The pros and cons of intermittent fasting

Ah, intermittent fasting.

Depending on who you speak to it is either the holy grail of weight loss or longevity… or just another fad diet.

Going without food for extended periods of time might not sound like fun, but it has been part of our history for as long as we’ve been human. Just a few hundred years ago we would regularly go hungry in times of food scarcity, and even in today’s world billions of people fast for religious or spiritual reasons.

So whilst the practice of intermittent fasting is certainly nothing new, the concept of purposefully avoiding food for hours or even days is only just exploding in popularity.

And if the advocates are to believed, intermittent fasting is the secret to greater productivity, a stronger immune system and a dramatically reduced waistline.

But is intermittent fasting really the miracle cure it is made out to be?

Or would you be happier and healthier without it?

Let’s take a look.

What is intermittent fasting?

By definition, when we are not feeding we are fasting. This includes the time we allow between meals and even the time we are asleep. Intermittent fasting is simply a strategy that looks to extend the periods of fasting and reduce the periods of feeding. Intermittent fasting is often practiced for health, longevity, weight loss, or even spiritual and religious reasons.

The most common types of intermittent fasting include:

Time restricted eating: This method of fasting involves limiting your food intake to within an allocated window of time during the day. This could be 14:10 (14 hours fasting, 10 hours eating), 16:8 or even 20:4. Typically this would include time spent asleep and would involve delaying breakfast until later in the day.

The Warrior Diet: This diet usually involves eating just fruits, nuts and seeds during the day and then eating one large meal at night.

5:2 Diet: For five days of the week you eat normally. For the other two you restrict your caloric intake to between 500 – 600.

24 hour fasting: An extended period of fasting, usually lasting from dinner the previous evening all the way through to dinner the next day.

As mentioned earlier there are also many people who fast for religious reasons, such as the Muslim tradition of Ramadan.

And there are people that practice extended periods of fasting for medical or spiritual reasons, but for the purpose of this article we will focus solely on intermittent fasting for now.

The benefits of intermittent fasting

There are a number of benefits associated with intermittent fasting, with a growing amount of research emerging on different ways it can impact our health. Here are the ones that you need to know:

Intermittent fasting may aid weight loss

One of the major reasons people turn to intermittent fasting is in an attempt to lose weight. There are a number of research papers conducted on intermittent fasting and weight loss, with many of them showing positive results.

One example is a 2015 clinical review that looked at the effects of alternate day fasting on fat loss. The review showed that subjects lost an average of between 3.5 and 5kg of body fat over a 3 – 12 week period, and also showed a reduction in their triglyceride and cholesterol levels¹.

However what is less clear from these studies is whether it is the intermittent fasting itself that boosts weight loss, or simply the caloric restriction that results from it. By reducing the amount of time during which you eat it becomes much harder to consume as many calories. It is easy to eat three large meals and snacks in a normal day, but trying to cram all of this food into an 8 hour window is much harder.

So whilst intermittent fasting can be a great aid to weight loss, I am yet to be convinced that it is the mechanism of fasting itself causing the fat cells to melt away. Rather, intermittent fasting is simply an effective way to control the amount of calories you consume in a given day or week.

Furthermore, it is also important to keep in mind that there are two issues with the studies on intermittent fasting and weight loss:

1. The vast majority of them are short term studies conducted over a period of weeks and months rather than years. This means they do not take into account the long term impact of intermittent fasting on metabolic health and weight management.

2. The studies do not consider muscle loss, so it is unclear whether the intermittent fasting is also eating into your hard-earned muscle stores as well as fat. Depending on your metabolic health this is something that will be very different from person to person.

The bottom line is, intermittent fasting can be an effective aid to weight loss, but it is not the ‘holy grail’ it is often made out to be. The most important elements of weight loss will always be the quantity and quality of food that you are consuming.

Intermittent fasting may increase human growth hormone

Human Growth Hormone (HGH) is produced in the pituitary gland of the brain and plays a vital role in the growth and repair of healthy human tissue in the muscles and even the vital organs. Human Growth Hormone also accelerates lipolysis, the breakdown of lipids (fat cells) into glycerol and free fatty acids (energy).

