Evidence on ketogenic diets remains mixed across mental health, diabetes, and PCOS

Research into ketogenic diets is accelerating, but experts said current evidence remains limited for psychiatric disorders and diabetes, while a systematic review in overweight and obese women with polycystic ovary syndrome reported significant short-term improvements in metabolic, hormonal, and reproductive outcomes. Studies testing the role of the ketogenic diet on mental health conditions have been small, anecdotal, or pilot studies, and many did not include a control group of patients following a regular diet.

It is true that research into the effects of ketogenic and other diets on psychiatric disorders is accelerating. Twenty controlled clinical trials using the keto diet for severe mental illness are underway, with results of two trials set for publication within the next year. A University of California Los Angeles study investigating the effect of a keto diet on teenagers with bipolar disorder is still recruiting patients and will not be completed until March 2027, according to a posting on a federal website. At this point, it is premature, and there is not enough evidence to recommend a specific diet as a standalone, without medication such as antipsychotics or mood stabilizers.

Comments that diet can "cure" schizophrenia and diabetes and allow people to rid themselves of bipolar disorder diagnoses were described by researchers as overstating current evidence about the role that food can play in managing illness. In work published in 2019, two patients with schizophrenia experienced remission of their symptoms following a high-fat, low-carbohydrate ketogenic diet. The preferred word was "remission," not "cure." Patients with mental illness were urged not to stop medications on their own and not to try a ketogenic diet on their own as a treatment for schizophrenia or bipolar disorder.

On diabetes, type 1 diabetes, an autoimmune disorder, cannot be cured by diet alone. A healthy diet and exercise are keys to managing type 2 diabetes, but it can be difficult to use those tools alone to reverse the disorder.

In overweight and obese women with PCOS, a systematic review following PRISMA 2020 guidelines analyzed 14 studies involving 643 participants, including 240 from randomized controlled trials and 403 from observational or single-arm studies. The review included ketogenic diets of 50 g carbohydrates per day or less over 6-24 weeks. Most studies reported significant weight loss of 7-13% of baseline weight and reduced visceral adiposity. Marked improvements were observed in insulin sensitivity, with reductions in fasting insulin, glucose, and HOMA-IR.

Hormonal profiles improved, evidenced by decreased total and free testosterone, increased sex hormone-binding globulin, and normalization of the LH/FSH ratio. Reproductive benefits, including restored menstrual regularity and increased ovulation rates, were reported, although pregnancy outcomes were derived from small, uncontrolled cohorts and should be interpreted cautiously. Lipid profile changes were mixed but generally favorable, and adverse events were typically mild, though adherence challenges were noted.

Low-to-moderate certainty evidence suggests that ketogenic diets demonstrate significant short-term efficacy for improving weight, metabolic parameters, androgen excess, and reproductive function in overweight and obese women with PCOS. However, the evidence is limited by study heterogeneity, short durations, and varied protocols. Larger, long-term randomized controlled trials are needed to establish safety, sustainability, and optimal implementation.