Intermittent Fasting Guide
Intermittent fasting is quickly becoming one of the most popular eating strategies for those looking to lose fat. It’s a dieting tool centred around eating patterns rather than specific foods you should eat – but is it a fad? Or, an effective strategy to assist in long-term weight loss?
Rather than specifying what foods you should be consuming, Intermittent Fasting, or IF, specifies when you should be eating – it involves windows of eating and fasting each day. Put simply, in a 24h or 7 day period you eat for x amount of hours/days and fast for x amount of hours/days.
This type of eating pattern, or strategy, has its roots in World History; Ancient Man didn’t have the access to food that we enjoy today, so would go for long periods without eating in between successful hunts. Modern humans eat three meals per day for cultural and practical reasons, which have evolved as we have evolved, rather than for biological reasons. Fasting is, historically, a normal eating pattern for us human folk, so is, in essence, not a new concept.
How does intermittent fasting induce weight loss? By reducing the amount of time available for you to eat, theoretically increasing your chance of being in a calorie deficit...yep, you got it, this is simply a means to create that caloric deficit I talk about so much.
How to Intermittent Fast
There are numerous approaches for intermittent fasting; all have eating and fasting windows and all can elicit a calorie deficit. The three most common strategies are:
5:2 Diet
Here the individual eats 500-600 calories for two days per week, the days should be non-consecutive, so maybe a Monday and Thursday, for example. On the other five days, they eat as they normally would. I am not a huge fan of this, as it would be quite easy to overeat on the non-fasting days to the extent that it counteracts the 2 days of deficit. It’s an average calorie deficit over time that elicits weight loss, so, for me, there are potential holes in this approach. That being said, I do know from experience, that this approach has worked for many people.
Eat-Stop-Eat Diet
This strategy involves a 24-hour fast one to two days per week alongside normal eating for the other five to six days. My take on this is similar to the 5:2 method, it’s very open to periods of over-eating during the non-fast days which can undo all the hard work of the fast.
16:8 Diet
This involves a fasting window of 16 hours per day, with just 8 hours available for eating. This approach is nearest to how most of us eat now. For example, an 8-hour eating window could be from 10 am - 6 pm, therefore, one would simply need to avoid eating in the evening and then skip breakfast. There is, of course, the potential for overeating during that 8 hour window, however, because that window is smaller than the other two methods and the fast time is lower, you would be less hungry and less likely to consume enough to counteract the fast. It’s possible, for sure, but this out of all the approaches seems (to me) to be the most practical and I have seen this work when implemented well.
During your fast windows for all of these approaches, you can drink water, tea and coffee (coffee is great as it helps to control hunger) and you can take vitamins.
The appeal of Intermittent Fasting, for many, is that it really is this simple. You abide by the fasting windows and that’s about all you need to do. You go about your daily life exactly as you did before, just keeping within those set eating and fasting windows. I can therefore see why it’s so popular – its simplistic nature.
Does Intermittent Fasting work for weight-loss
Theoretically, having a shorter window for eating or reducing the calories you eat for certain periods, should elicit weight loss via the creation of a calorie deficit. But what does science tell us? In short, the efficacy varies.
A Review by Nutrition Reviews, which examined several other studies on Intermittent Fasting, found alternate day and whole day fasting to be effective in eliciting a 3-9% loss in body fat over a 3-24 week period, but stated that research on time-restricted eating was limited. However, a Randomised Controlled Trial by The Journal of Translational Medicine found that the 16:8 diet yielded better fat loss results than a normal eating pattern when studying the impact on resistance-trained males.
What does this tell us? That science does support intermittent fasting, to varying degrees, and that more research is needed and will likely be winging its way to us soon. Watch this space.
Intermittent Fasting Health Benefits
Although fasting has been around since the dawn of humans, research is still really in its infancy. The majority of studies, in regards to health benefits, have been conducted on animals, so thorough human testing is required before we can have any concrete conclusions.
We do, however, have sufficient research to evidence a strong correlation between Intermittent Fasting and weight loss as well as the following other health benefits observed in human studies:
Reduced inflammation - A Clinical Trial by Free Radical Biology and Medicine found that IF significantly reduced indicators of inflammation and offered rapid and sustained beneficial effects on the underlying disease process in individuals with asthma
Reduced risk of disease - As with any effective weight-loss strategy, the risk of diseases impacting the heart and cardiovascular system can be reduced. This is supported by a Study from The American Journal of Nutrition, which looked specifically at alternate day fasting and found positive results.
There are other publicised benefits, but these are based on short-term studies or/and observational research and openly state that more research is needed before strong conclusions are made – for that reason, they are not cited in this article.
Intermittent Fasting Side Effects
From the research conducted, Intermittent Fasting is a safe weight-loss strategy – our cultural pattern of eating three meals per day has been brought about due to social evolution, rather than a safety need.
That being said, there are some individuals who should avoid this strategy. If you are underweight or have a history of eating disorders you should speak to your GP before undertaking a fast.
There are some anecdotal reports of negative impacts on women, issues such as menstruation disruption and fertility issues; more research is needed in these areas but females should be mindful of this and monitor their health closely when undertaking such a plan. For that reason, I would not recommend you fast when trying to conceive or during pregnancy/breastfeeding. It’s highly unlikely that there will be research on women who are at these stages in life, so this will likely be a constant unknown.
One of the biggest known side effects of fasting is, of course, the feelings of hunger. Our bodies aren’t accustomed to fasting for large periods and we will therefore feel hungry. From my experiences, after the first few fasts, this does get easier but for many people, this is an undesirable side effect and one that is far more extreme than if following a flexible, calorie-controlled diet which will also yield effective fat loss.
Intermittent Fasting has worked for many people, in fact, I’ve had many clients who have implemented IF and had great results as this suited their lifestyle – that’s the key here...generally speaking, you need to find, research and trial an approach in order to find what works for you.
A Parting Shot
In summary, Intermittent Fasting is safe, simple, can elicit weight loss and can improve health markers but research is limited in humans, therefore, fasting should be avoided by some individuals and women should fast with caution. But, putting the science to one side, I have to admit that it’s not something I would recommend to my clients. Why? Because it doesn’t educate us.
To me, IF is a short term fix to a long term situation. It doesn’t educate us on the optimal foods to eat, how much protein to consume, what are the healthiest types of fat, how many calories we need to maintain, lose and gain weight and it doesn’t introduce lifelong healthy habits. Let’s put this into context, you implement IF and you reach your goal weight...what next? That’s the problem with this strategy – there is no next. This leaves us vulnerable to returning to our normal habits and regaining the weight we’ve lost.
That being said, for people that are very overweight and feel this is the only weight-loss approach they can adhere to, then they should, by all means, implement it and get their weight to a healthy level – as the immediate health risks of being obese greatly outweigh choosing an optimal long-term weight-loss strategy.
If you do follow an IF method and achieve your desired weight, I strongly recommend you then move to a flexible, macro-based diet which will then allow you to control your diet in line with your next goal. I also absolutely recommend that whatever nutrition strategy you choose, you combine with regular resistance and cardiovascular training, as we should not underestimate the health and aesthetic benefits of regular exercise.