Is a low-carbohydrate or ketogenic diet good for longevity?

Reviews point to interesting mechanisms: a ketogenic diet influences pathways that play a role in ageing¹. But a second review immediately tempers the enthusiasm: effects differ greatly depending on the disease and the dietary variant, and hard evidence that such a diet genuinely extends lifespan in humans simply does not yet exist².

The strongest evidence concerns weight and metabolism. Ketogenic diets demonstrably help with weight management, metabolic syndrome and insulin resistance³. The so-called Spanish ketogenic Mediterranean diet showed strong improvements in metabolic markers, with the added benefits of muscle preservation and reduced hunger. Whether those improvements also lead to a longer lifespan has never been demonstrated.

There are also risks. A high protein intake, typical of this diet, increases the load on the kidney filters. This is called hyperfiltration, and over the long term it can cause chronic kidney damage, even in the absence of pre-existing kidney disease⁴. Animal protein appears to be more harmful in this regard than plant protein. Long-term studies in humans are still lacking.

In specific diseases the picture is mixed. In cancer, everything depends on the tumour type and there is no consensus⁵. In Alzheimer's disease, the diet restored memory in mice, possibly via a specific ketone compound, but this has not yet been translated to humans⁶. In multiple sclerosis, small pilot studies found the diet to be safe, but evidence of effectiveness in humans is lacking⁷.

If you combine a ketogenic diet with intensive exercise, there is a concrete disadvantage. During high-intensity training, such as CrossFit, a high-carbohydrate diet performs better⁸. Since intensive exercise is itself one of the most powerful protectors of a long, healthy life, this is a practically important point.