I must stress firstly that safety is a big concern whenever you start anything new and I searched for years to find the drawbacks (if any) to intermittent fasting – before I decided it was safe to go full-time with the practice myself. I initially used intermittent fasting for 4-month periods, just to get leaner (normally annually, or twice yearly). But I made sure I underwent health screening tests annually during those periods, to compare health markers and that is what finally convinced me it was safe – in the absence of adverse clinical data and studies. Even in my numerous discussions with endochrinology consultants, general practitioners and weight loss surgeons with whom I work closely on a daily basis (doctors who – by their own admission – do not understand intermittent fasting very well and are not familiar with the data) they all accept that it theoretically cannot be unhealthy – they may suspect it to be uncomfortable, but not unhealthy.
I personally would not publicise a system which I was not 100% convinced is safe and I will never recommend a path of action to other people if I am not prepared to follow it myself. By writing the Handbook of Intermittent Fasting I have endorsed the lifestyle personally, I follow it myself and I think it is the best method of calorie control for the human design.
I have not found any meaningful clinical safety issues around IF in literature or in anecdotes (but I will give a possible reason for a theoretical health risk which I have recently investigated and ruled out completely at the end of this message). It’s nothing to worry about and I’m sure you’ll agree with me on this when you’ve read this article.
There are dozens of intermittent fasting clinical studies and also long-term trials currently underway at the moment, looking at actually pushing towards suggesting to governments that intermittent fasting is the most healthy way for the general population to eat – as a result of the numerous favourable animal studies which have been done and the numerous short-term human studies (and anecdotes).
I’m sure if you scout the internet you’ll find massive communities of people who are using (or just discusing) intermittent fasting and I have never come across a single one of those forum users who claims in any credible way that the practice is dangerous. Some people question its efficacy, some question its practicality, some even question the comfort of the practice – and many people don’t like it. But I have never seen any meaningful claim to have actual evidence of any danger relating to the practice.
I think it’s important for people to be aware of the difference between “fasting” and “starvation.” “Starvation” relates to a lack of adequate nutrition and “fasting” is about calorie restriction without a compromise on nutrition. Diet must be balanced when you fast (even if you restrict calories). You don’t compromise on nutrition when you intermittently fast, just on excess calories (especially if you are exercising or bodybuilding). Also, scientific literature clearly states that:
“…the only scientifically proven method for extending the lifespan of any living organism is controlled starvation – without malnutrition…”
Nobody has been able to find an equivalent alternative to (or to disprove) this statement.
I think if you don’t have complete confidence in intermittent fasting yet, but you are keen to continue fasting and related practices, my suggestion is to vary your fasting periodically – based on your physical condition. If you have reached a static level and have reached your goals for leanness, weight loss and muscularity – then it may be a good idea to switch from, say, a total abstinence (water fasting) routine to a fruit fasting routine. On a fruit fasting routine you simply calculate a portion of fruits which will equate to about 20% of your full calorie requirements for the days when you do eat – and you can then spread those fruits across the full fasting period (or part of it) in any way you see fit. You can eat them as small meals (at breakfast, lunch and dinner) – or you can eat them in just one or two meals – you choose.
Intermittent fasting is very flexible and fruit fasting is as effective as total abstinence fasting – if done correctly. I went onto an ADF fruit fasting routine over the Christmas holiday period (including a holiday road trip around Scotland with my family) and on the ‘eating days’ I only generally ate Burger King and McDonald’s food (and puddings and such like, I’m ashamed to say). But because I had switched from daily fasting (for 19 hours each day) to alternate day fasting, I was still able to confuse my metabolism and I actually lost 5 lbs of fat in that period. I did not change my workout routine during that 3 week period, I stuck to my normal home-based fitness routines (even when living in hotels, etc). My body actually looked better at the end of it all and a clinical body fat measurement at a private hospital and at a gym showed that I had reduced from 9% to 7% body fat in that time (for what that sort of measurement may be worth).
The reason I changed to alternate day fasting when I went on holiday (which I do during most ‘longish’ holidays) is because it is easier to regulate your appetite on an alternate day fasting protocol than on a daily fasting one. When you get up in the morning after a fasting day (if using alternate day fasting) your appetite is pretty much the same as if you had eaten supper the previous evening. Alternate day fasting is much better for appetite regulation than daily fasting, which is why I recommend it for people with serious disciplinary issues around eating, or for people who binge, or for people who are extremely overweight. But it also works for people who want to rule out failure with weight control.
