Is intermittent fasting worth it?
Intermittent fasting helps with weight loss and improves blood glucose and insulin, but over the longer term it does no better than simply eating less. If the fasting structure helps you stick to it, it is worth it; do not expect additional health benefits that come for free.
Intermittent fasting works if you want to lose weight: all well-known variants produce a clinically meaningful reduction in body weight compared with unrestricted eating. Alternate-day fasting also shows somewhat greater weight loss than conventional caloric restriction in short-term studies, on average about 1.3 kg more. But that advantage disappears once studies last longer than 24 weeks. Beyond that point, intermittent fasting performs no better than simply eating less.
Fasting blood glucose and insulin fall with intermittent fasting. However, the measure doctors use for long-term blood sugar control (HbA1c) does not improve measurably more than with conventional caloric restriction. For most individual blood glucose outcomes, the quality of the evidence is low or very low.
The effect on blood fats depends on which fasting variant you choose. Alternate-day fasting lowers cholesterol and triglycerides. Time-restricted eating, consuming food within a limited daily time window, actually showed a slight rise in LDL cholesterol in some comparisons. The picture is therefore not positive for all variants.
A concrete drawback to keep in mind: intermittent fasting is associated with loss of muscle mass. That is relevant if you are somewhat older or already have little muscle mass. Adequate protein intake and strength training can partly limit that risk, although this was not specifically examined in the reviewed studies.
Whether intermittent fasting helps people live longer has not been demonstrated in humans. Indications for this come from animal research. Randomised studies in humans on long-term mortality or cardiovascular disease are virtually absent. For anyone considering intermittent fasting as a long-term health strategy: it can be an enjoyable way to eat less, but it is not a proven miracle solution that outperforms conventional caloric restriction.
Based on multiple systematic reviews and meta-analyses (PMID 40533200, 34919135, 37906749, 37828854, 38955141). Quality of evidence for individual outcomes is moderate to low; long-term studies are scarce.
Does a fasting-mimicking diet work better than simply eating less?
There is currently no convincing evidence that a fasting-mimicking diet works better than simply eating less. For weight loss and metabolic improvement, both strategies appear comparable; choose whichever you can sustain best.
Do antioxidant supplements make sense?
For healthy people, antioxidant supplements such as beta-carotene and vitamin E are not useful as protection against cancer or heart disease, and beta-carotene is frankly inadvisable for (ex-)smokers. The only well-supported exception is the AREDS formula for advanced macular degeneration: discuss this with your ophthalmologist.
How many years does smoking cost me, and does quitting still help?
Smoking demonstrably costs years of life expectancy at the population level, but a precise personal figure cannot be given on the basis of this research. Quitting always helps, at any age: the sooner you quit, the greater the gain.
Is taking extra vitamin C worthwhile?
Extra vitamin C offers little benefit for most people. Intensive athletes and people following a carnivore diet do have a good reason to supplement, and those who take it daily tend to experience slightly milder symptoms when they catch a cold.
Does fasting or intermittent fasting help prevent cancer?
There is no evidence that fasting prevents cancer in humans; the animal results are promising but contradictory. If you want to address excess weight as a way of reducing risk, intermittent fasting can be a tool for that, but do not expect a direct cancer-preventive effect.
Does fasting reset your immune system?
Fasting lowers inflammatory markers and improves metabolic risk factors, but a true 'reset' of the immune system has not yet been firmly demonstrated. The strongest gains are in weight and blood pressure; for specific immune diseases it is still too early for conclusions.