A very low-carbohydrate ketogenic diet yields greater improvements in liver health and blood sugar control than high-carbohydrate or Mediterranean diet plans, even when all three diets result in identical amounts of weight loss, according to a randomized clinical trial published August 27 in Cell Metabolism.
Clinical Trial Compares Three Diets for Obesity and Liver Health
Researchers at Washington University School of Medicine in St. Louis randomly assigned 55 adults with metabolically unhealthy obesity—characterized by prediabetes and fatty liver disease—to follow one of three specific nutritional plans for roughly five months. According to the study, participants received 100% of their food throughout the research period and attended weekly meetings with a study dietitian to maintain strict adherence.
The trial evaluated a low-carbohydrate, high-fat ketogenic diet; a high-carbohydrate, low-fat, plant-forward diet; and a Mediterranean diet balanced between the two extremes. Across all three intervention arms, individuals lost an equal amount of weight, dropping about 10% of their total starting weight. Muscle insulin sensitivity also improved by roughly 50% from baseline across all groups.
“All three diets—despite vastly different macronutrient makeups, from very low carbohydrates to very high carbohydrates—successfully improved metabolic health through weight loss alone,” said Samuel Klein, MD, the Danforth Professor of Medicine and Nutritional Science at WashU Medicine and senior author of the study, as reported by WashU Medicine.
Ketogenic Diet Delivers Superior Liver Fat Reduction
While general weight loss proved sufficient to restore muscle insulin sensitivity, liver health outcomes diverged significantly across the nutritional plans. WashU Medicine researchers discovered that insulin sensitivity in liver cells improved two to three times more on the ketogenic diet compared with the Mediterranean and high-carbohydrate plans.
Did you know? Petersen, MD, PhD, assistant professor of medicine at WashU Medicine.
Furthermore, the very low-carbohydrate ketogenic diet reduced fat inside the liver by 67%, compared to a 45% reduction observed in the other two diet groups after the five-month period. “Our study shows that for people with obesity and fatty liver disease, a low-carbohydrate ketogenic diet could help reduce that statistic,” Petersen noted in the findings.
Blood Sugar Control and Prediabetes Reversal
Blood glucose regulation also showed marked differences depending on macronutrient distribution. The ketogenic diet lowered 24-hour blood glucose measurements by 20% from baseline, compared to an 8% reduction on the alternative plans.
Daily blood insulin levels dropped by 74% on the low-carbohydrate diet, versus 44% on the Mediterranean diet and 27% on the high-carbohydrate diet. This drop reflects a decreased physiological demand for insulin when consuming very few carbohydrates, sparing the pancreas from overproducing the hormone. Consequently, half of the participants assigned to the ketogenic diet reversed their prediabetes, compared to 29% on the Mediterranean diet and 7% on the high-carbohydrate diet.
“Many metabolically unhealthy patients also are candidates for GLP-1 medicines, which have been very useful tools for helping people lose weight,” Petersen stated in the published findings. “But our results show that choice of diet remains important because it has an impact on specific health outcomes that go beyond weight loss alone.”
Frequently Asked Questions
What were the three diets tested in the WashU study?
Researchers tested a low-carbohydrate high-fat ketogenic diet, a high-carbohydrate low-fat plant-forward diet, and a Mediterranean diet balanced between the two.
Did all diets result in weight loss?
Yes. Participants across all three groups lost an equal amount of weight, shedding about 10% of their total starting weight over the course of five months.
How did the ketogenic diet improve liver health?
The ketogenic diet reduced intrahepatic fat by 67% and improved liver cell insulin sensitivity two to three times more than the other diet plans.
Who funded this research?
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