Keto and intermittent fasting (IF) are tied for the number one hottest diet of 2018 and 2019. I've heard many people say IF isn't a diet because they can eat whatever they want and still 'be healthy.' Many have said that they like how it makes things simple with when and when not to eat and that is really the only 'rule' that has to be followed. Clinically, I've worked with several clients who are still intermittently fasting and have had a lot of success with it. Full disclosure, I did not recommend they start.
What is it?
There are an incredible number of varieties of intermittent fasting out there. Eating in an 8 hour window and fasting for 16. Fasting for two days of the week, eating less than 500 calories during those days and then eating normal the other days of the week. Fasting for 23 hours of the day and eating your typical calories in a one hour span. Eating for 4 hours and fasting for 20. You get the picture. Any variation of this way of eating you want to find, you basically can. Broken down very simply (with a strong non-diet dietitian lens) intermittent fasting is ignoring your body's hunger and fullness cues based on when a clock says that you can and cannot eat.
Not surprisingly, most of the research on intermittent fasting has focused on it as a method for weight loss. As with most research focused on weight loss (which is often heavily fat-phobic), it was successful for short term weight loss. Short term weight loss is usually a period of 6 months. In other words, specific to weight loss, it was ineffective for anything other than short term. If you are considering starting intermittent fasting to support weight loss, it appears to be as effective as every other diet to date. For long term weight loss, this effectiveness is somewhere around less than 5 percent of the population being able to lose weight and "keep it off" for greater than 6 months to 2 years. Intermittent fasting isn't any different when it comes to shrinking your body than any other diet and will most likely not be successful in the long term.
However there is also some research examining if fasting can support brain health, immune function and potentially reduce the risk of certain diseases. This research appears promising and has only been done on animals extensively. Humans are mammals but we are definitely not animals. We have different needs, we have incredible brains that respond differently and we have many different stressors. Currently, clinical research studies focused on intermittent fasting that are well designed and have good evidence, are incredibly sparse. There are a few that may show improvement in diabetes risk markers and heart disease risk markers AND YET I'm still not recommending it as a way to support your health. The research isn't there yet and I know there are other ways to support your diabetes risk markers and heart health that involve eating regularly throughout the day, every day.
What I am recommending
I mentioned above that intermittent fasting is essentially ignoring your body's demands for food until an external source says that it is okay to eat. In this case, that source is a clock. Diets like calorie controlled diets, counting your macros or even Paleo do essentially the same thing. They require you to say no to your body until something external tells you when or what to eat. Listening to external cues when it comes to eating can lead to rebound eating, weight regain and potentially obsession with food. All of this is your body's normal response to restriction.
No matter how far advanced we come in the world, no matter how much technology we develop, the one true source of how much, when and what we need to eat, is ourselves. We have within us the innate ability to fuel and nourish our body exactly as it needs to be. Not only that, listening to this innate voice, allowing it to guide our choices, has been shown to improve health, improve body image, support self-compassion and overall, leads to better health outcomes. This innate voice starts with hunger and fullness cues, which we are each born with. The more we listen to external cues telling us when to eat or what to eat, the easier it is for this voice to be lost.
I often get asked if this means that someone is supposed to eat cookies all the time or subsist on pizza and ice cream. This is where the power of exploring and learning what your body needs comes in. You may start eating cookies or pizza and ice cream all the time - especially if you weren't allowing yourself to have them previously. Your body would most likely not feel great after a few days of eating like this. You may find yourself craving vegetables, fruits, whole grains or proteins. Research shows that people who eat intuitively move to greater variety of foods and tend to choose foods that are more supportive of health.
Ultimately, each of us need to find a way to eat that supports our health. Health includes mental health, social well-being and physical health at a bare minimum. While I would never recommend intermittent fasting to achieve a health goal, if you wanted to explore it and experiment with it, I wouldn't tell you not to. I support each person finding what health means for them, while encouraging them to do it in a way that supports all aspects of health. For some people, this may mean intermittent fasting and sticking with this style of eating for a longer period of time. At the end of the day, you are in charge of your body and will make your own choices, no matter what I or anyone else says. My job is to allow you to access your own capacity for change and explore what that change might be like, given your life experiences and current health. I'm here to help you explore your health and find your own answers for what authentic health means to you.
What else do you want to know about intermittent fasting?