Intermittent fasting works for weight loss. It does not work better than other approaches that reduce how much you eat, which is the claim that made it famous.
What the evidence shows
There are now a reasonable number of randomised trials comparing time-restricted eating and alternate-day approaches against ordinary continuous calorie reduction. The consistent finding is that when total intake is matched, the results are broadly similar. People lose comparable amounts of weight and see comparable changes in blood markers.
The claims about fasting doing something special to your metabolism, or triggering large amounts of cellular repair, come mostly from animal studies and short mechanistic work in humans. That research is genuinely interesting. It is not yet a reason to expect an advantage in your own body, which is why this sits at Grade B rather than A.
How much difference it makes
If you find it easier to eat nothing until midday than to eat slightly less at every meal, fasting will work better for you, and that is a real and legitimate advantage. Adherence is the thing that decides whether any dietary change succeeds, and different people adhere to different structures.
If skipping breakfast makes you ravenous by two o’clock and you eat more overall, it will fail, and no amount of theory will rescue it.
What to do
If you want to try it, the 16:8 pattern, eating within an eight hour window, is the easiest to sustain and the most studied. Give it three or four weeks before judging. Keep protein intake up and keep training, or a meaningful part of what you lose will be muscle.
Cautions
Do not fast if you are pregnant or breastfeeding, if you are under 18, or if you have a history of an eating disorder. In that last case, structured restriction can reactivate patterns that took a long time to settle, and the risk is not worth it.
If you take medication for diabetes, particularly insulin or a sulfonylurea, do not change your eating pattern without speaking to your prescriber first. Fasting while on these can cause dangerous hypoglycaemia. This is not a minor caution.
Medicines that must be taken with food need their timing rethought if you compress your eating window. Ask your pharmacist.
When to see a doctor
If you are losing weight without trying, that is not a success and it needs investigating.