If you do alternate day fruit fasting I would suggest a basic regime, such as having an apple or two every four hours or so. It doesn’t need to be exact. You can eat every 4-6 hours if you want some sort of structure, but structure is not essential, what counts are total calories eaten during the fast. I would suggest small meals every few hours if I had to make a recommendation. If you really want a change try some sort of low calorie protein meal instead of fruit – an egg, some ham, some meat and vegetables – just have an idea of how the total calories compare to your total daily requirement (protein also suppresses appetite, like fruits).
I suggest fruit fasting – rather than eating other meals or protein – because it’s easier. Once you start straying towards ‘real food’ you risk losing track of calorie restriction and that becomes a chore. Fruits are easy. Use low calorie, non-starchy fruits and you should have little trouble ‘fasting’ (an internet search for “low calorie fruits” or “low GI fruits” will get you all the information you require about which fruits to use, but if in doubt use just apples – they are best).
In addition, fruit fasting is great because it allows you to drink more water through the day – the fruits (especially apples and pears) are fibrous and they curb appetite really well and they bulk up your bowel ‘fullness’ by holding on to more water, for longer. This brings me back to the safety aspects of fasting. Drinking lots of water on a total abstinence water fast is less comfortable than on a fruit fast, because – if you are not eating – you risk literally ‘diluting’ your body’s cells if you overdrink water (this is referred to as water toxicity). Water toxicity is rare and usually only happens to endurance athletes who hydrate with pure water and sweat out a large percentage of their body weight in water and salts. It also happens to people who are forced to consume unnaturally large amounts of water in one sitting (such as some misled university ‘initiation rites’ which are the main documented cases of water toxicity in the literature).
It is not a risk for an average person, drinking less than a litre of water every few hours. However, long duration (many days) water fasting can (theoretically) lead to this ‘dilution’ of the body’s cells and tissues – forcing them to absorb too much water due to a loss of salt from excessive urination and/or sweating. That is why water fasting for days on end is regarded as being dangerous – if done without experienced supervision (the natural loss of salts through sweat or urine can alter the cellular osmotic balance to the extent that water starts to build up in the cells). This is not good for any tissues – but is especially dangerous for the brain. Such an event would probably lead to sudden death.
Here’s some extra detail from the internet:
I did some searching on the internet and found a good entry on Wikipedia. It is still covered completely in my explanation in my message above, but it confirms what I had already said about “water poisoning.”
You’ll also find the following case under the list of known water toxicity cases near the bottom of that Wikipedia entry:
“…In 2008, Jacqueline Henson, a 40-year-old British woman, died after drinking four liters of water in under two hours as part of her Lighter Life diet plan…”
Lighter life is just a ‘dressed up’ version of fasting and intermittent fasting (but it charges a lot of money, incidentally, for the privilege of being supervised) and it also happens to be the most successful commercial weight loss programme in Britain (I think because it is based on intermittent fasting). That may explain why somebody would mistakenly think intermittent fasting could potentially cause sudden death. The woman referred to above would have been fasting for a number of weeks under the Lighter Life protocol – without any soilid food – and, for the reasons I explained above, drinking excess water after a long water fast may lead to water toxicity (due to a long period during which electrolytes are not replenished or balanced). A 24 hour intermittent fast cannot accomplish this same thing.
Just for the record, instead of paying for the Lighter Life Diet this can be replicated by fruit fasting – as explained in my earlier message. The fruits balance the electrolytes when people fast, so toxicity is not easily possible under those conditions. Lighter Life uses expensive nutritional powders – with hardly any calories – but which contain lots of salts. People are known to fruit fast for even 4 months at a time and can even compete in triathlons during that time because fruits will balance electrolytes when you fast. The difference is between fruit fasting and water fasting. You really should not water fast for more than a few days in any single stretch (and under supervision) and intermittent fasting does not recommend longer than 36 hours of any type of fasting (usually about half this figure, actually).
Having said that, Lighter Life is great for weight loss and the supervision is excellent, if you ask any of its users or many general practitioners – and I actually agree. It’s ‘dressed up intermittent fasting’ but it works. That unfortunate lady mentioned above was not following the programme correctly and due to bingeing habits she decided to keep bingeing on water when she was fasting. It reflects a psychological state, really, and is very unfortunate. Just for the record, a loose limit for the cutoff for maximum water consumption is given in this Wikipedia article – the kidneys can only eliminate 1 litre per hour of water, on average. If you drink those sorts of amounts you are flirting with disaster. 500mls an hour is probably safe for an adult, if you really need to keep bulking the digestive system with water.
For some perspective, probably less than 10 people die due to water toxicity (in the whole world) every year. That is regarded as “negligible” by medical statisticians. None of those deaths – to date – have been linked to intermittent fasting (but do let me know if this statistic changes).
I hope this deals with any safety queries out there in relation to intermittent fasting.
Idai Makaya
www.idaimakaya.com
