The simplest way to start intermittent fasting is to close your kitchen after dinner and delay breakfast the next morning, giving yourself a 12-hour overnight fast. From there, you gradually widen that fasting window over a few days or weeks until you reach a schedule that fits your life. Most beginners land on a 16:8 pattern, where you eat during an 8-hour window and fast for 16 hours, but several other approaches work just as well.
Choose a Fasting Schedule
There’s no single “right” way to do intermittent fasting. The best schedule is the one you can actually stick with. Here are the most common options:
- 16:8 method: Eat only during an 8-hour window, such as 11 a.m. to 7 p.m., and fast for the remaining 16 hours. A gentler version, 14:10, uses a 10-hour eating window (for example, 9 a.m. to 7 p.m.). This is the most popular starting point.
- 5:2 method: Eat normally five days a week and cap your intake at about 500 calories on two non-consecutive days. You pick the fasting days, as long as there’s at least one regular eating day between them.
- Alternate-day fasting: Every other day, limit yourself to roughly 500 calories (about 25% of what you’d normally eat). A large network analysis of clinical trials found this approach produced the most weight loss of any fasting strategy, averaging about 3.4 kilograms (roughly 7.5 pounds) more than eating without any structure.
- 24-hour fasts (Eat Stop Eat): Fast completely for a full 24 hours, typically once or twice a week. This is the most demanding option and not ideal for beginners.
Time-restricted eating methods like 16:8 produced more modest weight loss in trials, averaging about 1.7 kilograms compared with unrestricted eating. But they also tend to be the easiest to maintain, which matters more over months than any short-term number on a scale.
Ease In Over One to Two Weeks
Jumping straight into a 16-hour fast often backfires. A better approach: start with a 12-hour fasting window. If you finish dinner at 7 p.m., that just means waiting until 7 a.m. to eat. Most of the fast happens while you sleep, so it barely feels like a change.
Once 12 hours feels easy, push your first meal back by 30 to 60 minutes every few days. Within a week or two, you can comfortably reach 14 or 16 hours without the headaches and irritability that come from doing too much too fast. This gradual ramp also gives your hunger hormones time to adjust, so the fasting window stops feeling like white-knuckling it.
What You Can Drink While Fasting
Water, black coffee, and plain tea are all fine during a fast. They contain essentially no calories and won’t trigger a meaningful insulin response. If you need something more substantial during a longer fast, bone broth can help replenish electrolytes, though it does technically contain calories and will break a strict fast. Small amounts of milk or fat in your coffee fall into a gray area: they’ll add a few calories, but some people find that trade-off worthwhile because it helps them stay consistent.
Anything with sugar, juice, cream, or protein powder will break your fast. If you’re unsure, the simple rule is: if it has calories, it counts as eating.
What Happens in Your Body
During the first several hours of a fast, your body burns through its stored sugar (glycogen) for energy. Once those reserves run low, typically somewhere around 12 hours, your metabolism shifts toward burning fat for fuel. This transition is one reason people experience weight loss with fasting, beyond simply eating fewer total calories.
All fasting strategies in clinical trials showed small improvements in fasting blood sugar and insulin sensitivity compared with unrestricted eating. Alternate-day fasting also lowered triglycerides, blood pressure, and cholesterol levels more than time-restricted eating did. These metabolic changes tend to build over weeks of consistent practice, not from a single skipped breakfast.
You may have heard about autophagy, a cellular cleanup process where the body breaks down and recycles damaged components. Animal studies suggest autophagy ramps up somewhere between 24 and 48 hours of fasting, but there isn’t enough human research to pin down an exact timeline. For most people doing daily 16:8 fasts, the primary benefits come from improved insulin sensitivity and reduced calorie intake rather than autophagy.
Common Side Effects and How to Handle Them
The first week is the hardest. Headaches, low energy, irritability, and constipation are all common as your body adjusts. Most of these symptoms fade within 7 to 10 days. Staying well hydrated helps significantly, since thirst can masquerade as hunger and contribute to headaches.
Electrolyte imbalances can also play a role, especially if you’re fasting for longer stretches or take blood pressure or heart medications. Adding a pinch of salt to your water or drinking mineral water can help with sodium levels. If you feel dizzy, unusually weak, or notice muscle cramps, those are signs your electrolytes need attention.
Hunger itself usually comes in waves rather than building steadily. If you can ride out a 15- to 20-minute surge, it typically passes. Keeping busy during the last hour or two of your fast makes a noticeable difference, especially in the beginning.
How to Break Your Fast
What you eat first matters more than most beginners expect. Diving into a large, heavy meal after hours of fasting often leads to bloating, gas, and stomach pain. Foods high in fiber, fat, or sugar are the worst offenders when your digestive system has been idle.
Instead, start with something small and easy to digest:
- Eggs, scrambled or soft-boiled
- A smoothie with fruit and protein
- Yogurt or kefir
- Broth-based soup with lentils or tofu
- Soft, cooked vegetables
- Avocado
Give yourself 20 to 30 minutes after this smaller meal before eating a full plate. Your body needs time to restart digestive enzymes and signal fullness. This two-stage approach also helps prevent the overeating that can cancel out the calorie reduction fasting provides.
Who Should Be Cautious
Intermittent fasting isn’t appropriate for everyone. It’s not recommended for anyone under 18, people who are pregnant or breastfeeding, or anyone with a history of disordered eating. Restricting eating windows can reinforce unhealthy patterns around food for people recovering from conditions like anorexia or binge eating.
Athletes and highly active people may struggle to get enough fuel within a shortened eating window, which can hurt performance and recovery. If you have diabetes or take medications that affect blood sugar, fasting can change how those medications work in ways that need medical oversight. The same applies to people on blood pressure or heart medications, since longer fasts can shift electrolyte balance enough to matter.
Making It Stick Long Term
Consistency matters more than perfection. Fasting most days of the week produces better results than doing it sporadically, but missing a day here and there won’t erase your progress. Many people find weekdays easier because routine makes the schedule automatic, then eat more flexibly on weekends.
Pair your fasting schedule with nutrient-dense meals during your eating window. Fasting doesn’t give you a free pass to eat anything. The calorie reduction only works if you’re not compensating by eating significantly more during your feeding hours. Focus on protein, vegetables, healthy fats, and whole grains to stay full longer and get the micronutrients your body needs from fewer meals.
Track your energy levels and hunger patterns for the first two to three weeks. If a particular schedule leaves you unable to concentrate at work or ruins your sleep, adjust the window rather than forcing through it. Moving your eating window an hour earlier or later, or switching from 16:8 to 14:10, can make the difference between a habit that lasts and one you abandon after a month.