Fasting Framework

24-Hour Fasting: How It Works

A 24-hour fast spans a full day between meals—for example, dinner to dinner. It is a form of whole-day fasting rather than a daily time-restricted eating window.

Safety first: Intermittent fasting is not appropriate for everyone. Johns Hopkins advises checking with a clinician before starting and specifically cautions children and teens, pregnant or breastfeeding people, people with type 1 diabetes taking insulin, and people with a history of eating disorders. Seek medical guidance for medicines or conditions affected by food timing.

What a 24-hour fast changes

The defining feature is timing: a longer interval without caloric intake. It can reduce weekly energy intake, but the result depends on what happens across the rest of the week as well.

Evidence note. A 2025 BMJ network meta-analysis included 99 randomized trials involving 6,582 adults. It found broadly similar cardiometabolic benefits between intermittent-fasting strategies and continuous energy restriction, with relatively small differences among approaches. Long-term evidence remains more limited. Read the BMJ review.

Practical questions

People commonly ask about what breaks a fast, drinks, exercise and how to resume eating. Longer is not automatically better, and extending fasting beyond a planned approach can increase risk for some people.

Commercial approaches

Eat Stop Eat is one commercial program associated with periodic fasting. Our review separates the merchant's claims from broader evidence on intermittent fasting.

Last reviewed: September 2026. Educational information only; not medical advice.