Intermittent fasting for weight loss: how it works, benefits, and risks

What is intermittent fasting?

‍Intermittent fasting is about when you eat, not what you eat. You alternate between periods of eating and fasting. Whatever the set-up, the aim is usually to reduce your overall calorie intake, which can then lead to weight loss.

Common types of intermittent fasting

16:8 – 16 hours fasting

‍With the 16:8 approach, you fast for 16 hours and eat your meals within an 8-hour window, for example between 11:00 and 19:00. Many people find this reduces grazing and helps meals feel more settled day to day.

5:2 – two lower-intake days

‍With 5:2, you eat as usual five days a week and cut your energy intake significantly on two non-consecutive days. This set-up often needs a bit more planning, but it can work well if you like clear structure and “low days”.

Eat-Stop-Eat – 24-hour fasts

‍Once or twice a week, you fast for 24 hours, for example from dinner to dinner. This can feel more challenging and won’t suit everyone.

How can intermittent fasting support weight loss?

Lower energy intake

‍By eating within a limited time window, many people naturally reduce how much they eat overall, simply because there are fewer opportunities to eat.

More structure in daily life

‍Intermittent fasting can create clear boundaries for meals and reduce spontaneous eating, especially in the evenings.

More awareness of eating habits

‍A shorter eating window can make you more mindful of what you choose, which may lead to more nourishing options and less snacking.

Possible benefits of intermittent fasting for reaching a healthy weight

• Simple structure: few rules, clear set-up.
• Flexibility: can be adapted to your routine, training, and sleep.
• Less evening eating: for many people, a defined eating window means fewer chances for unplanned snacking or high-calorie foods late at night, which can reduce overall intake.
• May suit people who dislike frequent small meals: some people feel better eating less often but having larger meals, and fasting can feel more natural than lots of small meals.
• Works alongside other healthy habits: like a balanced, nourishing diet, regular movement, and, when needed, medical treatment. These are the building blocks most strongly linked to long-term weight regulation in research.

Risks and limitations to be aware of

Intermittent fasting isn’t usually harmful for people who are generally healthy and find it works for them. But some groups should avoid it, including people who are pregnant, breastfeeding, living with diabetes treated with insulin, or who have (or have had) an eating disorder.

Some people notice tiredness, headaches, or lower energy during fasting periods. For others, fasting can feel socially limiting.

It’s also worth knowing that many people tend to make more nutritious choices earlier in the day than in the evening. So for some, keeping breakfast and focusing on reducing evening eating can be more helpful for weight loss, and feel more sustainable.

Whenever intake goes down, no matter the method, there’s a risk you may not get enough protein, fibre, healthy fats, vitamins, and minerals. Fluid intake can be affected too, because some of the fluid we take in each day comes from the food we eat.

Want to lose weight: intermittent fasting or not?

The most important thing is to listen to your body. Intermittent fasting can be helpful for some people, but it’s not a must for weight loss.

If you choose to try intermittent fasting, it can help to:

• eat a varied, nourishing diet
• avoid “making up for it” by overeating when you do eat
• drink water regularly
• adjust exercise to match your energy levels
• pay attention to your body’s signals

At Yazen, we know sustainable weight loss is built from several parts: food habits that work for you, support with behaviour change, movement, sleep, and, when needed, medical treatment. Intermittent fasting can be a useful add-on for some, but the key is finding an eating pattern that feels doable long term and fits your life.

Combining intermittent fasting with physical activity

For the best results in weight loss, whatever approach you choose, it helps to pair diet changes with regular physical activity. Movement doesn’t just increase calorie burn, it supports health in lots of ways: strengthening your heart, maintaining muscle, and improving mood.

Try to match your training to how you feel during fasting periods, and choose activities that suit you, whether that’s walking, strength training, or cardio. Regular movement can also boost motivation and make it easier to stick with both fasting and healthier eating habits over time.

Summary

Whatever method you use, a calorie deficit is what ultimately drives weight loss. Intermittent fasting can help some people reduce energy intake, but it doesn’t guarantee a deficit on its own, whether you use eating windows or fasting days.

Research suggests it’s not especially important how the calorie deficit is created for weight loss: fewer meals, shorter eating windows, lower-calorie days, or a steadier daily deficit can all work. What matters most is finding an eating pattern that supports your goals and that you can stick with long term. That long-term consistency is what makes weight loss more sustainable and helps you reach or maintain a healthy weight.