If you are a sports fan you have probably heard of athletes illegally supplementing with HGH in order to increase performance. Thankfully there are a number of ways we can naturally increase HGH, including through resistance training and getting plenty of sleep.

There is research to suggest that intermittent fasting may also help to increase our HGH levels. However, the significant benefits appear to occur after extended periods of fasting (between 2 – 5 days) so it is important to conduct these fasts under strict supervision².

There is also evidence that intermittent fasting decreases insulin levels as we extend the period we go without food. Research suggests that insulin spikes can disrupt our natural growth hormone production³.

However there are also many other ways to manage insulin levels including eating a diet rich in protein and fibre, and practicing resistance training.

Intermittent fasting may increase autophagy

The thing I like the most about intermittent fasting is the potential to increase our body’s natural cellular detoxification process, also known as autophagy.

This process involves the cells breaking down and metabolising dysfunctional proteins that accumulate over time. It is a natural waste removal process that has been shown to provide protection against various diseases including cancer.

Furthermore, fasting has been shown to create beneficial changes in our gene expression which relate to increased longevity and prevention against disease.

But if fasting is not for you, there are also certain foods that have been shown to produce these same beneficial changes in gene expression; including green tea, kale, apple, cocoa, parsley, turmeric and blueberries.

Intermittent fasting may protect your brain

In addition to the benefits at a cellular level, there is evidence to suggest that intermittent fasting may protect the health of your brain.

Firstly, there is evidence that links fasting with a decreased risk of Alzheimer’s disease. This is due to a number of mechanisms including decreased inflammation, lower insulin resistance and increased cellular renewal that result from fasting.

Furthermore, there are a number of animal studies that link fasting with improved biomarkers of brain health, including research on mice that found fasting improved memory and learning function.

Additional research on required in humans to confirm the validity of these studies.

Intermittent fasting may improve digestive health

Another reason I like fasting is because of its ability to improve digestive health.

Most people spend their days constantly grazing and snacking which mean their digestive systems are working overtime to break down all the food they eat. By allowing longer periods without food we give our guts time to rest, restore our enzyme pool and repair the gut lining, all of which contribute to healthier digestion.

These benefits can also be achieved by allowing more time between meals and eating earlier at night.

The downsides of intermittent fasting

By now you’re probably starting to fall for the hype of intermittent fasting, right? But before you set your stopwatch to calculate your first time-restricted eating window, keep in mind that intermittent fasting isn’t for everyone. In many cases, it may actually be doing more harm than good.

The first downside of intermittent fasting is that extended periods without food are a stressor to the body. When we go without food, our body secretes higher levels of the stress hormones cortisol and adrenaline. This is a natural survival mechanism designed to make you more alert in times of food scarcity so you could hunt or forage for food more effectively.

However, continuously putting our body in a high stress state is very taxing to our nervous system and can lead to symptoms of burnout or adrenal fatigue; such as low energy levels, decreased hormone function, low body temperature and even depression.

Many of us are already dealing with high stress jobs and lifestyles, meaning adding additional stress to the equation is not a good idea.

Extended periods of fasting may also decrease our leptin levels and slow down our metabolism¹⁰. This is another survival mechanism designed to help you conserve energy and burn less calories in times of food scarcity.

Furthermore, if you are an athlete or have a hard training schedule, I would recommend against intermittent fasting. Your body will be burning through a lot of glycogen and your demand for amino acids will be much greater than a sedentary person, so replenishing your energy reserves regularly with quality sources of protein and carbohydrates is advised.

Lastly, if you have suffered from an eating disorder or struggled with a negative relationship to food in the past, I would steer clear of intermittent fasting as it is ultimately another form of restrictive eating.

Signs IF isn’t for you

If you are experiencing symptoms of high cortisol or reduced adrenal function I recommend avoiding intermittent fasting like the plague. These symptoms include:

Low body temperature
Cold hands and feet
Difficulty waking up in the morning
Difficulty falling asleep at night
Waking up multiple times at night
Brain fog / chronic fatigue
Poor immune function
Low libido
Low blood sugar
Dry skin

Typically the reason most people feel so good on the first few months of intermittent fasting is because they are tapping into their adrenal stores for energy. This is what results in the euphoric, productive feeling that people experience when they first try intermittent fasting.

