Ketogenic diets appear no more effective at improving glycaemic control or weight loss than other diets used in type 2 diabetes management over the long term, according to a systematic review and meta-analysis.

Researchers reviewed 19 reports from 11 randomised controlled trials, which assessed the effects of the low-carbohydrate diet on 541 adults collectively with T2D from Australia, the US, the UK, South Africa and Europe over two years.

Trials with intervention durations shorter than 14 days were excluded to ensure sufficient time for the ketogenic diet to induce ketosis.

Participants were, on average, obese, with baseline mean BMIs ranging from 33.1 to 38.9 kg/m² and body weight between 91.5 to 118.6 kg, noted the researchers, from the University of Hong Kong and Swinburne University, Melbourne.

Compared to the control, the ketogenic diet showed no significant difference in changes in glycaemic control or body weight, but greater increases in HDL (standardised mean difference 0.19; moderate-quality evidence) and greater reductions in triglycerides (standardised mean difference -0.41; low-quality evidence).

There were no significant differences in the change in diastolic blood pressure between the ketogenic diet group and controls at all follow-up time points, while for systolic blood pressure, significantly greater reductions were observed at 3-6 months follow-up only (very low-quality evidence) but only for six of the studies.

Further, among the studies which reported changes in renal function markers, all suggested that the ketogenic diet did not have any significant impact on serum creatinine, urinary albumin and eGFR (moderate quality evidence).

The researchers concluded that concerns regarding the impact of the ketogenic diet on cardiovascular disease risk and hepatic and renal function may be unfounded, while short-term data indicated the diet to be more effective than other diets in improving glycaemic control and inducing weight loss in the initial months.

“However, the ketogenic diet does not appear to confer substantial additional benefits for glycaemic control or weight loss compared to conventional diabetes diets over the long term,” they wrote in Diabetes & Metabolic Syndrome: Clinical Research & Reviews [link here].

“Although there is limited long-term safety data available, this should not discourage the use of the ketogenic diet for T2D management, as no evidence suggests any safety concerns associated with following the diet for an extended period.

They stressed regular monitoring of clinical parameters such as liver enzymes, renal  function markers and blood lipid profiles to minimise potential risks for patients.

Five studies were rated as having a high risk of bias. The inclusion of physical activity as a co-intervention in some studies might have also influenced results.