Does a fasting-mimicking diet work better than simply eating less?

Ordinary calorie reduction is, to date, the best-supported dietary strategy for a longer and healthier life. This has been demonstrated robustly in animal and laboratory research, but how it plays out in humans over the long term has not yet been studied sufficiently.

A fasting-mimicking diet (FMD) and other forms of intermittent fasting also lead to weight loss and improvements in insulin sensitivity and other cardiovascular risk factors, both in people with a healthy weight and in those with excess weight. However, direct comparative studies are scarce. The limited head-to-head research that does exist shows no convincing or consistent advantage of FMD over simply eating less.

On one point, FMD does appear to work differently from continuous calorie reduction: it may stimulate stem cell regeneration and bring about lasting metabolic effects that are not seen with constant calorie restriction. However, this has so far only been demonstrated in animal research and has not yet been convincingly shown in humans.

When it comes to cancer prevention, both ordinary calorie reduction and FMD lower the activity of growth hormone and an associated growth factor (IGF-1). There are indications that the alternation between low and normal levels, as occurs with FMD, may be more beneficial than the continuously low levels seen with ongoing calorie restriction. In preclinical models, a combination with cancer therapy also looks promising, but large human studies are not yet available. Furthermore, a serious warning applies to cancer patients: fasting can cause or worsen malnutrition, and that risk carries significant weight.

In short: for weight loss and metabolic health, FMD and ordinary calorie reduction are probably comparably effective. Whether FMD offers genuine added value remains an open question for now. If you want to try it, discuss it with your doctor or dietitian, especially if you have a chronic condition.