What is intermittent fasting?
Intermittent fasting (IF for short) is an eating pattern that focuses on when you eat rather than what you eat. The day is divided into two windows: an eating window and a fasting window. During the fasting window, water, unsweetened tea and coffee are allowed; nothing containing calories is taken. During the eating window you eat your daily meals normally. The most common version is 16:8: 16 hours of fasting and an 8-hour eating window. For example, you eat between 12.00 and 20.00 and do not eat from 20.00 until 12.00 the next day; most of that time is spent asleep anyway.
Intermittent fasting is not a new invention; the human body has adapted to long gaps between meals over millions of years. What is new is using it as a planned weight-management tool.
How does it work?
For a few hours after a meal, the body primarily uses the energy from that meal and insulin stays high. When the gap between meals grows, insulin falls, the body uses up stored glycogen and then turns to its fat stores. A 16-hour fasting window gives this transition time to happen. In addition, because the eating window is narrow, total daily calories tend to fall by themselves; night-time snacking, late desserts and irregular snacks disappear. This is the real engine of weight loss: the total calories that decrease once eating times become regular.
One important warning: eating whatever you want, as much as you want, in the eating window cancels out the effect of the fast. Intermittent fasting works when it sits on top of balanced eating.
Common methods
- 16:8 — 16 hours fasting, 8 hours eating. The easiest and most recommended method; having a late breakfast and finishing dinner early is enough for most people.
- 14:10 — A gentler version for beginners; suitable especially for women and first-timers.
- 5:2 — Normal eating on 5 days of the week, very low calories on 2 days. Harder to follow and requires a dietitian's supervision.
On Diet Prof, 16:8 and 14:10 are used mainly; your meal times are set according to the window you choose.
A sample 16:8 day
- 08.00: Water, unsweetened tea or plain coffee. The fast continues.
- 12.00 – first meal: A two-egg vegetable omelette or a cheese omelette, plenty of greens, 1 slice of wholemeal bread.
- 15.30 – snack: 1 bowl of yoghurt with a handful of strawberries, or 1 apple and 5 walnuts.
- 19.00 – dinner: Grilled meatballs or baked salmon, vegetables in olive oil, 3 tablespoons of bulgur pilaf, salad.
- After 20.00: Only water and herbal tea. The window is closed.
Benefits
- Reduces total calories without counting them; ends night-time snacking.
- Planning and preparation become easier because there are fewer meals.
- Blood sugar fluctuations decrease; many users report more even energy during the day.
- It breaks the fear of going hungry: you experience that the body works perfectly well for a few hours without food.
Points to watch and who should not do it
Intermittent fasting is not for everyone. It should not be followed, or only with a doctor's approval, during pregnancy and breastfeeding, under the age of 18, by people taking diabetes medication or insulin, by anyone with a history of eating disorders, and by people with low blood pressure. Hunger and headaches can occur in the first days; drinking plenty of water and narrowing the window gradually (first 12:12, then 14:10, then 16:8) eases the transition. Putting protein and vegetables first in the eating window carries fullness into the next day.
The 5 most common mistakes
- Eating freely in the eating window. Excess calories taken in 8 hours wipe out the effect of 16 hours of fasting.
- Jumping to 16 hours in one day. A gradual transition (12:12, 14:10, 16:8) prevents headaches and fatigue.
- Drinking too little water while fasting. What feels like hunger is often thirst.
- Making the first meal light. The first meal of the window should contain protein and vegetables; otherwise hunger grows all day.
- Doing it when it is not suitable. With pregnancy, breastfeeding, diabetes medication or low blood pressure, a doctor's approval is essential.
How is intermittent fasting applied on Diet Prof?
After the free analysis, you state that you prefer intermittent fasting as your diet type, or send it from Dietitian Support in your profile. Your meal times are set according to your eating window; for example, in a 12.00–20.00 window, three meals as first meal, snack and dinner. Your daily calorie target is distributed across these three meals; the recipe, quantities and calories of every meal are on your list. Meal Reminder sends notifications to your phone at the opening and closing times of the window; you can shift the window whenever you like from Diet Settings. You see your weekly progress in the Change Graphs. For details, see the How Does Diet Prof Work? page.
Frequently asked questions
Can I drink coffee during fasting hours?
Yes; plain coffee and tea without sugar, milk or cream do not break the fast.
Isn't skipping breakfast harmful?
In intermittent fasting breakfast is not skipped, it is postponed. The first meal is eaten at 12.00 and is one of the most balanced meals of the day.
If I exercise, when should I train?
Light workouts can be done in the fasting window; strength training gives better results inside the eating window, ideally after the first meal. The dietitian team arranges your meals around your training time.
Start now
Intermittent fasting is a simple and powerful routine for people tired of counting calories. See your daily need with the free analysis, choose your window and let your list be ready.
