Time-restricted eating, or fasting are trending terms at the moment, and we’ve had a lot of questions about them.
When practised safely and correctly, it’s a very powerful tool for nurturing wellness. Some of the research around fasting for longevity in particular is promising. Here’s what you need to know.
So, starting right at the beginning—what does fasting even mean?
Quite simply, fasting is a period of time where food and drink are not consumed (apart from water—stay hydrated!)
For example, simply not eating from dinner to breakfast is your overnight fast. So fasting is a very natural occurrence you’ll be doing to some extent already.
When we talk about fasting for health benefits though—generally we’re talking about a longer than just an overnight one.
There is some argument around what constitutes a fast, but this can depend on the reasons for your fasting—black coffee and herbal tea during a fast is fine if you’re wanting to improve your metabolic health, but if you’re fasting for gut rest and repair, it’s more effective to stick with just water during your fasting window.
Research shows that the restorative benefits of fasting begin to happen after 12 - 14 hours without eating or drinking.
Evolutionarily—way back when—food and thus calories were hard to come by. In our modern world, food is everywhere (nutrients are not, but that’s another story entirely).
Not only is food available in abundance, it’s also available round the clock. Research is showing that when we eat can be just as important as what we eat in regards to metabolic health, fat storage, repair processes, and inflammation.
It’s hard for our bodies to undertake repair and restorative processes while also digesting food. So, an extended break from consuming any food or drink (apart from water and perhaps black tea or coffee) of at least 12 hours allows space for these restorative phases to occur comfortably and effectively.
Fasting to Support Inflammation
Fasting can be a powerful tool for managing health conditions that occur as a result of systemic inflammation.
By giving our digestive systems a rest, we are also giving our immune systems a rest. Studies are showing a direct correlation between fasting and a decrease in inflammation, even showing long-term benefits for conditions such as heart disease.
The standard modern diet is high in sugary, processed, refined ‘foods’ which are inflammatory, so it makes sense that spending less time eating, allows for more repair time, which in turn will reduce inflammation.
Fasting for weight management
Insulin is one of the hormones that regulates our blood sugar to keep it at an optimal level. It’s released when we consume food—more sugary foods elicit a bigger and faster insulin response. Too much sugar in the blood is not healthy for us, so insulin floods in as a kind of gatekeeper to put it somewhere safer—and that place is in our fat or muscle cells.
Fat is harder to be used for energy while insulin levels are elevated.
Which is where fasting comes in—by managing the time periods we consume food, we are limiting the time we have higher insulin levels, and therefore making more time when we can access those energy stores (burn fat).
Calorie restriction is not the same at time-restricted eating.
It’s crucial that our bodies are still receiving enough energy and nutrients, but strategically and safely moderating when these are consumed, can have significant health benefits.
Fasting for Longevity
Fasting activates many pathways in the body associated with repair and cellular rejuvenation.
Autophagy is the programmed cell death of old and damaged cells, and increased release of stem cells which rebuild new healthy cells.
If you’ve heard of the ‘Keto diet’ you’ll hopefully know about ketones—a molecule the body produces and uses for energy when glucose and glycogen stores have been used up.
Fasting promotes production and utilisation of ketones— especially beta-hydroxybutyrate, an anti-aging molecule that demonstrates the capacity to delay the onset of aging related diseases and improve cellular health and energy.
The benefits of fasting—again, when controlled and done safely—are extensive, really, and even include improved sleep through supporting the regulation of our circadian rhythm—our natural day-night, wake/sleep cycle.
Surprising benefits to time restricted eating have been shown around the circadian rhythm, our natural day/night balance and improvements in sleep.
There are a number of different ways you can access the benefits of time-restricted eating.
Let’s start with the easiest and move through to the more extreme.
Bear in mind, you’re actually doing this to some extent already! You can split the day up anyway you like, common ones are:
Please note, these are all guides. Adjust and adapt to life your body, and lifestyle. Listen to your body—something isn’t necessarily right for you just because you have chosen to do it.
12:12 12 hours fasting, 12-hour eating window.
Naturally accommodates breakfast, lunch and dinner.
16:8 15 hours fasting, 8-hour eating window
Naturally accommodates two main meals, perhaps breakfast and lunch, or lunch and dinner.
20:4 20 hours fasting, 4-hour eating window
Naturally accommodates one meal a day (commonly referred to as OMAD).
72 hours and more. Done for medical benefits with appropriate supervision.
So with all that in mind, where should you start?
Keep it simple, and do it consistently! Progress steadily as you get used to it.
Build on your natural fasting window that occurs when you sleep. Say you stop eating at 8:00PM and don’t eat again until 8:00AM the next day—you’re doing a 12 hour fast without even thinking about it.
Begin with shifting your natural 12:12 routine, to 16:8—push your breakfast out, either skip it entirely and eat a little more at lunch time, or combine your lunch and breakfast meals (brunch doesn’t have to be on a Sunday!). Optimally, have an earlier dinner, too.
Check in with yourself each day—
- Do you feel different?
- How’s your sleep?
- How’s your skin?
- How’s your appetite?
- How did this schedule fit in with your lifestyle?
Fasting with medical conditions
Like anything new, start slowly and pay attention.
Also anyone with diabetes—both types 1 and 2—gout, eating disorders, pregnant women, and children should not fast without medical supervision.
Can I take my supplements while fasting?
Nutrients better are absorbed with food. Some supps can make you feel nauseous when taking on an empty stomach. So while you can take your supps while you’re fasting, we recommend taking them with food.
The best way to fast is in a way that suits your lifestyle.
If you have dinner with your family every night, then don’t have an eating window between 8am and 4pm.
Is fasting safe while breastfeeding or pregnant?
There is limited research around fasting pregnancy and breastfeeding. We recommend playing it safe and sticking to regular eating hours, or an eating window or no less than 8 hours.
Fasting and exercise
This depends massively on your eating window, lifestyle, stress levels, schedule, what kind of exercise you’re doing. The short answer is—unless you’re doing an extended fast under appropriate supervision, or high levels of strenuous exercise—work out the way you normally would if you weren’t fasting.
Fasting Resources if you want to take a deeper dive:
Dr Jason Fung is one of the world’s leading experts in fasting.Practical Fasting: The Use of Therapeutic Fasting in a Clinical Setting is a compelling talk by Megan Ramos that delves into the more serious health outcomes from supervised fasting.