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Updated 25th November 2022

The Big IF Study: What have we found so far?

Written byYella Hewings-Martin, PhD
Reviewed byKate Bermingham, PhD

    Download the free app now to try intermittent fasting with the 100,000 people who have already joined the study.

    Over 100,000 of you have already joined The Big IF Study. And over 10,000 have also joined our new Facebook community, where members are discussing all the highs and lows of doing intermittent fasting.  

    Together, we’re now running the largest intermittent fasting study in the world. 

    At ZOE, our mission is to understand and improve health for everyone, whether that’s through the ZOE Health Study or our work on nutrition and the microbiome.

    With The Big IF study, we want to find out how when you eat impacts factors like your hunger, mood, and energy, as well as your overall health. 

    Our first group of Contributors are coming to the end of their 3 weeks in the study. But for tens of thousands of them, their intermittent fasting journey is far from over. 

    We want as many of you as possible to continue with the experiment to help gather important data so we can understand the benefits of intermittent fasting. 

    "It may take longer than 2 weeks for some people before they see any effects when they first start intermittent fasting,” says Dr. Sarah Berry, chief scientist at ZOE.  

    “Tens of thousands of contributors have already opted to extend their time in the study. This will help us get a better understanding of the longer term effects of intermittent fasting and allow our Contributors to see what happens when they stick with it," Sarah explains. 

    Why not join them?

    What has The Big IF Study revealed so far?

    There are over 100,000 Contributors taking part in the study, including people of all ages ranging from 18 to 96. 

    The average age is 60, and nearly 77% of our study Contributors are female.

    We’ve looked at how many times a day our study participants eat. We call these “eating events,” and they include meals and snacks. 

    Looking at the data from the baseline lifestyle survey — which our Contributors fill in before they start intermittent fasting and which captures information on their typical diet and lifestyle patterns — we’ve seen that people with a longer habitual eating window tend to eat more times each day than those with a shorter eating window. 

    Most of our study participants reported eating two snacks per day, typically. But those who snack more frequently eat more on their days off than on their working days. 

    The average eating window is 11.4 hours, and the most common time that our Contributors eat their last meal of the day is at 8:30 p.m. The most common time they eat in the morning is at 8 a.m.

    Once they’ve started intermittent fasting, some of our contributors have noticed increased energy, better digestion, less bloating, weight loss, and reduced snacking and hunger. 

    As we continue to look at the data from The Big IF Study, we want to find out if significant numbers of our Contributors experience such improvements and whether these are linked with changes to their usual diet and lifestyle habits.

    What are the top reasons for taking part?

    There are many different reasons why our Contributors are taking part in The Big IF Study. 

    One common theme we keep hearing is that you want to contribute to science. 

    Being part of the largest community science study into intermittent fasting gives you that opportunity. But there are also other reasons. 

    These include looking for better ways to manage your hunger and blood sugar levels, seeking support through menopause and the weight gain that many people experience during this time, and finding an alternative to calorie counting. 

    Some of you have tried intermittent fasting before and are keen to get back into it with this study. Others are looking to see if this way of eating can support their general health and help prevent disease in the long term. 

    As a Contributor, you can also be part of our Facebook community and share your experiences and tips with others who are taking part in The Big IF Study. 

    Why do we want Contributors to extend?

    Changing your eating habits can take time. We’ve seen that many of you are adjusting your eating window to 10 hours during the intermittent fasting part of the study. 

    And some of you are already seeing changes to your hunger, mood, and energy levels, as well as to the daily symptoms that you normally experience. 

    But 2 weeks is just the beginning. It can take a little longer for some people to see any changes, especially if this is their first foray into changing when they eat. 

    To gather enough data for our scientists to see the longer-term effects of intermittent fasting, we’re inviting all of our Contributors to continue the study and keep logging. 

    How does it work?

    As part of The Big IF Study, our Contributors spend the first week eating their normal meals and snacks. Meanwhile, they log how they feel each day and when they ate their first and last meal. 

    During the following 2 weeks, our amazing Contributors then move on to the intermittent fasting part of the study, with the aim to eat all their regular meals and snacks during a 10-hour window. They change when they eat, but not what they eat. 

    They also keep logging their hunger and energy levels, mood, and usual health symptoms.  

    It’s OK to change the timing of the 10-hour eating window, starting early and finishing early some days, and starting later and finishing later on others.  

    We also understand that some days, people don’t stick to this schedule. 

    But we know that reducing the eating window is good for health, even if someone doesn’t reach a 10-hour window. Changing from a 12-hour eating window to an 11-hour eating window is a great step in the right direction. 

    All of the data that our Contributors provide is valuable, whether they manage to stick with intermittent fasting or not. Together, it helps us to study how feasible intermittent fasting is and what the effects are of changing when we eat. 

    We also want to know what people like or dislike about this way of eating and if it could be a sustainable lifestyle change in the longer term. 

    It’s not too late to get involved. You can join The Big IF Study anytime