A ketogenic diet can improve metabolic health and has interesting mechanisms that may slow ageing, but there is no direct evidence that it makes people live longer. Safety risks to the kidneys from prolonged high protein intake are real and should not be ignored.
A low-carbohydrate or ketogenic diet is examined in several reviews for its potential effects on healthy ageing. A scoping review (PMID 39275194) describes promising mechanisms via molecular pathways such as mTORC1 and AMPK, which are involved in ageing. Another review (PMID 39488864) concludes, however, that the effects vary considerably by condition and by type of diet, and that the evidence remains limited. To date, there are no hard long-term data in humans demonstrating that a ketogenic diet actually promotes a longer life.
The evidence is strongest in the area of weight and metabolism. An overview study (PMID 33920973) shows that ketogenic diets are effective for weight management and for addressing metabolic syndrome, insulin resistance, and associated risk factors. The so-called Spanish Ketogenic Mediterranean Diet (SKMD) showed strong improvements across all measured metabolic markers. Preservation of muscle mass and suppression of appetite are additional benefits that are mentioned. Whether this also leads to a longer lifespan, however, has not been demonstrated.
There are also safety risks to take into account. Ketogenic diets are often accompanied by a high protein intake. This can put a strain on the kidneys through increased pressure in the kidney filters (so-called hyperfiltration), with a potential risk of chronic kidney disease with long-term use, even in people without pre-existing kidney conditions (PMID 32669325). Animal protein appears to be more harmful in this regard than plant protein. Long-term research is still lacking.
For specific conditions, the results are mixed or preliminary. In cancer, the effects are highly dependent on the type of cancer and there is no consensus (PMID 38147966). In Alzheimer's disease, a ketogenic diet restored memory function in a mouse model, possibly via the ketone body beta-hydroxybutyrate (BHB), but this has not yet been translated to humans (PMID 38366025). In multiple sclerosis, there are small pilot studies in humans that find the diet safe and feasible, but evidence of effectiveness is lacking (PMID 27239035).
For athletes engaged in high-intensity exercise, such as CrossFit, a ketogenic diet offers no demonstrated advantage. On the contrary: high-carbohydrate diets appeared to perform better in that context (PMID 40471841). This is an important consideration for people who want to combine a ketogenic diet with intensive exercise, which is itself beneficial for a long and healthy life.
All claims are based on reviews, scoping reviews, and animal models. There are no large randomised long-term trials in humans measuring lifespan as an endpoint. The evidence for short-term metabolic benefits is reasonable, but for longevity specifically it remains limited and associative.