Intermittent fasting comes in all shapes and sizes. From the ‘5:2’ diet, to alternate day fasts or longer periods without any energy intake.
What I’m going to talk about is the form of intermittent fasting which can also be called time restricted eating, the 16:8 eating pattern.
In this pattern calorific intake is not limited, the eating hour window is. What this means is you only take in calories during a consecutive 8-hour window in the day, with only zero-calorie fluids such as black tea or coffee, herbal teas or water, in the other 16 hours.
There is growing scientific evidence supporting health benefits with this pattern of eating.
Studies were initially performed on animal models. Professor Satchidananda Panda is a well renowned researcher in this field. His studies show that anything from a 12-hour eating window can be beneficial for our health, with greater benefits at 10- and 8- hour windows.
The issue is that with our modern lifestyles many of us are eating round the clock, and never giving our guts a break. Keeping to a shorter time window of eating helps restore circadian rhythms, aiding sleep, metabolism, digestion and so much more.
- Improved production of gut-bug Akkermansia muciniphila (weight control, insulin sensitivity) & increased gut microbiome biodiversity.
- Reduced inflammation
- Improved blood glucose control
- Improved appetite signalling, in turn helping to create habits of mindful eating.
- Improved mitochondrial function
- Aids the process of autophagy – a regulatory mechanism which breaks down dysfunctional components of cells and recycles them.
Although there is no formal restriction on the number of calories you eat in a day, those limiting energy intake to an 8-hour window often reduce their overall calorie consumption. In turn this can lead to weight loss and improved blood pressure control. To be eating a healthy diet, it is still advisable to be mindful of what you eat within the 8-hour window. It remains preferable to achieve other goals, such as eating your ‘5-a-day’ and a non-processed diet, and sticking to recommended calorific intake for your age, gender and lifestyle.
Whilst animal studies have been conducted, gold-standard randomised control trials in humans researching time restricted eating are limited. This means generalisation of these findings are yet to be shown. What this means in reality is that whilst time restricted eating is promising, more evidence is needed before formal conclusions can be drawn.
- Choose a time-scale that suits you – this way most likely to feel less intrusive and stick to it.
- Some people like having breakfast as soon as they wake up whereas others don’t. If you’re someone who can hold off for a while this might help you, if not you can choose an earlier eating window.
- It’s potentially better to have an earlier eating window in line with your circadian rhythm, but the priority is choosing a time window that suits your lifestyle so you will stick to it.
- Stick to this time frame – body will get used to it and likes routine.
- Black tea/coffee and herbal teas OK when fasting and can help if you’re feeling peckish.
- Get a fasting buddy!
- You can get out your competitive side if need motivation to keep to your eating window.
- Gradually increase the fasting window if can’t go straight into 8 hours.
- If you’re feeling hungry, remember to ensure you’re getting enough protein and fibre, these tend to be the things that keep you satiated. Most of us in western societies aren’t getting our recommended daily intake of 30g.
- Don’t panic if you miss a day or two, food is so much more than fuel, it’s culture and community and an expression of love. Staying within a 12-hour window is beneficial, but if you don’t make the 8, don’t worry. Find a balance that suits you.
- Professor Satchidananda Panda advised you can get the benefits of time restricted eating whilst being flexible. Doing the 16:8 for even only 2 months of the year can yield benefits, moving to a 10- or 12- hour eating window thereafter if finding the 8-hour window too much of a challenge.
- Another option if 16:8 is too much of a challenge every day is to have an 8- hour eating window five times a week and on 2 days sticking to 10 or 12 hours. If this works for you and is more achievable than 16:8 every day, go for it. Animal studies have show that the protective and beneficial effects of time restricted eating were maintained even when access to food was unrestricted for 2 days of the week (Chaix et al., 2014).
- Take your mind off fasting. When I started and sometimes still, the days I find hardest is when I have more time on my hands. When I’m busy at work I can easily forget I’m fasting and the time whizzes past. Distract yourself!
- If you have an active eating disorder/disordered eating or recovering from this it’s best to avoid restrictive eating patterns.
- If you are diabetic, especially if poorly controlled or on medications to lower your blood sugar – discuss with your doctor before embarking on fasting behaviour.
- If you are pregnant or breast feeding it’s best not to restrict your eating window to less than 12 hours.
Hope this helps anyone with queries about time restricted eating or inspires you to give it a go.
Chaix, A. et al. (2014) ‘Time-Restricted Feeding Is a Preventative and Therapeutic Intervention against Diverse Nutritional Challenges’, Cell Metabolism, 20(6), pp. 991–1005. doi: 10.1016/j.cmet.2014.11.001.