What is intermittent fasting?
Intermittent fasting (IF) is an eating pattern that cycles between periods of eating and periods of fasting. Rather than changing what you eat, it changes when you eat. The most popular method, 16:8, means fasting for 16 hours (including sleep) and eating all your meals within an 8-hour window — for example from 12 noon to 8 pm.
For many families in the Gulf and South Asia, fasting is also a familiar part of life through Ramadan. This intermittent fasting calculator helps you plan everyday IF schedules and a balanced Ramadan routine.
How the fasting calculator works
You choose a method and the time of your first meal. The calculator adds the length of your eating window to find when it closes, and shows your fasting period until your next first meal:
- Eating window ends = first meal time + eating hours
- Fasting period = 24 hours − eating hours
Example: on 16:8 with a first meal at 12:00 pm, your eating window is 12:00 pm – 8:00 pm and you fast from 8:00 pm until noon the next day.
In Ramadan mode, enter your local Fajr and Maghrib times. The calculator shows your fasting hours and suggests a simple iftar, dinner, snack and suhoor timeline plus a water plan.
Intermittent fasting methods: low, moderate and high intensity
| Method | Fasting / eating | Level | Best for |
|---|---|---|---|
| 12:12 | 12 h / 12 h | Gentle | Beginners; simply stop late-night snacking |
| 14:10 | 14 h / 10 h | Moderate | Women, beginners, people with busy family schedules |
| 16:8 | 16 h / 8 h | Moderate | Most healthy adults wanting weight or blood sugar benefits |
| 18:6 | 18 h / 6 h | Strict | Experienced fasters |
| 20:4 and OMAD | 20–23 h / 1–4 h | Very strict | Not recommended for most; hard to meet nutrient needs |
Potential benefits of intermittent fasting
- Weight loss: a shorter eating window often means fewer calories, with results similar to regular calorie counting.
- Better insulin sensitivity and blood sugar control in some people with prediabetes or insulin resistance.
- Less late-night snacking and better sleep when you stop eating 2–3 hours before bed.
- Simplicity: fewer meals to plan and no special foods required.
- Possible gut benefits from an overnight rest — read can intermittent fasting improve gut health?
Health warnings — who should not fast without medical advice
- People with type 1 diabetes, or type 2 diabetes on insulin or sulfonylureas (risk of dangerous low blood sugar).
- Pregnant or breastfeeding women, children and teenagers.
- Anyone with a history of eating disorders.
- People who are underweight, frail or older adults with low appetite.
- People with kidney disease, low blood pressure, or taking medicines that must be taken with food.
- Stop and seek help if you feel faint, confused, have palpitations or severe headaches while fasting.
Tips for healthy fasting
Break your fast with protein and fibre rather than sweets; include vegetables, wholegrains and healthy fats; drink plenty of water during your eating window (use the water intake calculator); and keep total calories in check with the calorie calculator. During Ramadan, our healthy suhoor and iftar guide has meal ideas, and people with diabetes should read managing type 2 diabetes through nutrition.
Frequently asked questions
What is the best intermittent fasting schedule for beginners?
Start with 12:12 or 14:10 for one to two weeks, then move to 16:8 if you feel well. Many people find an eating window from about 10 am to 6 pm or 12 pm to 8 pm easiest.
Can I drink water, tea or coffee while fasting?
During intermittent fasting, water, black coffee and plain tea without sugar or milk are fine and will not break your fast. During Ramadan, nothing is consumed between Fajr and Maghrib.
Is 16:8 intermittent fasting good for weight loss?
It can be, mainly because it helps many people eat fewer calories. Studies show weight loss similar to standard calorie-controlled diets, so choose the approach you can keep up.
Is intermittent fasting safe for women?
Many women do well with gentle methods such as 14:10 or 16:8. Women who are pregnant, breastfeeding, trying to conceive, or have irregular periods or a history of eating disorders should get advice first.
How can I avoid feeling thirsty during Ramadan?
Drink water steadily between iftar and suhoor, eat water-rich foods like cucumber, watermelon and yoghurt, and limit salty, fried and very sweet foods and strong tea or coffee at suhoor.
Sources
- de Cabo R, Mattson MP. Effects of intermittent fasting on health, aging, and disease. N Engl J Med 2019;381:2541–2551.
- Lowe DA, et al. Effects of time-restricted eating on weight loss (TREAT trial). JAMA Intern Med 2020.
- International Diabetes Federation & DAR International Alliance. Diabetes and Ramadan: Practical Guidelines. 2021.