Intermittent Fasting

Ever missed a meal? Chances are that you have. Now if you add a little bit of structure to the meal skipping, say miss breakfast so that the time between dinner and the next meal is around 16 hours, then based on the newly popular intermittent fasting diet you may be onto something. Or …. is it just another fad diet?

What is intermittent fasting? #

Fasting is not a new concept. For centuries, people have temporarily restricted their food intake as a means a way of life (our hunter gatherer ancestors) and for religious reasons. Devotees of fasting have long claimed it brings physical and spiritual renewal. 

In the past few years, different intermittent fasting methods have gained popularity. Intermittent fasting is the process of cycling in and out of periods eating and not eating. The different methods are: 

Alternative-day fasting #

This method requires you to restrict all food for 24 hours, once or twice a week. 

Whole-day fasting #

Commonly also known as 5:2. This approach to fasting advocates no food restriction five days a week, cycled with a 500 — 600 calorie diet the other two days of the week.

Time restricted feeding #

Typically, with this one, eat all your daily calories within a shortened period (typically 6 ‑8 hours) and fast for the remaining 14 – 16 hours. You can do every day, or a few times week. 

The research so far… #

The thing to point out early on is that the research on intermittent fasting — or IF — has mainly focused on men, not women, and numbers within these trials have been on the low side. It’s safe to say that researchers are still putting the pieces of the puzzle together on exactly how different types of intermittent fasting affect us, and what may be the best approach for men vs women, which is maybe why there continues to be mixed opinions on intermittent fasting between healthcare professionals. 

One of the primary mechanisms I’ve seen that makes intermittent fasting so beneficial for health is related to its impact on your insulin sensitivity. High levels on insulin over time promote inflammation and fat storage in the addition, hunger is less likely to be experienced as we never really let ourselves get hungry and as a result fat is more likely to be stored in the liver. 

The act of fasting is also believed to cause an immune response that repairs cells and regulates insulin control. Research shows fasting decreases the accumulation of oxidative radicals in the cell, and thereby prevents oxidative damage to cellular proteins, lipids, and nucleic acids associated with aging and disease. 

However, the research has produced some conflicting evidence. For example, a recent review (40 studies) of the literature looked at the impact of fasting on weight loss. They found that intermittent fasting when done correctly (hold on to the word correctly its important!), was effective for weight loss. 

Interestingly, there were no significant differences in blood pressure, heart rate, fasting glucose and fasting insulin with the subjects following intermittent fasting and those following other general healthy weight loss regimes. 

The results also suggested that it was unclear if intermittent fasting was superior to other weight loss methods in regard to decreased appetite and compliance rates. The different modes of fasting as well as the mix of participant characteristics (lean vs. obese) is worth taking note when interpreting these results. 

More high-quality studies including randomised control trials (the gold standard in research) with a follow-up of greater than one year are needed to show a direct effect, and for us to clearly understand who benefits the most from intermittent fasting, and how it should be done for each population group. 

One size doesn’t fit all. #

If you already have a stable and healthy eating pattern (you consistently eat in balance and enough) and you would like to lose weight or optimise your insulin sensitivity then IF could be something you try as you could repeat the benefits. 

On the contrary, if you are already a bit of a faddy and erratic eater then the risk of IF becoming a faddy diet is very high. Time and time again, within my clinical practice, it is common to see people following a feast and famine IF pattern of eating which does more harm than good! There is no point fasting one day and then feasting the next day – it just won’t do you any favours! 

Similarly, more is not better. Even with fasting — moderation is key. It’s not about trying to do as many fast days as possible either. This is called disordered eating. 

In fact, people with a history of eating disorders, or those using medications that require food intake (type 1 diabetics), those still actively growing (teenagers), pregnant or breast-feeding women should not be fasting intermittently. 

The bottom line is that you need to tailor intermittent fasting, taking in to account your age, life style, commitments, sports, overall goals and stage of life, and adapt it when things change. 

For example, women who are experiencing the menopause should tailer their intermittent fasting pattern for each phase of the menopause. During the perimenopause when they are still getting their menstrual cycle their body may find fasting in the first phase (Follicular Phase) easier than in the second phase (Luteal Phase). 

I recommend finding your style. Just as there are different diets and ways of eating, there’s more than one way to practice intermittent fasting. What works like a charm for your best friend might not be the right fit for you, so try out a few different styles and check in with how you feel during each. 

Also remember to listen to your body. Be on the lookout for signs that intermittent fasting may be having a negative impact. Indicators of this could be changes to energy levels, dizziness, headaches, mood, and sudden difficultly with sleep. 

If you try fasting, make sure to ease into it. Make small, gradual changes over several months, rather than drastic ones in a short period of time as it could help to reduce any unwanted side effects. 

You could for example start by ensuring that you have a 10-hour gap between your dinner and breakfasts. Then you can push your breakfast back by an hour until you are up to 12 hours. If you feel good doing this, you could then work to extend this fasting window to 14 or 16 hours.

Finally, keep tabs of the other lifestyle pillars. If you have not slept well and are super stressed then adding in fasting in the mix may not be beneficial for your wellbeing. 

So what does this mean for us? #

There is more evidence building up to show that, for some population groups, there are many benefits to intermittent fasting, however more research is needed for us to fully understand the therapeutic benefits. Plus we are in need of more, better-quality, research for women at the different life-stages over differing lengths of time.

However, within my own clinical practice, many of my clients who follow an intermittent fasting pattern of eating correctly see the benefits in terms of weight loss and improved metabolic health. 

In addition, many of my clients have found that intermittent fasting has been a good tool to allow them to connect with themselves, learn what physical hunger feels like, gain insight in to portion sizes and feel fuller more quickly.

If you are interested in learning more about intermittent fasting or adopting it as a tool to help improve your health, my advice is that you speak to a dietitian or a registered nutritionist.

It is so important that you approach it in as individualised way as possible because to be the most effective, it has to reflect you and work within your life to support you, rather than being a task or a chore. 

A registered nutritionist will have your best interest at heart and will be able to recommend a method of fasting that works specifically for you. 

References

• Patterson et al. 2017. Metabolic Effects of Intermittent Fasting. Annu Rev Nutr. 21;37:371 – 39 
• Tinsley et al. 2015. Effects of intermittent fasting on body composition and clinical health markers in humans. Nutr Rev. 2015 Oct;73(10):661 – 74. 
• Horne et al. 2015. Health effects of intermittent fasting: hormesis or harm? A systematic review. Am J Clin Nutr. 2015 Aug;102(2):464 – 70 
• Ganesan K et al. 2018. Intermittent Fasting: The Choice for a Healthier Lifestyle. Cureus. 2018 Jul 9;10(7):e2947
• Mattson M et al. 2017. Impact of intermittent fasting on health and disease processes. Ageing Res Rev, 39: 46 — 58