Does the fasting-mimicking diet, such as Prolon, actually work?

Three cycles of five fasting days per month reduced body weight, body fat mass, blood pressure and a growth factor linked to ageing (IGF-1) in a randomised study of 100 healthy participants. The largest effects were seen in people who already had elevated values. No serious adverse effects were reported.

The same cycles were associated in a secondary analysis with a reduction in biological age of 2.5 years on average, less fat in the liver and a more favourable immune profile. An important caveat: these are biomarkers. Whether this also means you stay healthy longer or get sick less is not something these studies can tell us.

In cancer patients, early clinical studies show that FMD can be safely combined with standard treatments and that it lowers blood sugar and growth factors. In breast cancer patients and in animal research into colorectal cancer there are indications of enhanced anti-tumour immunity, but a genuine survival benefit in humans has not yet been demonstrated. Those larger studies are still ongoing.

There is a serious caveat regarding all of the above results: virtually all published data come from research groups with direct financial interests in L-Nutra, the company behind ProLon. Independent replication of the results by other research groups is scarce. That does not mean the results are incorrect, but it calls for extra caution when interpreting them.