There are several different interpretations of the circadian diet, but most typically involve eating within a set ‘window’ and fasting overnight. This usually involves a 12 hours on/12 hours off approach. That might mean, for example, eating between 7am and 7pm and then fasting until the morning.

“Some research also suggests that the ideal eating hours for a circadian rhythm fast might be between 8am-6pm,” explains Hannah Alderson, a BANT-registered nutritionist and hormone specialist. “This is a kind of early time-restricted eating pattern, where you break your fast in the morning and enter into another fast later in the afternoon.”

This varies from most forms of intermittent fasting because it involves eating first thing when you wake up in the morning, as opposed to holding off until later in the day. This is because fluctuations in your circadian rhythm lead to an increase in insulin sensitivity in the morning, which allows the cells of the body to use glucose more effectively, keeping blood sugar stable.

Should we let our body clock dictate how and when we eat? The circadian diet, explained