A ketogenic diet may be more effective than a Mediterranean or low-fat plant-based diet for treating obesity, prediabetes and fatty liver disease, researchers say.
A study published on 27 August in Cell Metabolism found that about half of patients who followed a ketogenic diet no longer met the criteria for prediabetes by the end of the trial. Cell Metabolism is a peer-reviewed scientific journal that covers biology and medical research focusing on metabolic processes.
The ketogenic diet also improved liver health and markers of metabolic function more than the other two eating plans tested.
Prediabetes is a condition where blood sugar levels are higher than normal, but not yet high enough to be diagnosed as type 2 diabetes. Fatty liver disease involves a build up of excess fat in the organ, which can lead to inflammation and serious liver damage if left untreated.
Clinical trial setup
Researchers conducted the trial with 42 participants who had obesity, prediabetes and fatty liver disease.
The participants were randomly divided into three groups to follow either a ketogenic diet, a Mediterranean diet or a low-fat plant-based diet.
To ensure strict compliance, the research team provided all the meals for the participants. The patients also met with a nutritionist every week to help them adhere to their assigned eating plan.
The daily calorie intake was adjusted for each person with the goal of losing about 10 percent of their body weight over four to five months.
During the study, the ketogenic group received 73 percent of their calories from fat and just 4 percent from carbohydrates. Fat and carbohydrates, along with protein, are the primary macronutrients that provide the body with energy.
In the Mediterranean diet group, carbohydrates made up 50 percent of the calories and fat accounted for 35 percent.
The participants on the plant-based diet received 70 percent of their calories from carbohydrates and 15 percent from fat.
By the end of the study, all three diets had resulted in a significant reduction in body fat. The participants also showed greater insulin sensitivity, improving their ability to regulate blood sugar. Insulin is a hormone that helps cells absorb glucose from the bloodstream for energy.
Superior liver results
However, the ketogenic group showed the greatest improvement in various markers of liver and metabolic function.
Liver fat decreased by an average of 67 percent in the ketogenic group, compared to 45 percent in the other two groups.
Researchers said one of the most unexpected findings was that patients on the ketogenic diet did not show an increase in blood lipids or cholesterol, despite consuming the highest amount of fat. Blood lipids include cholesterol and triglycerides, and high levels are typically linked to an increased risk of heart disease.
The research team tracked the metabolic activity of each participant over a 24-hour period using repeated blood tests.
They found the ketogenic group had the largest increase in glucagon, a hormone that promotes the loss of fat from the liver. Glucagon works alongside insulin to maintain steady blood sugar levels by triggering the liver to release stored glucose.
This group also recorded the largest drop in blood insulin levels, which researchers said can also help reduce liver fat.
Prediabetes reversal
At the close of the trial, about 50 percent of the participants on the ketogenic diet no longer met the criteria for prediabetes.
In the Mediterranean diet group, 29 percent of participants reversed their prediabetes condition. Only 7 percent of the plant-based group achieved the same result.
According to nutritionists at Health Line, an online provider of health information, the ketogenic diet is designed to induce nutritional ketosis. Ketosis is a metabolic state where the body begins to draw more of its energy from burning fat rather than glucose.
The diet relies on high amounts of fat from sources like olive oil, avocados, nuts, seeds, fatty fish, eggs, butter and full-fat dairy products.
A typical ketogenic dietary breakdown involves 50 to 60 percent fat, 30 to 35 percent protein and 5 to 10 percent carbohydrates.
Long term challenges
While the new study shows the ketogenic diet can limit metabolic risk, dietitians warn that it is not suitable for everyone and can be difficult to maintain over the long term. A diet can only work if a person is able to follow it consistently.
The Mediterranean diet focuses on foods traditionally eaten in countries bordering the Mediterranean Sea, including fruit, vegetables, whole grains, nuts and legumes.
It features fewer ultra-processed foods and more minimally processed ingredients. Ultra-processed foods typically contain industrial ingredients, preservatives and artificial additives that are not used in home cooking.
Experts point out that the Mediterranean diet has the strongest and most tested scientific data for the long-term prevention of diabetes and cardiovascular disease. Cardiovascular disease encompasses conditions affecting the heart or blood vessels, such as heart attacks and strokes.
Because the Mediterranean approach is an overall eating pattern rather than a strict diet, it is often easier to maintain over time.
A plant-based diet also emphasises fruit, vegetables, whole grains and legumes. Unlike a strict vegan diet, it does not necessarily exclude all animal products, but meat is not the main ingredient in meals.
