What is 16:8?
16:8 is an intermittent fasting protocol which has a daily period of fasting of 16 contiguous hours. This leaves the remaining 8 hours as a time window for feeding.
Although it’s a requirement to not eat during the fasting window, it’s not a dry fast so drinks with zero or negligible calories such as still or sparkling water, black coffee or green tea are permitted. There are some who suggest it’s possible to consume up to 50 calories before a fast breaks, but I would suggest it’s simply easier to go without adding milk or creamers and hold off until the fasting window is complete unless you absolutely cannot have your tea or coffee any other way. You might be able to get away with it, but then again you might not. Your mileage may vary. Caffeinated beverages are also beneficial in reducing the feeling of hunger as well as providing a temporary metabolic boost¹.
Putting 16:8 into Practise
On a practical level, 16:8 can be easily embedded into most daily routines since the fasting period can include hours slept. For somebody who gets 8 hours of sleep each night, that’s half of the fasting window already taken care of. Let’s suppose you finish the last bite of your evening meal by 8pm, fall asleep at midnight and awake at 8am. That just leaves 4 hours until you would break your fast — something which is easily achieved by skipping breakfast. From 12pm-8pm, you would eat as you normally would and then begin your next fast.
One of the main reasons why I’d suggest a daily fast is better for most people rather than the likes of the 5:2 protocol is that it’s simpler and less jarring on the body. With 16:8, you can establish a daily routine and your body only makes the transition into a fasting protocol once whereas 5:2 would have you frequently switching into and out of a fasting day. Also, 5:2 is not time-bound in any given day so it’s less likely you’d get the benefit of long periods of baseline insulin levels (more on that below).
Effectiveness of 16:8
Losing body fat by dietary means is done by using it as a fuel source. In order for the body to switch to using body fat as its predominate fuel source certain criteria are required to be met:
- There’s a demand for energy not being met by what’s being consumed i.e. a caloric deficit.
- Levels of insulin in the bloodstream aren’t high enough to block the breakdown of fat for energy use.
- There is a sufficient quantity of body fat to meet energy needs.
The process of breaking down body fat for use as an energy source is known as lipolysis. The body will only turn to lipolysis when other more accessible sources of energy (such as freshly digested carbohydrates or that which was stored in body as glycogen) aren’t available. One of the key tenets of intermittent fasting is that it allows lipolysis to occur more readily than just calorie reduction without a period of fasting.
Maintaining a calorie deficit doesn’t necessarily mean the body will switch to lipolysis as this only primes the body to seek out additional energy. Creating the demand for additional energy is not the same as satisfying that demand. In order for the energy demand to be fulfilled by burning body fat, a baseline level of insulin in the bloodstream is required because elevated insulin is a known blocker of lipolysis².
What this means is that avoiding frequent increases in blood insulin levels is an important aspect of using body fat for fuel. Insulin is used by the body to regulate blood glucose levels and is released by the pancreas when blood glucose levels rise. Blood glucose levels rise whenever we eat so to avoid insulin spikes we need to simply not eat.
That doesn’t mean we should never eat. The body still requires nutrients in order to function and remain healthy. 16:8 intermittent fasting not only allows a large enough window for the body to enter a fasted state with baseline levels of insulin so that lipolysis can occur³, but it also allows sufficient time to feed the body with the nutrients it needs.
Let’s say your approach to 16:8 means you skip breakfast and don’t snack after dinner (this is my own personal approach). It’s perfectly feasible to be able to fit two meals and a snack into your feeding window. What’s more, it’s easier to sustain a caloric deficit whilst eating larger meals than you would have done previously or choosing more energy-dense foods.
Can you now see why I find 16:8 to be an attractive proposition?
Skipping meals and not snacking after a certain time might sound like a recipe for hunger, but once your body adjusts to this way of eating you’ll find that you don’t feel hungry during your fasting window because your energy demands can be met by your body mobilising its stored energy reserves i.e. your body fat. That is why your body stores fat in the first instance — to be used as an energy reserve.
Intermittent fasting is not a free pass to eat absolutely anything and everything which takes your fancy. After all, food is still a source of energy which our bodies have to process. I’ve been able to both consciously gain weight/fat as well as lose weight/fat whilst intermittent fasting.
The response from people to the news that you’re fasting can vary greatly. In today’s first world societies, the norm is to eat at regular intervals throughout the day so it’s not surprising that people’s responses can include bewilderment and disapproval. 16:8 makes it much easier to fast discreetly, if that is what you wish.
If you’re wanting to participate in social events involving food then 16:8 also makes it easy for you to do so as your feeding and fasting windows can be adjusted to suit.
16:8 is Liberating
As somebody who fasts daily, I very much take a long term view which means I’m not so concerned about sticking rigidly to the same 16 hours every single day. Sometimes, my fasts are longer and sometimes they’re shorter. I’m in this for the long haul so short-term deviations don’t have a significant impact on my ability to achieve my goals.
I use intermittent fasting to provide myself with more freedom as opposed to thinking about it as a control mechanism with which to restrict myself. Daily fasting frees me from clock-watching and calorie counting. Instead, I have an awareness of the feeding and fasting windows I wish to achieve and then I listen to what my body wants in terms of food choices and quantities.
Once established, the 16:8 protocol provides a platform from which one can easily explore other fasting protocols such as longer fasts or one meal a day. In the 18 months I’ve based myself on 16:8, I’ve done dozens of 20 and 24 hour fasts and even went as far as 48 hours.
16:8 intermittent fasting is no longer a thing to me. It’s become my norm and that’s why I recommend it with conviction.
[1]: Acheson KJ, Zahorska-Markiewicz B, Pittet P, Anantharaman K, Jéquier E. Caffeine and coffee: their influence on metabolic rate and substrate utilization in normal weight and obese individuals. Am J Clin Nutr. 1980 May;33(5):989–97. PubMed PMID: 7369170.
[2]: Chakrabarti P, Kim JY, Singh M, et al. Insulin inhibits lipolysis in adipocytes via the evolutionarily conserved mTORC1-Egr1-ATGL-mediated pathway. Mol Cell Biol. 2013;33(18):3659–3666. doi:10.1128/MCB.01584–12 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3753874/
[3]: Longo VD, Mattson MP. Fasting: molecular mechanisms and clinical applications. Cell Metab. 2014;19(2):181–192. doi:10.1016/j.cmet.2013.12.008 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3946160/