However over time your adrenals start to take a beating and you begin to run into some of the health concerns I mentioned earlier. When adrenal function is compromised it can take a lot of rest and recovery to heal.

This is why I often recommend short term periods of intermittent fasting for those looking to give it a try. This way you can access the benefits we spoke about earlier without putting your body in a state of chronic stress. A few days of intermittent fasting each month are plenty, rather than doing it every single day.

Also, if you do try intermittent fasting, make sure to listen to your body and not the clock. If you wanted to fast for 16 hours but by hour 14 your blood sugar has dropped and you are experiencing intense hunger, get something to eat. Your body knows more about what it needs than your stopwatch.

Why I don’t recommend intermittent fasting to most people

Whilst intermittent fasting can be a useful tool for some, the majority of people are still mastering the basics of a healthy diet and don’t need to worry about it.

Most people I speak to are still struggling to eat enough fruits and vegetables, drink enough water and sleep for 8 hours each night. The last thing they need to be worrying about is condensing their feeding time into a 6 hour window.

The best ‘diet hack’ that you can make for your overall health and longevity isn’t intermittent fasting. It is to eat a healthy balance of protein, carbohydrates and fat and to fill your plate with as many brightly coloured fruits and vegetables as you can at each meal.

Focus on doing that three times per day, every day. And if you still want to talk about intermittent fasting, we can revisit it in six months time.

The other reason I don’t often recommend intermittent fasting is because most people are stressed up to their eyeballs.

Earlier we spoke about how long periods without food are stressful to the body. So if your busy job, hectic lifestyle and one billion iPhone notifications mean that your stress levels are already through the roof, the last thing you need is intermittent fasting adding another shot of cortisol to the cocktail.

Again, none of this is to say that intermittent fasting doesn’t work. It is simply a tool that has to be used by the right people, at the right time, for best results.

Do I fast?

So by now you’re probably wondering if I practice intermittent fasting myself.

The answer is… yes and no.

I don’t deliberately go for extended periods without food. I don’t set a timer, I don’t eat within a restricted time window and I don’t ignore my body’s natural hunger signals.

However I do usually eat dinner fairly early in the evening, most days finishing between 7 – 8pm. I don’t like to eat too late because I don’t sleep as well when I go to bed feeling really full.

And I don’t eat breakfast when I first wake up. Instead, I have some lemon water and a green juice and usually eat my first meal around 9 – 10am.

All of this means that whilst I’m not intentionally fasting, most days I am having a 13 – 14 hour window without food.

But this form of ‘fasting’ is never forced and isn’t about abstaining from food for a strictly allocated amount of time. It’s just about listening to my body. If the restaurant reservation is later than usual, I’ll eat. If I’m hungry first thing in the morning, I’ll eat. If if I have friends over and we’re baking chocolate chip cookies at 10pm, I’m sure as hell gonna eat.

I don’t believe that any form of dieting, be it intermittent fasting or eating more whole foods or even going vegan, should be about restriction. It should be about the wonderful abundance of food that you can eat, and the benefits that the lifestyle brings.

So if intermittent fasting makes you feel great, fits in with your lifestyle and allows you to remain healthy and active… keep going! Just make sure you keep an eye on how your body feels when fasting and don’t be so ‘locked in’ to IF that you refuse to adjust things even when the demands of your body start to change. Just because IF is right for you now doesn’t mean it will still be right for you in six months time.

Or, if intermittent fasting feels too stressful, leaves you feeling exhausted or even means you have to turn down social occasions… don’t worry about it. IF isn’t the miracle cure it is often made out to be and you can be perfectly healthy eating three regular meals per day.

(and a late night cookie every now and then.)

Catch you on the next one,

Josh

Comments (1)

By Jamie Harrison-Payne posted on October 22, 2018

Great article Josh! I’m not a fan of IF and don’t reccomend it to my clients. Like you say, people have enough to worry about in their every day lives without having eating windows to worry about. It’s still a diet which involves restriction which people find hard to stick to. Your final Paragraph sums things up Perfectly. Just eat intuitively and restriction free.

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