How fasting burns fat
The metabolic switch: from sugar to fat in about 12–16 hours.
Key points
- After a meal, insulin rises and tells your body to store energy. Fasting lets insulin fall — that's the signal to release stored fat.
- For the first ~12 hours you mostly burn liver glycogen. As it runs low, fatty acids and ketones become your main fuel — the “metabolic switch”.
- Ketones aren't just fuel: they act as signals that reduce inflammation and support brain function.
- Time-restricted eating (e.g. 16:8) reduces weight, insulin resistance and blood pressure in controlled trials — even without counting calories.
- Total calories still matter. Fasting works best when your eating window isn't a free-for-all.
de Cabo & Mattson, NEJM 2019; Anton et al., Obesity 2018; Sutton et al., Cell Metab 2018.
Hunger Wave provides general educational information based on published research. It is not medical advice and does not replace a consultation with a healthcare professional. Stop fasting and seek help if you feel unwell.
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