How long have you been fasting?
Enter when you last ate and choose any fasting target you like. Your timer will keep running even after you leave this page.
You have been fasting for
What may happen during a fast
Your body does not switch between fasting stages at exact times. These milestones are rough guides and can vary with your last meal, activity, health, metabolism and usual diet.
Digesting your last meal
Your body is still absorbing nutrients and mainly using energy from the food you recently ate.
Moving towards stored energy
Insulin generally begins to fall and your body gradually relies more on stored glucose between meals.
Fat use may increase
As stored liver glycogen declines, your body may begin using a greater proportion of fat for energy.
Ketone production may rise
The liver may produce more ketones from fat. The timing and amount differ considerably between people.
Prolonged fasting
Fasting-related metabolic changes may continue, but longer is not automatically better and the risk of side effects also increases.
These stages are general estimates, not medical measurements. Claims that processes such as autophagy begin at one exact hour cannot be reliably confirmed by a home fasting timer.
Does the timer keep running if I close the page?
Yes. Your start time and target are stored in your browser, so the timer can continue when you return on the same device.
Can I drink during a fast?
Staying hydrated is important. What counts as breaking a fast depends on your reason for fasting and the advice you are following.
Who should get medical advice before fasting?
Speak to a healthcare professional before fasting if you use diabetes medication, are pregnant or breastfeeding, have a history of an eating disorder, are underweight, or have a medical condition affected by food or fluid intake.
Does black coffee break a fast?
Plain black coffee contains very few calories and is commonly used during fasting. Milk, cream, sugar and flavoured syrups add calories and may affect the fast.
Can I exercise while fasting?
Light or moderate activity may be manageable, but stop if you feel dizzy, weak or unwell. Longer or more demanding exercise may require extra care.
Will fasting automatically cause weight loss?
Not necessarily. Fasting may make it easier to eat fewer calories, but weight loss still depends largely on your overall calorie intake over time.
How should I break a fast?
Eat slowly and begin with a normal-sized meal containing foods you tolerate well. After a short fast, there is usually no need for a special meal.