Intermittent fasting (IF) has become one of the most talked-about approaches to weight loss. Instead of focusing on what you eat, it focuses on when you eat. For some people it makes eating less feel simpler; for others it is a poor fit. Here is what you need to know before trying it.
What intermittent fasting is
Intermittent fasting means cycling between periods of eating and periods of not eating (or eating very little). It is a pattern rather than a specific diet, so you still choose what foods to eat during your eating window.
Common approaches
- Time-restricted eating (such as 16:8): You eat within a set window each day, for example from noon to 8 p.m., and fast for the remaining hours. Variations include 14:10 or 12:12, which are gentler starting points.
- 5:2: You eat normally five days a week and significantly reduce calories on two non-consecutive days.
- Alternate-day fasting: You alternate between normal eating days and very low-calorie days. This is more demanding and not usually where beginners start.
- Occasional 24-hour fasts: Some people fast for a full day once or twice a week. This can be difficult and is not necessary for weight loss.
How it can help with weight loss
The main way intermittent fasting helps with weight loss is simple: a shorter eating window often means fewer meals and snacks, which can lead to eating fewer calories overall. Many people also find that having clear rules ("I do not eat after 8 p.m.") reduces mindless snacking.
Research comparing intermittent fasting with standard daily calorie reduction has generally found similar weight loss when total calories are similar. In other words, IF is a tool for creating a calorie deficit, not a magic shortcut. If you eat more than you burn during your eating window, you will not lose weight. Our guide to how many calories to eat to lose weight still applies.
Potential benefits beyond calories
Some people like intermittent fasting because:
- It can simplify planning, since there are fewer meals to think about.
- It can reduce late-night eating.
- Some people find they feel less hungry once they adjust.
Research into other potential health effects is ongoing, and results vary. It is wise to be skeptical of dramatic claims you see online.
Potential downsides
- Hunger and irritability, especially in the first couple of weeks.
- Overeating during the eating window, which can cancel out the deficit.
- Difficulty with social meals, family dinners, or work schedules.
- Lower energy for workouts if training falls during a fast.
- Not suitable for everyone, as explained below.
Who should avoid it or get medical advice first
Intermittent fasting is not appropriate for everyone. Talk with a healthcare professional before trying it if you:
- Are pregnant, trying to become pregnant, or breastfeeding
- Have diabetes or take medications that lower blood sugar, such as insulin
- Have a history of eating disorders or disordered eating
- Are under 18 or are an older adult with health concerns
- Have low blood pressure, are underweight, or have other medical conditions
Tips if you want to try it
- Start gently. Try a 12-hour overnight fast, such as 7 p.m. to 7 a.m., then extend gradually if it feels good.
- Stay hydrated. Water, plain tea, and black coffee are usually fine during fasting periods for most people.
- Eat balanced meals. Include protein, vegetables, fruits, whole grains, and healthy fats. See Protein for Fat Loss.
- Do not use the window as a free-for-all. Keep your calorie target in mind. Use our calculator to find it.
- Be flexible. Shift your window for social events or skip fasting on days when it does not fit.
- Pay attention to how you feel. Dizziness, weakness, or obsessive thoughts about food are signs to stop and reconsider.
Intermittent fasting versus regular meal patterns
There is no single best meal pattern for everyone. Some people do well with three meals a day, others with two, and others with several small meals. The best approach is the one that helps you stay within your calorie target, get good nutrition, and feel well. If intermittent fasting makes that easier, it can be a useful tool. If it makes you miserable, you can lose weight perfectly well without it.
The bottom line
Intermittent fasting is a way of organizing when you eat. It can help some people eat less, but it works mainly through calorie reduction, like any other diet. Start gently, keep meals balanced, respect your calorie target, and skip it if it does not suit your health or lifestyle. Find your personal target with our free weight loss goal calculator.
This article is for general information only and is not medical advice. Talk with a qualified healthcare professional about your individual needs. Last updated November 1, 2026.