Which eating window fits your day? Set your first meal and see

"Eat between 12 and 8" sounds simple until your day has a morning workout, a school run and dinner with friends in it. The useful question for a beginner is not "which fasting plan is best?" but "which eating window could I actually keep to?" Here is how to find out, and what the research says about whether it matters.

What an eating window is

An eating window is the stretch of the day when you eat, with a longer break the rest of the time. In "16:8" you eat within 8 hours and go 16 without food; "14:10" and "12:12" work the same way. Water is fine in the break, and our coffee guide covers what counts. The break includes your sleep, which is why a 12:12 window is not far from what many people already do: dinner at 19:00, breakfast at 07:00.

The best eating window is the one that fits your life, because the research does not show that a shorter one works better.

Does a shorter window help?

The evidence says: not reliably. In a 12-month trial of 139 adults with obesity, everyone followed the same calorie targets, and half also ate only between 08:00 and 16:00. The window group lost 8.0 kg and the others 6.3 kg, a gap of 1.8 kg that was not statistically significant, so the window added no clear benefit. A Cochrane review of 22 randomised trials with about 2,000 adults who were overweight or obese found that intermittent fasting led to similar weight loss to ordinary dietary advice. These trials were fairly short, and the review notes few large, high-quality studies, so long-term effects are still unknown.

Some small studies hint at other benefits. In a small five-week study of men with prediabetes, eating all meals early in the day improved insulin sensitivity and blood pressure even though weight stayed stable. It was a small, short study, so treat it as a question for bigger trials rather than an answer.

How to choose a window

Start with the longest window you can imagine keeping, often 12 or 14 hours, and try it for a couple of weeks before changing anything. Keep your usual food and amounts; the aim is to fit your normal meals into the window, not to eat less. Put the window where your life already has meals, such as family dinners, and make sure each meal has some protein and fibre. If you are always hungry, tired or irritable, that is useful information. Widen the window or drop the idea.

You do not need a window at all to eat well. For many people, regular meals and sensible portions do the job.

Who should not do this

This guide is general information, not medical advice. Please talk to a doctor or dietitian before limiting when you eat if you have a medical condition, particularly diabetes, or take medication, especially for diabetes or blood pressure, which may need adjusting. Skip it if you are pregnant or breastfeeding, or have or have had an eating disorder, and see a professional if rules about when to eat start to feel stressful. NHS and British Dietetic Association guidance is clear that people in these groups should not delay or skip meals.

Sources

• Liu et al., Calorie Restriction with or without Time-Restricted Eating in Weight Loss, NEJM 2022
• Cochrane review: intermittent fasting for weight loss (CD015610)
• Sutton et al., Early time-restricted feeding improves insulin sensitivity, blood pressure and oxidative stress, Cell Metabolism 2018
• NHS My Health London: Intermittent fasting (with British Dietetic Association advice)