption in each diet was 15% to 18%.
X-rays taken a month later showed that those on the ketogenic diet lost an average of 1.6 kg of fat. By testing the amount of ketone bodies in the individuals’ blood, urine and breath, the team was able to determine that they were following a ketogenic diet. Dietary adherence was also measured through food diaries.
People who ate a low-sugar diet lost an average of 1 kg of fat, but people who ate a normal diet lost no weight. The researchers found—inconclusively at first—that the subjects’ weight loss was due to calorie restriction rather than increased exercise by having the motion trackers on and off for varying amounts of time.
Although the ketogenic group lost more weight than the control group, their levels of low-density lipoprotein (LDL), or “bad” cholesterol, were 16% higher. In addition, their levels of apolipoprotein B, a protein that clogs arteries and increases the risk of heart attacks, were 26% higher. Unlike subjects in the control group, those on the low-sugar diet experienced a 10% drop in LDL cholesterol and no change in apolipoprotein B levels.
In addition, the researchers found that subjects following a ketogenic diet only had lower levels of Bifidobacterium, a form of gut flora associated with a stronger immune system that helps produce B vitamins, compared to those on a low-sugar diet. . According to Gonzalez, this is most likely because people on a low-carb diet consumed less fiber, which increases bifidobacteria levels.
But it’s not certain whether the ketogenic diet harms the gut microbiome, because it’s not clear what the full effects of bifidobacteria are or what defines an ideal diet, according to Natasha Schoeler of Great Ormond Street Hospital in London.
Furthermore, according to Schoeler, elevated cholesterol levels are not always dangerous if they fall below critical thresholds, although elevated apolipoprotein B is problematic.
According to Schoeler, long-term studies are needed to determine whether the benefits of the ketogenic diet for weight loss outweigh the potential risks to gut health and cholesterol in obese individuals.
According to Schoeler, dieting is ultimately the biggest obstacle to weight loss for those who are obese or overweight. “Whether it’s a normal carb diet but with fewer calories, or the same amount of calories with less carbs — if you stick to it, you’ll generally lose weight,” she says.
