Intermittent fasting (IF) is the word that’s been on everyone’s lips in the health and wellness movement during the last decade.
The word ‘fasting’ may sound scary but IF has been practised throughout all of history and with good reason too. The benefits of IF may include weight loss, which is one of the most popular reasons for people to start their journey. There are, however, so many other positives to adopting the IF way of life, including the recent discovery of a process called autophagy (cell renewal). In fact, weight loss is just an added side effect.
IF dates as far back as the ancient Egyptians and Greeks! Due to food scarcity, our hunter-gatherer ancestors ate what they could and faced potential periods of starvation before finding more sources of food. And guess what? They managed to survive and stay strong. Nowadays, many religions are connected to periods of fasting, including the holy month of Ramadan for Muslims and the 40-day fast for Lent in Roman Catholicism.
So, what’s with the recent revival?
Over the past couple of years, more and more respectable doctors who use IF in their clinics to treat patients with type 2 diabetes and obesity have brought IF to the mainstream media. Most notably, Canadian nephrologist Dr Jason Fung MD, British doctor and science journalist Dr Michael Mosley, and Dr Bert Herring MD, a former cancer researcher at the National Institute of Health.
What is intermittent fasting?
An important point to clarify – IF is not starving yourself!
Starvation is the involuntary absence of food, whereas during fasting food is available but you choose not to eat for any period of time. Any time you are not eating – say during your full night’s sleep for example – you are intermittently fasting. IF can be as simple as skipping breakfast (the word itself means “to break-a-fast”), having your first meal at midday and closing your window by 8pm that night. This is known as the 16:8 method.
There are different ways to follow IF. The most popular ones include:
- The 16:8 method
- The 5:2 diet – where you eat as you would normally five days of the week with the fasting window of your choice. On two days you eat only 500 calories. This was popularised by Dr Mosley on the BBC2 Horizon documentary Eat, Fast & Live Longer.
- Eat-stop-eat – once or twice a week you don’t eat anything from dinner one day until the next day (a 24-hour fast).
In order to receive any benefits of IF, 12 hours is the minimum fasting time recommended. This is the time it takes for your body to get into a fasted state, which is when the magic, or should I say science, starts to happen. Some people choose windows such as 20:4, 19:5 etc.
Why do we gain weight?
Dr Fung outlays in his book The Obesity Code that insulin resistance is what makes us fat. When we eat, food is either used immediately as energy or stored for later use. The key hormone in food storage is insulin.
He points out that: “the main problem of obesity is not the calories we eat but how they are spent. And the main hormone we need to know about is insulin.” This is the fat-storing hormone, in fact, its insulin’s job to store fat. Whenever we eat our insulin rises. When we don’t eat, it then goes down and signals to the body to burn our stored food energy (body fat). If insulin levels are higher than normal, they tell the body to store more food as body fat.
Each hormone plays a role.
- Ghrelin – tells us when we are hungry
- Leptin – tells us when we are full
- Adrenalin – increases energy expenditure
- Thyroid – shuts down energy expenditure
Dr Fung says: “we get fat because we’ve given our body the hormonal signal to gain body fat. And those hormonal signals go up or down according to our diet.” The hypothesis that insulin causes obesity as opposed to calories has been proven in the 1993 Diabetes Control and Complications Trial.
We’ve been told that to lose weight we need to eat fewer calories and move more. But this is never sustainable and maybe people lose weight short term but end up gaining it back and, worse, perhaps even more than before. So the question isn’t about balancing calories but insulin.
Dr Fung states: “During feeding, you store food energy as body fat. During fasting, you burn body fat for energy. If you balance those two, your weight will remain stable. If you are predominantly feeding, you will gain weight. If you are predominantly fasting, you will lose weight.”
Autophagy – the real reason to fast!
Most people think that the number one benefit of IF is weight loss, but there is an even more exciting reason! In 2016 Dr Yoshinori Ohsumi won the Nobel Prize in Medicine for his discovery of autophagy, which translates from Greek as “self-eating”.
Autophagy has been described as: “the consumption of the body’s own tissue as a metabolic process occurring in starvation and certain diseases,” which means that the cells in the body are cleaning out and recycling their own tissues when it’s in ‘starvation’ mode. And what stimulates this process? Intermittent fasting!
Researchers have discovered that the process of cell renewal is so beneficial that autophagy is now becoming known as the: “key in preventing diseases such as cancer, neurodegeneration, cardiomyopathy, diabetes, liver disease, autoimmune diseases and infections.” This research suggests that some of the benefits include:
- Providing the cells with molecular building blocks and energy
- Recycling damaged proteins found in cells
- The regulation of the cells’ mitochondria (which are used to produce energy but end up damaged by oxidative stress)
- Protecting the nervous system and encouraging growth of brain and nerve cells
- Supporting heart cells to protect against heart disease
- Enhancing the immune system
- Potentially fighting cancer and other illnesses.
Autophagy is active in your cells but is increased in response to fasting. Studies suggest that fasts between 24-48 hours have the strongest outcomes but, of course, this can sound completely daunting to any newbies. That’s why learning to fast anywhere between 12-36 hours is a good place to start.
What are the other benefits of intermittent fasting?
Aside from autophagy and weight loss, a study in the World Journal of Diabetes found that intermittent fasting in adults with type 2 diabetes improved their markers such as body weight and glucose levels, and it helped to normalise insulin sensitivity.
Another benefit to intermittent fasting includes appetite correction which, for detailed information and advice, Dr Bert Herring discusses in his book AC: The Power of Appetite Correction.
The hormone ghrelin stimulates appetite whereas the hormone leptin sends a signal to the brain when you are full as a message to stop eating. After adapting to IF, the body’s response to hunger changes. Research from the University of Birmingham suggests that after a few days of fasting, the levels and secretion of ghrelin changes and the need for feeding frequently.
That’s right, the body intuitively knows when to stop feeding and will signal when it is full, which will put an end to habits such as overeating. Leptin resistance tends to lead to stubborn weight gain but has also shown to benefit from IF.
But what can I have during a fast?
A clean fast means drinking only plain or sparkling water and black tea or coffee. Although some experts such as Dr Fung do state that adding a little milk to your coffee is okay, there is great debate between other enthusiasts as to whether it hinders your weight loss results (if that’s why you choose to fast) by spiking your insulin. It does depend on the individual, so what may work for one person may be different for another and you’ll need to experiment.
What’s the appeal of IF for weight loss?
IF is a lifestyle and not a quick fix diet. Even though many people tend to combine IF alongside the ketogenic diet, the success of IF depends on the quality of the fasting window and not the choice of foods. That’s right, you don’t need to count calories or macronutrients or ban certain food groups.
This means that a lot of people are able to eat what they love and not change their diet as long as they have a clean fast. Although opting for nutritious whole foods is highly recommended during your eating window if you sensibly want to improve your overall wellbeing.
If you’re considering starting IF then…
Recognise that intermittent fasting is not suitable for children, pregnant women or anyone who has a history of an eating disorder. If you have any serious medical conditions then please consult with your doctor.
We recommend that you discuss any dietary changes with your GP and transition into the lifestyle under medical supervision.
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