Ketogenic Diet and Cholesterol: A Meta-Analysis of 53 Randomized Trials

Ketogenic diets increased LDL cholesterol by an average of 8.22 mg/dL compared with control diets.

This increase was statistically significant.

LDL cholesterol is an important cardiovascular risk factor because LDL particles contribute to cholesterol accumulation within arterial walls and the development of atherosclerosis.

However, the increase varied between studies.

Subgroup analyses suggested larger LDL increases in trials involving participants aged 50 years or younger, those with a body mass index of 30 or below, and interventions lasting no longer than 12 weeks.

These findings suggest that the lipid response may depend partly on the population studied and the duration of the intervention.

However, subgroup results cannot reliably predict how any particular individual will respond.

The certainty of evidence for LDL cholesterol was rated low.

Across 51 randomized trials, ketogenic diets reduced triglycerides by an average of 22.31 mg/dL compared with control diets.

Triglycerides are fats circulating in the bloodstream. Elevated levels often accompany excess body fat, insulin resistance and other metabolic abnormalities.

Lower triglycerides may therefore represent a favorable metabolic change.

Subgroup analyses suggested greater reductions in trials involving participants with obesity.

However, results varied substantially between studies.

The prediction interval indicated that future studies could show considerably smaller reductions or even increases in triglycerides.

The certainty of evidence for triglycerides was rated moderate.

Across 49 randomized trials, ketogenic diets increased HDL cholesterol by an average of 3.52 mg/dL.

HDL cholesterol is commonly described as good cholesterol because HDL particles participate in cholesterol transport.

However, a higher HDL cholesterol concentration does not necessarily mean that cardiovascular risk has decreased.

The researchers found that the HDL increase tended to become smaller as intervention duration increased.

This association was identified through meta-regression.

It suggests that some early lipid changes may not remain equally pronounced over time.

However, the analysis does not establish that HDL cholesterol will necessarily decline in every individual who continues a ketogenic diet.

The certainty of evidence for HDL cholesterol was rated moderate.

Across 39 randomized trials, ketogenic diets increased total cholesterol by an average of 8.06 mg/dL.

The increase was statistically significant, although results differed considerably between studies.

Total cholesterol alone provides limited information about cardiovascular risk because it includes cholesterol carried by several types of lipoproteins.

For this reason, the increase in LDL cholesterol is particularly important when interpreting the findings.

The certainty of evidence for total cholesterol was rated low.

One clinically relevant finding emerged from studies classified by the researchers as involving healthy adults.

In this subgroup:

* LDL cholesterol increased by approximately 21.68 mg/dL across 6 trials. * Total cholesterol increased by approximately 25.38 mg/dL across 6 trials. * Triglycerides showed no statistically significant change across 7 trials.

These findings suggest that ketogenic diets may produce a less favorable cholesterol response in some adults without diagnosed metabolic disease.

However, these were subgroup analyses involving relatively few trials.

They do not establish that ketogenic diets are more harmful in healthy adults than in people with metabolic disorders.

Nor do they demonstrate an increase in cardiovascular events.

The results nevertheless highlight why changes in LDL cholesterol deserve attention even when a ketogenic diet is followed for general wellness rather than treatment of a diagnosed condition.