Intermittent fasting is pretty much exactly what it says it is – you do it every now and then, for lengths of time determined by yourself. Intermittent Fasting is generally done by skipping breakfast, and eating the first meal of the day around 11am or 12pm – but there’s no reason this fast can’t be extended out longer, should you choose.
This generally creates a fasting window of about 18 hours, assuming you’ve eaten dinner at around 6pm the night before. It can be done every day of the week, or only on days that are convenient for you. Intermittent Fasting generally leads to what’s called a ‘compressed eating window’ – meaning you’re left eating your meals in a small window of time (about six hours). This can lead to spontaneous caloric reduction.
Who might benefit from this sort of protocol?
People in a rush to get out the door in the morning. Rather than reaching for a convenient, sugary breakfast like cereal or toast, why not skip breakfast altogether? People who want the benefits of fasting without having to go a day or more without food. Many of the benefits of fasting can be seen in the space of 18 hours.
It would also benefit people who are wanting to lose weight. Insulin levels drop significantly during a fast, which facilitates fat burning. Spontaneous caloric reduction often occurs as well, as it’s hard to eat an entire day’s worth of calories in one or two meals.
People at risk of Type 2 Diabetes, or with high fasting blood glucose. Fasting can help lower blood glucose levels and the corresponding insulin levels, reversing early signs of diabetes.
The 5:2 Diet
The 5:2 Diet was created by British TV journalist Michael Mosley who advocates eating normally five days of the week, and restricting calories to about a quarter of that usually consumed on two days per week. For men, this looks like 2,400 calories on non-fast days, and 600 on fast days, and for women, it looks like 2,000 calories on non-fast days, and 500 calories on fast days. The two days ‘fasting’ can be done on any day of the week that’s convenient for you, and they do not have to be done sequentially.
The number of calories you should eat on non-fasting and fasting days are based on your ‘Total Daily Energy Expenditure’ (TDEE) – or how many calories you burn each day going about your usual business. To work out your TDEE, click here.
Who might benefit from the 5:2 protocol?
- Anyone who doesn’t like the idea of going a whole day without food. 500-600 calories work out to be a fairly normal sized meal, but can also be spread throughout the day as snacks.
Mosley advocates this way of eating for anyone concerned about their dementia, Alzheimer’s, cancer, or diabetes risk.
Fast days can be split up throughout the week, making this eating pattern easy to fit around a busy schedule.
Extended Fasts – 24 Hours Plus
Fasting changes the function of cells, genes, and hormones in beneficial ways. Many biological functions are up-regulated during a fast. Basal Metabolic Rate (BMR) speeds up by about 4%, Human Growth Hormone is up-regulated by up five-fold during a 48 hour fast, and levels of Norepinephrine (also known as Noradrenaline) increase.
What does all of this mean for you?
Your Basal Metabolic Rate – the number of calories you burn at rest – increases without doing any extra activity. You burn more calories without doing more work. Human Growth Hormone facilitates fat burning and muscle gain, meaning you burn fat while sparing precious muscle mass. Production of Norepinephrine keeps you alert, and thinking clearly (once adapted). Programmed cell death (also known as cellular suicide or autophagy) occurs, clearing out waste products from cells and ridding the body of cells that may pose a threat – like pre-cancerous cells.
Who might this protocol appeal to?
- Anyone willing to go through the challenge of becoming fat-adapted (learning how to use fat and ketones for fuel, rather than glucose). This transition can be very challenging for those who have traditionally eaten a carbohydrate-heavy diet.
Anyone looking to free up some time in their day. Not eating means you don’t have to grocery shop, prep food, cook, or eat. This can free up a significant portion of your day for other things.
People who like to experiment! Fasting for 24 hours or more can be very challenging. At first, the feeling of hunger can be intense, and hard to ignore. However, it gets easier with time and practice.
As you can see, there are many different fasting protocols that can be worked into any sort of lifestyle or schedule. Please note, fasting may not be for everyone, and it is important to listen to your own body when experimenting. If you feel light headed, or have a history of disordered eating and restriction you may benefit from simply eating three meals a day and not snacking.