Fasting and timing
Intermittent Fasting: 16:8, 5:2 and OMAD Compared
Intermittent fasting (IF) controls when you eat rather than what you eat. Research suggests it works mainly because it makes it easier to eat fewer calories, and results are similar to conventional calorie restriction for many people.
The main schedules
- 16:8: fast for 16 hours, eat within an 8-hour window, for example noon to 8 pm.
- 5:2: eat normally five days a week and cut to about 500-600 kcal on two non-consecutive days.
- Alternate-day fasting: alternate normal days with very low-calorie days.
- OMAD (one meal a day): a single large meal; hard to sustain and easy to under-eat protein.
What the evidence says
Trials generally find intermittent fasting produces weight loss comparable to daily calorie restriction. Some people also see improvements in blood sugar and blood pressure, mostly tied to the weight lost. It is a tool for adherence, not a metabolic shortcut.
How to start
Begin with a 12-hour overnight fast and extend gradually. During fasting hours, drink water, black coffee or unsweetened tea. When you eat, prioritize protein, fiber and whole foods so you stay full.
Who should avoid fasting
Anyone under 18, pregnant or breastfeeding, with a history of eating disorders, underweight, or taking medication for diabetes or blood pressure should speak with a clinician first. Stop if you feel dizzy, faint or unwell.
A 16:8 sample day
- 12:00: grain bowl with chicken, vegetables and olive oil.
- 16:00: Greek yogurt with fruit and nuts.
- 19:30: baked fish, potatoes and green beans. Kitchen closes at 20:00.
Frequently asked questions
Does fasting slow metabolism?
Short fasts do not meaningfully slow metabolism. Very aggressive restriction over long periods can.
Can I exercise while fasting?
Light to moderate exercise is fine for most people. For hard training, schedule workouts near your eating window.
Is intermittent fasting better than counting calories?
Not necessarily. Choose whichever approach you can follow consistently.
This article is for general education and is not medical advice. Speak with a doctor or registered dietitian before starting a new diet, particularly if you have a medical condition, take medication, are pregnant or breastfeeding.