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Intermittent Fasting (IF), ‘the diet that counts time, not calories’, has surged in popularity over the recent years, with IF advocates singing its praises on high!

Are the health claims valid? Is it really the key to fat loss? Or is it just another hyped-up fad?

What is intermittent fasting?

“Intermittent Fasting, or IF, relates to any diet that cyclically restricts energy intake for a predetermined time period” – Martin MacDonald

In lemans terms, this means that for a prolonged period of a 24-hour day (usually 16-hours over night time e.g. 8pm-12pm) you will restrain from consuming any form of calories and this can be applied to any other form of diet, whether you are vegetarian, vegan, paleo or you simply do not give an F**k what you eat (see food – eat food).

Proposed benefits of IF are a plenty, with a tonne of promising research reporting strong cases of accelerated fat loss, vastly improved health, including a lower risk of cancer, diabetes and metabolic disease, lower blood pressure, better sleep and increased longevity (life span), HOWEVER most IF research has only been conducted on rats!

Recent studies on humans have shown IF protocols to be safe and effective, but is it really the dietary key to optimising our health and how does it work?

So how does it work?

In terms of fat loss, intermittent fasting works in the same way as any other, by implementing a calorie deficit. IF simply makes ‘eating less’ easier as you have less time to eat!

In terms of its numerous other benefits, the mechanisms are a little more complicated, so we will briefly run over the theme of it…

Our bodies are governed by mechanisms called circadian rhythms. These rhythms control our bodies functions by releasing cocktails of hormones at certain points of the day to keep our bodies within homeostasis. A bit like how a computer controls how new cars adjust to the road, based on the feedback it receives from sensors.

These rhythms, which control our sleep-wake cycle, our temperature, digestion etc are greatly affected by our diet (among a host of other things) and therefore can be disrupted by ‘inefficient’ eating patterns. Patterns such as ours today, which differ greatly to that of our hunter gatherer ancestors.

Enter Intermittent Fasting, or time restricted eating, which according to some scientists and nutritionists may better co-inside with our circadian rhythms and the efficient processes of your complicated body clock, thus allowing our bodies to work at its greatest capacity.

What are the benefits?

- Fat loss

First of all, it is unclear whether you will lose more fat using an IF protocol compared with a more conventional eating pattern when both eating patterns contain the same number of calories. The amount of fat lost is due to the calorie deficit, not the IF protocol. IF may simply allow you to sustain a calorie deficit with relative ease for a longer duration than conventional eating patterns, IF IT SUITS YOUR LIFESTYLE.

- Improved muscle retention

Contrary to popular belief, your body will not start to eat itself if you miss a meal. Weight loss studies have actually found that when comparing people using IF protocols to people eating whenever they like. IF participants actually preserved more muscle tissue during caloric restriction than their unrestricted counterparts (Varady, 2011).

- Improved health & reduced risk of disease

IF protocols have frequently shown to improve health markers and decrease risk factors for diseases such as diabetes, heart disease and even arthritis (Muller et al, 2001). Health benefits of IF protocols have also shown to include an improved insulin sensitivity, beta cell production, blood pressure and oxidative stress (Sutton et al, 2018).

- Increased cognitive function and decreased risk of degenerative disease

Although studies are few, many IF advocates report greater clarity of thought, alertness and focus which may be linked to IF’s influence on ketone production in the body. According to Dr Mark Mattson, a professor of neurology at John Hopkins university, fasting has also been shown to increase neurogenesis in the brain, which is the growth and development of new brain cells and nerve tissues.

IF has also been found to significantly reduce inflammation (via means of increased Autophagy, where the body cleans out old and damaged cells), which has been labelled as a leading cause of chronic brain diseases such as Alzheimer’s and Dementia!

- Increased endurance

Although most endurance research has been conducted on mice. Studies have shown remarkable increases in endurance performance when mice were restricted to eating during only 8-10 hours per day compared to mice who were not restricted. These finding need a lot more research however, theories suggest these benefits relate to IF’s influence on mitochondrial biogenesis, where cells produce a greater number of mitochondria, the batteries of our cells.

- Suits busy lifestyles

In today’s world, we are all run off our feet. Work, school runs, university, second jobs, kids’ activities, socialising, hobbies etc all make it harder for us to sit down and actually eat a good meal. This is why convenience meals and snacking has become the dietary norm in the western world. IF counters this by freeing up time, improving cognitive abilities and sleep and allowing us to focus on our daily tasks without interruption until segmented parts of our days when we can allow ourselves to relax and enjoy our food.

General Misconceptions and FAQ’s

- Will I automatically lose fat using IF?

IF is not the key to fat loss. A caloric deficit is. IF is simply a tool that we can use to make sustaining a caloric deficit easier.

