The ketogenic diet increases cholesterol levels while aiding in weight loss.

A low-carbohydrate ketogenic diet is linked to higher cholesterol levels but also more significant fat reduction when compared to a low-sugar diet.

A ketogenic diet can help you lose weight, but it can also harm your gut microbiota and clog your arteries. It involves getting virtually all of your calories from fat and very little from carbohydrates.

The body is forced to use an alternate fuel by following this eating plan, often known as the keto diet. It starts to depend less on glucose from carbohydrates and more on ketone bodies, a type of fuel the liver produces from stored fat. Previous research comparing the health results of those on a ketogenic diet to those of people not on one has revealed potential disadvantages in addition to benefits.

Javier Gonzalez and colleagues at the University of Bath in the UK have now carried out the best kind of medical proof using a randomized controlled experiment. The researchers recruited 53 volunteers, who had an average age of 34; none of them were obese. About one-third of the subjects were assigned at random to a ketogenic diet, which was characterized by a high consumption of fat (more than 70%) and a low intake of carbs (less than 8%).

One-third more were told to adhere to a low-sugar diet, which allowed them to consume only five percent of their total calories from "free" sugars, a type of carbohydrate that can be found in foods like syrups, cakes, and biscuits. Their intake of fat and non-free sugar carbohydrates was limited to 35 and 45 percent, respectively.

Less than 20% of the total calories ingested by the remaining third came from tiny amounts of free sugars. On the other hand, non-free sugar carbs and fats accounted for about 30% and 35% of their calorie intake, respectively. These were the members of the control group. Each diet's protein intake ranged from 15% to 18%.

A month later, X-rays revealed that people on the ketogenic diet had lost an average of 1.6 kg of fat. Through measurements of ketone bodies in the subjects' breath, urine, and blood, the researchers were able to ascertain that the subjects had followed the ketogenic diet. Food diaries were another tool used to gauge diet adherence.

A low-sugar diet caused participants to gain an average of 1 kg of fat, while a regular diet caused no weight reduction. By having the individuals wear activity trackers on and off for varying periods, the researchers discovered—unclearly at first—that the subjects' weight loss was attributable to calorie restriction rather than increased exercise.

Despite losing more weight than the control group, the ketogenic group had 16% higher levels of low-density lipoprotein (LDL), or "bad" cholesterol. Moreover, they had 26% higher levels of apolipoprotein B, a protein that clogs arteries and raises the risk of heart-related events. Those on a low-sugar diet had a 10% reduction in LDL cholesterol and no change in apolipoprotein B levels compared to those in the control group.

Furthermore, compared to those on a moderate-sugar diet, the researchers found that those on the ketogenic diet only had decreased levels of Bifidobacterium, a kind of gut flora linked to a stronger immune system and which helps in the manufacturing of B vitamins. Gonzalez speculates that this is most likely because low-carb diet participants ingested less fiber, which increases Bifidobacteria levels.

According to Natasha Schoeler of Great Ormond Street Hospital in London, it's unclear what constitutes an optimal diet or the full effects of Bifidobacteria, therefore it's unclear whether a ketogenic diet harms the gut flora. Furthermore, even if elevated apolipoprotein B is undesirable, Schoeler claims that elevated cholesterol levels are not always dangerous if they fall below essential limits.

Long-term research is required, according to Schoeler, to determine whether the benefits of a ketogenic diet for weight loss outweigh any possible concerns to gut health and cholesterol in obese people.

According to Schoeler, the largest barrier to weight loss for people who are obese or overweight is sticking to a diet. "Generally speaking, if you follow a diet that is low in calories but high in carbohydrates, or vice versa, you will lose weight," the expert states.