What is intermittent fasting?


Emma Thornton
Qualified Nutritionist (ANutr)
@EmmaThornton
Ask Emma


16 April 2018

What does intermittent fasting mean?

Intermittent fasting (IF) is one of the latest health trends to grip the UK and, with endorsements from the likes of Beyoncé and Hugh Jackson1, more and more people are flocking towards this particular diet as a form of shedding weight and building lean muscle tone. But what exactly is involved with this diet? 

Well, primarily it consists of alternating days of fasting, where your food intake is restricted, and days where you can essentially eat what you want. Many advocates cite that this particular diet is easier to remember and commit to compared to other more complicated diets and that it’s more natural as humans have been fasting for various reasons for centuries. 

However, others still remain unconvinced by these arguments, worried that cutting out food for such a prolonged period of time may lead to unwanted symptoms, such as binge eating and adrenal fatigue, or that it may cultivate obsessive behaviour.

What are the benefits of intermittent fasting?

Let’s start with the purported benefits of intermittent fasting first. There is a surprising amount of health claims associated with intermittent fasting so I’ll be looking at some of the best health claims first and the evidence that exists to support them.

Intermittent fasting can reduce insulin resistance 

Fluctuating blood sugar levels can be a huge problem, particularly when it comes to our output of insulin. Insulin is a hormone secreted by the pancreas and it helps to regulate the amount of sugar (glucose) in your bloodstream. Unfortunately, the higher your blood sugar levels, the more insulin your body will try and produce which can result in hunger cravings or even insulin resistance, a common precursor to diabetes. 

When it comes to this particular problem, intermittent fasting appears to have a positive impact, with evidence showing that it can help to lower your blood sugar levels and consequently, your insulin levels. One study even demonstrated that, while fasting, participant’s blood sugar levels dropped by up to 6%, while their insulin levels were reduced by up to an impressive 31%!

This reduction in blood sugar has also shown to be very beneficial for your metabolism, in the short term helping you to burn more fat, as we shall explore.

Intermittent fasting can help you burn more fat

The most common reasons for embarking on a diet are to lose weight and burn fat and in this goal, the results of intermittent fasting are largely positive. As I’ve mentioned, fluctuating blood sugar levels can result in hunger cravings, which usually lead to sugar, carb-heaving snacking that can have an effect on your waistline.

It also helps that, when you are in a fasting state, your body is more predisposed to burn fat as a way of supplying you with enough energy. This, in addition to a restricted calorie intake, can cause fat loss but more surprisingly, intermittent fasting causes less muscle loss than other calorie restricted diets, making it particularly appealing to those that also work out.3  

Intermittent fasting can reduce inflammation

Inflammation is at the root of many health complaints, from IBD to fibromyalgia to muscle and joint pain. Surprisingly, though, there is research to back up the claim that intermittent fasting may help to reduce inflammation. This is because intermittent fasting can help to decrease inflammatory responses by changing certain genes related to inflammation, although further studies are still needed.4 

Intermittent fasting can help you to live longer

Finally, many claim that intermittent fasting can help you to live longer and it accomplishes this in a variety of ways. Firstly, it’s believed that intermittent fasting can help to reduce oxidative stress and free radical damage although the exact interaction isn’t known yet. It appears that intermittent fasting may help to strengthen cells against oxidative stress, a big cause of premature ageing.5  

Research from the Harvard T.H Chan School of Public Health even takes this one step further. In one study, conducted on worms, restricting their diet maintained mitochondrial network. Mitchondria are the structures in our cells that help to produce energy, although their ability to do so inevitably diminishes with age. This study implies that fasting may help to maintain the function of the mitochondria, extending our lifespan, although further studies on humans are still necessary!6 

Is intermittent fasting safe?

These health claims are all well and good but is intermittent fasting safe? Here at A.Vogel, we’re not big fans of calorie counting or diets that place severe restrictions on food and so far, intermittent fasting falls directly into both of these categories as it doesn’t consider the individual needs of specific situations.

For example men may find intermittent fasting easier than women because they do not experience the same hormonal fluctuations. Throughout the month, menstruating women’s hormone levels fluctuate and this can become more pronounced during menopause. Our demand for certain nutrients, such as iron and magnesium can increase, not to mention we can become more vulnerable to symptoms such as fatigue, which intermittent fasting may exacerbate.

You also have to consider that, at least initially, intermittent fasting can make you more vulnerable to stress.  If you’re not used to missing meals, fasting can increase your levels of cortisol which can trigger a stress reaction, particularly if your cortisol levels remain elevated. After all, being ‘hangry’ isn’t just a myth!7  

What won’t help matters either is that you will crave food more which can lead to binge eating on your days off. During your non-fast days there are no specific limits on what you can’t eat so many participants see it as a chance to indulge those hunger cravings that have been bothering them, sometimes eating sugary carb-rich foods.  

Finally, fasting can also create an unhealthy attitude towards food. You can start to become obsessive about what you are eating, counting every calorie and almost perceiving your fast days as an endurance contest. Not only is this obsessive behaviour extremely unhealthy, it can sometimes place you under additional stress, even affecting your mental health!

Should I try intermittent fasting?

I would never recommend trying intermittent fasting without first consulting with your practitioner or doctor. They will have a better insight into your individual needs and be able to offer you tailored advice based off that. It’s also important that if you are considering fasting, you should keep hydration top of mind – your body may be able to cope without food but it certainly won’t do as well without water!

There are some groups that should simply never try intermittent fasting – diabetics being one example. I also wouldn’t recommend fasting for those over the age of 50 or menopausal women as your body is more dependent on your food for nourishment during this time, not to mention that fasting may upset your hormones and place you under additional stress.

1http://www.longevitylive.com/editors-choice/why-celebrities-practice-intermittent-fasting/

2https://www.sciencedirect.com/science/article/pii/S193152441400200X

3https://www.ncbi.nlm.nih.gov/pubmed/21410865

4https://www.sciencedirect.com/science/article/pii/S0104423013000213

5https://www.ncbi.nlm.nih.gov/pubmed/17291990/

6https://news.harvard.edu/gazette/story/2017/11/intermittent-fasting-may-be-center-of-increasing-lifespan/

7http://www.health.com/nutrition/what-is-hangry

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