- Will I lose muscle?

No. In fact many studies have shown greater lean muscle tissue retention in IF participants during periods of caloric restriction in comparison with participants who did not time restrict eating (Varady, 2011). Some studies have even found increases in lean body mass, even during periods of caloric deficit (relating to %), although the mechanism is not fully understood.

- I thought Breakfast was the most important meal of the day?

There is much outdated research suggesting skipping breakfast may lead to overeating later on in the day, particularly in the evenings. However, IF protocols restrict eating at this time, making it hard to overeat when you have limited time to feed, train and complete your daily tasks within a time restricted window. Sutton et al (2018) actually found a decrease in evening appetite in IF participants. Recent research by Dhurandhar et al (2014) also found that when comparing people who chose to eat or skip breakfast during a period of caloric deficit, no discernible effects were found on weight loss efforts.

- I thought you were meant to eat little and often?

An absolute corker of a nutritional myth promoted by bodybuilders who have to eat frequently in order to consume the excessive number of calories they need to fuel their bodies. Research comparing a 3-meal protocol to a 6-meal protocol in regular people showed no difference in amount of weight lost (Cameron et al, 2010).

- Am I allowed to drink tea and coffee during a fast?

This depends on the level that you want to go to and what benefits are important to you. If you want to use IF as a simple means to control calorie intake, then sure, there would be nothing wrong with a cup of tea or coffee in the morning, maybe even BCAA’s if you are training in the morning. However, these beverages, and anything other than water, will break your fast as they activate metabolites in our livers, and thus you may not experience some of the health benefits associated with longer periods of fasting. More research needs to be done here.

- Can I have a ‘cheat night’?

Luckily, apparently yes! Studies on mice, which included ‘cheat weekends’ found little to no significant disruption in IF benefits between mice who cheated and mice who did not (Chaix et al, 2014).

This serves us well when trying to integrate IF into our social lives as it means once or twice per week we can go out for dinner and maybe eat later than usual, or if something goes wrong at work, we can stay late and not have to worry too much about missing our eating window.

- Should I still count calories?

If you are serious about weight loss, then yes. Remember IF works for fat and weight loss when it is a part of a calorie restricted diet. It is the caloric restriction which causes you to lose weight and it is better to track our intake if we want to be sure we are in a deficit. That being said IF has worked well with people who do not want to track calories as it simply makes it harder to over-eat when we have a shorter time period to consume, thus IF may be a beneficial tool for people who want to lose weight but do not want to track food all of the time. For these people I would suggest tracking calories once to twice per week to ensure a deficit is being applied.

Is it suitable for everyone?

Sorry but no. As always (and forever), there really is no one magical answer to every bodies wants, needs and problems. Although IF is generally safe to the vast population (except pregnant women*) and may be beneficial to the majority, IF is quite a dramatic lifestyle change and may not suit your lifestyle.

This is pretty much the only reason why IF may not be suitable for you, however restricting food for a long period and adapting to hunger is a pretty big reason and may not be applicable if you simply do not enjoy it. That being said, many IF case studies have found that the discomfort relating to feelings of hunger do subsist after a few days as the body adapts to a new eating protocol and missed meals.

Remember a sustainable diet is something we must find relatively easy and enjoyable.

People who usually find IF protocols useful are people with a busy lifestyle who have little time to eat during the mornings. IF may also be more beneficial to people who train during the afternoon and early evening compared to those who train during the morning as it may be beneficial to surround training with ample nutrition to support psychological needs, energy and recovery.

*Pregnant women should not attempt IF as there is very limited research outlining the effects of fasting during pregnancy. Restricting eating times, fasting for long periods and restricting caloric intake may cause increased stress on a women’s body during pregnancy and therefore should be avoided.

Methods of Intermittent Fasting

16-hour Overnight Fast

One of the most popular forms of fasting and a great protocol for those who are busy in the mornings and training during the afternoon / evening as it allows for a greater food intake around training times. Follow these guidelines every day with 1-2 cheat days per week I needed.

5:2 Diet

Another popular form of fasting, mainly due to the amount of get rich quick books put out in the last 5 years. This form of fasting earned itself some bad stick through the bad practise described in these books, however if you get it right, this could be an effective tool in your fat loss arsenal. Eat at maintenance level for 5 days followed by 2 days on a very low number of calories to drop you into a deficit on average. This could work if you have two particularly busy days or days where you do not train.

Alternating Days

Eat one day, fast the next and repeat. This method may seem a bit more extreme than the others, however it has been used extensively in research and has produced very impressive weight loss results.

Single day Fast

This method proposes a single 24-36 hour fast, once per week. Its proven health benefits have been greatly researched and it requires less of a deficit per day over the rest of the week to sustain a negative energy balance.


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