Maintaining a ketogenic diet over six weeks or more was linked with improvements in mood, energy and anxiety, researchers discovered.
The findings point to an important new direction for research into treatment options for those living with the condition, experts say.
The research team highlights further studies are needed to explore any potential effects in a larger group of patients.
Energy source
The ketogenic diet involves significantly reducing intake of carbohydrates, like bread and rice. These are replaced by large amounts of fats, found in foods like butter and avocado.
Without carbohydrates the body begins to break down fat to produce chemicals called ketones which can be used for fuel, in a process called ketosis.
The ketogenic diet has been used in the treatment of epilepsy for more than a century and its benefits are now being studied across a range of psychiatric and neurological conditions.
Symptom improvement
The study involved 27 patients with a bipolar disorder diagnosis who followed a ketogenic diet for six to eight weeks.
Some 20 participants completed the study, demonstrating that the intervention was safe and tolerable in this population, experts say. Most patients reached and maintained ketosis during the study, with 91 per cent of their readings testing positive for blood ketones.
Among participants who provided reliable daily ketone and mental health assessments, increased ketone level was correlated with improvements in mood, energy, impulsivity, and anxiety.
Brain imaging also revealed reductions in excitatory neurotransmitters – chemical messengers in the brain – in two key brain areas implicated in bipolar disorder, suggesting a potential mechanism behind a ketogenic diet's effectiveness.
Metabolic benefits
Participants’ metabolic function also improved. Some 19 participants lost an average of 4.2kg (9.3lbs) and saw improvements in body mass index (BMI) and blood pressure.
The findings suggest that a ketogenic diet may help to mitigate common metabolic health risks associated with bipolar disorder, such as diabetes and heart disease, which can lead to shortened life spans, experts say.