Improving the evidence on the effects of intermittent fasting on appetite

This project explored ways to monitor the effects of intermittent fasting on appetite and eating behaviour. Intermittent fasting is when a person alternates between fasting and eating normally.  

What we did

We reviewed data from 17 clinical trials comparing intermittent fasting and standard dieting. This allowed us to explore the potential effects of both on appetite. 

We found no clear evidence to suggest that intermittent fasting had a different effect to standard dieting. This finding is different from other reviews of the evidence, which have suggested that intermittent fasting may be beneficial in reducing the drive to eat that can accompany weight loss. 

However, many of the studies we looked at only measured appetite once a day, which was often before breakfast. They didn’t explore how these diets affect changes in appetite throughout the day. 

To get a full picture of how people’s appetite changes over the course of a day, we designed and developed Momentary Appetite Capture (MAC). MAC is an ‘ecological momentary assessment’ (EMA) tool.  

EMA is about understanding how someone feels at different moments throughout the day. It is a research method that collects real-time data from individuals in their natural environment, for example through an app. It captures behaviours, thoughts, and experiences as they occur, rather than relying on reports afterwards. 

Our MAC tool aimed to track appetite and portion-size throughout the day. As part of this project, the tool was used in several studies.  

What we found

We found that MAC: 

• Gave consistent results 

• Was acceptable to participants 

• Captured individual differences in appetite and eating behaviours 

One of the studies showed that one day of intermittent fasting didn’t change people’s beliefs about appetite. 

We also used MAC in two clinical trials working with Oxford Medical Products. In these trials, we explored how Sirona, a novel weight loss technology, impacted appetite beyond the immediate dosing period and in participants’ everyday lives. 

Together, findings from this project suggest that MAC is a useful tool to investigate daily appetite patterns.  

What next?

We will use MAC to explore how changes in daily appetite relate to changes in body weight and energy intake over time.  

MAC could be used to better understand the mechanisms of weight-loss interventions, as well as to explore dietary behaviour and energy balance more broadly. 

This research is part of a PhD project being carried out by Becca Elsworth with supervision provided by Dr Ella Hinton, Professor Jeff Brunstrom and Professor Julian Hamilton-Shield.