Intermittent fasting for weight loss: what the evidence says
Intermittent fasting can help some people eat less, and research suggests it works about as well as a typical low-calorie diet. It isn't magic, it isn't necessary, and it isn't for everyone.
Not medical advice. Fasting is not right for everyone. If you are under 18, pregnant or breastfeeding, have a history of disordered eating, or have a medical condition (especially diabetes or anything involving medication), talk to a doctor before fasting. Read the full safety page.
What the evidence says
- Comparable to other diets. Mayo Clinic: "Research suggests that alternate-day fasting is about as effective as a typical low-calorie diet for weight loss."
- Calories still matter. Mayo Clinic: eating fewer calories than you expend remains the basis for losing weight.
- Long-term effects are unclear. There is little long-term research, so long-term benefits and risks are unknown.
- Some studies show weight loss. Johns Hopkins Medicine cites small studies in which adults with obesity lost weight, and advises checking with a doctor first.
What to expect
Hunger, tiredness and headaches are common side effects, and Mayo Clinic notes most go away within a month. Watch the trend of your weight over weeks rather than any single weigh-in, since day-to-day readings move around.
Where walking fits
Fasting changes when you eat. Walking changes how much you move. They are separate levers and you can use either without the other. StepFast tracks both so you can see what's happening. Read walking for weight loss or walking while fasting.