Ketogenic Diet May Improve Metabolic Health More Than Other Diets

A wide range of diets can support weight loss for people who are overweight or living with obesity, so anyone focused solely on losing weight has several approaches available.

Research also indicates that some dietary patterns may provide health advantages that extend beyond weight reduction.

What has been less certain is how well widely followed diets compare for these additional effects, particularly their ability to improve obesity-related cardiometabolic problems such as elevated blood fats, fatty liver disease and prediabetes.

A new study in Cell Metabolism examined which of three diets frequently recommended for obesity could have the greatest overall effect on metabolic health.

“Diets can be dramatically different – high-fat, high-carb, and everything in between,” endocrinologist and study first author Max Petersen, of Washington University in St. Louis, told ScienceAlert.

“We wanted to know if the macronutrients in a diet modify the metabolic benefits of weight loss.”

Comparing ketogenic, Mediterranean and low-fat diets

Petersen and his colleagues ran a clinical trial involving 42 adults with obesity, prediabetes and excess liver fat.

Participants were randomly allocated to one of three dietary groups: a very low-carbohydrate ketogenic diet, a Mediterranean diet, or a very low-fat diet that was largely plant-based.

All participants received their full daily provision of meals and snacks, tailored to the diet they had been assigned.

The keto group could choose from a broad menu that included egg salad, pulled pork, and chicken with asparagus.

Those following the Mediterranean diet ate meals such as oatmeal with almonds and blueberries, quinoa with black beans and corn, and chicken pesto pasta.

The low-fat, plant-forward plan included fruit smoothies, vegetable tortilla wraps, and mixed grains with salmon.

On average, participants stayed on their assigned programme for about five months, continuing until they had lost roughly 10 percent of their starting body weight.

By this standard, every diet was effective: all participants reached the 10 percent weight-loss goal.

Ketogenic diet effects on liver health and prediabetes

However, blood tests and other assessments indicated that one diet produced the strongest metabolic-health improvements overall, especially for measures of liver health.

“We were very interested to see that several aspects of liver health improved most on the ketogenic diet,” Petersen told ScienceAlert.

“If just one aspect of liver health had improved, it wouldn't have been as compelling. But we saw improvements in liver fat, liver insulin sensitivity, liver fat production, liver glucose production, and other outcomes that all pointed to a uniquely beneficial effect of the ketogenic diet on liver health.”

Liver insulin sensitivity improved across all three groups, but the improvement among keto participants was two to three times greater. They also had the largest reduction in liver fat: 67 percent, compared with 45 percent on each of the other two diets.

The ketogenic diet’s impact on prediabetes was more striking still.

Half of the keto group achieved prediabetes remission, versus 29 percent of the Mediterranean-diet group and only 7 percent of those on the low-fat diet.

The team had anticipated that weight loss would improve insulin sensitivity and reduce liver-fat levels, but they had not expected such substantial effects in the ketogenic-diet group.

This was particularly notable because fats supplied 73 percent of calories in the keto diet, considerably more than the 35 percent and 15 percent provided by the Mediterranean and low-fat diets, respectively.

“We were surprised that in our participants with metabolically unhealthy obesity, the ketogenic diet did not cause harmful effects on blood cholesterol profiles,” Petersen said.

“Instead, cardiovascular risk factors tended to improve even on the high-saturated fat ketogenic diet.”

The researchers propose that the extremely low carbohydrate intake in the studied keto group, which accounted for only 4 percent of total calories, may keep circulating glucose and insulin levels low. This could reduce the liver’s creation of new fat while encouraging the breakdown of fat already stored there.

Important limits of the study

This was a small study, however. The researchers acknowledge that its limited sample size may have meant some differences between the diet groups were not detected; larger future studies may be able to identify them.

It is also unknown whether other, less restrictive low-carbohydrate diets that do not induce ketosis would produce the same metabolic benefits.

Even so, these findings offer several reasons why people who are overweight or have obesity may wish to consider keto for weight loss, as it appears to bring a range of metabolic-health benefits.

Anyone thinking about doing so should investigate the diet carefully and understand what it involves.

“A ketogenic diet is very different from a standard Western or American diet,” Petersen said.

“The amount of carbohydrate restriction needed to be ketogenic is quite severe. Most people understand that foods like bread and pasta contain carbs, but may not know that carbs are present in many other foods, including foods generally recognized as healthy such as starchy vegetables, fruits, and legumes.”

The findings are reported in Cell Metabolism.

This article was fact-checked by Fiona MacDonald and edited by Fiona MacDonald. Although we take pride in our process, we are only human. If you notice an error, please let us know.