How to start intermittent fasting and pick your protocol
Intermittent fasting isn't a diet, it's a schedule. You pick a window to eat in, and the rest of the day you don't eat. What changes from protocol to protocol is the size of that window: 12 hours to get started, 8 hours in the classic 16/8, 4 in 20/4, a single meal on OMAD, or two light days a week on 5:2.
The most common mistake is going too hard too soon. This guide takes it in order: first a 12/12 you'll barely notice, then 16/8, and only if that's going well, the advanced protocols. It also covers the practical calls: skip breakfast or skip dinner? Every day? What about eating out?
The essentials in 5 points
- Start with 12/12 for a week: dinner at 9 p.m., breakfast at 9 a.m. Almost nobody notices.
- Move up to 14/10, then 16/8. Two full meals in an 8-hour window covers what you need.
- Pick your eating window around your life, not around theory: people who train in the evening usually skip breakfast; people who eat dinner with family move dinner earlier.
- You don't have to fast every day: 4-5 days a week already gets results and is far easier to keep up.
- OMAD, 20/4 and 24 to 72 hour fasts are occasional tools, not a starting point.
Reading path
The articles on this topic in the order that makes sense. Each one answers a specific question.
16/8 intermittent fasting means eating within an 8-hour window and fasting the other 16, sleep included. To start, ease in gradually (12/12, then 14/10, then 16/8) and stick to water, black coffee or unsweetened tea during the fast. In 8-12 week studies it produces modest weight loss (2-3%) with no calorie counting.
Read · 8 min →12/12 fasting means fitting all your meals into 12 hours and fasting the other 12, sleep included. It's the gentlest entry point to intermittent fasting: just move dinner earlier or breakfast later. Observational data link an overnight fast of at least 13 hours with better blood sugar control and more hours of sleep.
Read · 5 min →When 16/8 isn't enough: 20/4 fasting (the warrior diet) and one meal a day (OMAD). Benefits, risks, and how to try them.
Read · 6 min →You eat normally 5 days and cut calories hard on 2. An alternative to 16/8 for people who would rather not fast every day.
Read · 6 min →Water fasting means consuming nothing but water for 24-72 hours or more. In trials running 5-20 days it produces weight losses of 2-10%, higher ketones, and lower blood pressure, but close to two thirds of the weight lost is lean mass and the metabolic benefits fade within 3-4 months. Long fasts are best done under medical supervision.
Read · 7 min →The two most common ways to run 16/8. How to choose based on your life, your energy and your results.
Read · 5 min →A daily 16-hour fast (16/8) is sustainable for most healthy adults and is the most studied approach. Fasts of 24 hours aren't a good idea daily: alternate-day fasting trials show results similar to calorie restriction, higher dropout, and, in lean people, less fat loss. Long fasts are best saved for once or twice a week.
Read · 5 min →Work, commutes, coffee runs, dinners out… city life fights your fast. Here is a realistic method to fast without fighting your calendar.
Read · 6 min →Hunger is the #1 reason people quit. These tricks make riding out your fasting window genuinely easy.
Read · 5 min →What the science says
- 16/8 for 12 weeks in adults with obesity: -2.6% body weight, -341 kcal/day and -7 mmHg systolic pressure, with no calorie counting (Gabel 2018). [1]
- Among 2,413 women with breast cancer, fasting less than 13 h overnight was associated with a 36% higher risk of recurrence (HR 1.36) (Marinac 2016). [2]
- Fasts of 5-20 days: weight loss of 2-10%, roughly two thirds of it lean mass; metabolic benefits were not maintained at 3-4 months (Ezpeleta 2024). [3]
- Alternate-day fasting for 1 year: -6.0% body weight versus -5.3% with daily calorie restriction (not significant); 38% dropout (Trepanowski 2017). [4]
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Frequently asked questions
What's the best intermittent fasting protocol for beginners?
How long does it take to adjust?
Can I do intermittent fasting if I take medication or have a health condition?
What do I do if I can't stick to my window one day?
Sources cited on this page (4)
- Effects of 8-hour time restricted feeding on body weight and metabolic disease risk factors in obese adults: A pilot study. Nutrition and Healthy Aging, 2018.
- Prolonged Nightly Fasting and Breast Cancer Prognosis. JAMA Oncology, 2016.
- Efficacy and safety of prolonged water fasting: a narrative review of human trials. Nutrition Reviews, 2024.
- Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults. JAMA Internal Medicine, 2017.