Dietary changes are often an initial approach to support healthy weight loss, as modifying food choices and overall calorie intake can help create a sustainable energy deficit.
In particular, eating plans that emphasize nutrient-dense foods and appropriate portion sizes can support gradual and sustainable weight reduction.
Approaches such as the ketogenic (keto) diet may promote weight loss by substantially reducing carbohydrate intake and increasing fat intake, which can lead to reduced appetite and lower overall calorie consumption for some individuals.
These changes may also influence metabolic health in ways that extend beyond weight loss, such as lowering blood glucose (sugar) and insulin levels, and improving insulin sensitivity.
Now, a new study suggests that the keto diet may also provide greater improvements in liver fat and blood sugar regulation than other popular dietary plans for weight loss.
The study, published in Cell Metabolism, found that people with obesity, prediabetes, and fatty liver disease who followed a keto diet experienced greater improvements in several measures of metabolic health than participants following either a Mediterranean diet or a low-fat, plant-forward diet.
The findings suggest that the composition of a diet may influence metabolic health beyond the effects of weight loss alone.
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However, the study was small, involving just 42 participants, and the findings do not necessarily mean that a ketogenic diet is the best choice for everyone.
Estimates suggest that obesity affects roughly 40% of adults in the United States, and is associated with an increased risk of conditions, such as type 2 diabetes and fatty liver disease.
Dietary interventions are commonly recommended to help people lose weight. However, it has remained unclear whether one approach provides additional metabolic benefits beyond those associated with losing weight.
In this small study, researchers from Washington University School of Medicine enrolled 42 people with obesity, prediabetes, and fatty liver disease.
Participants were randomly assigned to follow one of three dietary plans:
The research team provided all participants with food and met with them weekly, alongside a dietitian, to support adherence.
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Researchers adjusted calorie intake so that participants in all three groups lost approximately 10% of their body weight, which took approximately 4 to 5 months.
“In people with obesity, prediabetes, and excess liver fat, moderate weight loss — 10%, or about 25 pounds on average — improved metabolic function whether it was achieved with a ketogenic, Mediterranean, or very-low-fat plant-forward diet,” lead author Max Petersen, MD, PhD, told Medical News Today.
“Many benefits, including improved muscle insulin sensitivity, were similar across diets. However, the ketogenic diet produced several additional metabolic benefits beyond those seen with weight loss alone, including greater reduction in liver fat content and improvement in liver insulin sensitivity.”
– Max Petersen, MD, PhD
All three diets were associated with reductions in body fat and improved insulin sensitivity, resulting in better blood sugar regulation. However, the ketogenic diet produced the largest reduction in liver fat.
Those following the ketogenic diet experienced an average 67% reduction in liver fat, compared with 45% reductions in both the Mediterranean and low-fat, plant-forward groups.
The ketogenic group also experienced the greatest increase in glucagon, a hormone that helps regulate blood sugar and promotes fat breakdown in the liver. They also had the largest reduction in circulating insulin levels.
“Blood insulin levels increase after a meal primarily in response to carbohydrate,” Petersen explained. “The ketogenic diet meals contained very little carbohydrate, so we were not surprised to see that insulin levels throughout the day were lower.”
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“There are probably two main reasons glucagon levels were higher in the ketogenic diet group: higher dietary protein content (amino acids stimulate glucagon release) and lower insulin levels (insulin suppresses glucagon release),” he added.
The researchers suggest that these changes could explain why the ketogenic diet produced greater improvements in liver fat.
“The ketogenic diet had a much greater effect on several metabolic factors that regulate liver fat than did the other two diets,” Petersen highlighted.
“The ketogenic diet caused a greater increase in blood glucagon concentration, which is a hormone that stimulates liver fat breakdown, and a greater decrease in blood glucose and insulin concentrations which stimulate liver fat production. So together these factors caused a greater reduction in the rate of production of liver fat from blood glucose.”
The differences were also apparent when researchers looked at participants’ prediabetes status following the intervention.
Around half of those in the ketogenic group no longer met the criteria for prediabetes after the weight-loss period, compared with 29% in the Mediterranean group and 7% in the low-fat, plant-forward group.
The researchers also reported that participants on the ketogenic diet did not experience an increase in blood fat or cholesterol levels despite consuming considerably more dietary fat than those in the other groups.
“Because the ketogenic meals contained very little carbohydrate, the increase in blood glucose after meals was much lower in the ketogenic diet group than the other diet groups,” Petersen noted.
“So it was not surprising that hemoglobin A1c, a test of average blood glucose, and fasting blood glucose improved most in the ketogenic diet group,” he told us.
The study findings suggest that dietary plans that reduce carbohydrate intake could have metabolic effects beyond those explained by weight loss alone, particularly in people with high liver fat and prediabetes.
Notably, these findings come at a time when medications that target GLP-1 pathways, such as Wegovy, Zepbound, and Foundayo, have substantially changed the treatment of obesity.
However, while these medications can produce significant weight loss, the study findings suggest that the composition of a person’s diet may also provide additional metabolic benefits.
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“The results from our study demonstrate that moderate weight loss induced by a ketogenic diet has greater therapeutic benefits, particularly on liver health, than matched weight loss induced by consuming a Mediterranean or very-low-fat plant-forward diet,” said Petersen.
“However, it is important to note that we provided all meals to our study participants to enhance compliance. Achieving compliance with any dietary guidance is difficult in a real world setting and remains the Achilles heal of diet therapy,” he concluded.
Still, the results need to be interpreted cautiously. The small trial included only 42 people and lasted around 4 to 5 months, so it cannot establish whether the observed benefits would persist over the long term.
Additionally, people may find a ketogenic diet difficult to maintain, as its high fat content, which can include large amount of saturated fat from animal products, may not be appropriate for everyone.
While promising, larger and longer-term clinical trials are necessary to determine whether these metabolic advantages can persist over time and whether they translate into fewer cases of health conditions, such as type 2 diabetes.
For now, the study adds to evidence that weight loss alone may not be the sole determinant of how diet affects metabolic health, suggesting that the balance of carbohydrates, fats, and other nutrients may also play an important role.
