Recently I’ve been seeing an increased number of clients who follow some form of time-restricted eating.  For ages the 5/2 diet was in vogue but now the 8-hour feeding window (i.e. fasting for 16 hours) is really gaining popularity.  People are coming to me whilst diligently following these regimes, mainly for weight lost; they have become totally “wedded” to fasting and often they are seeking my “buy-in”.  This has got me thinking that I should share my thoughts – probably a longer dialogue than you’ve got time for so here’s the skinny!

There’s nothing new about fasting; Ayurvedic practitioners were using it thousands of years ago and it is an integral part of many different faith traditions, suggesting there’s a universally accepted benefit – interestingly, way back then there was no differentiation between the health of the mind, body and spirit!  And proponents of alternate-day fasting claim this is how our cave-ancestors remained lean!  (Although I suspect the truth is different; instead of arbitrary and rigid feeding windows they had food supply uncertainty and, furthermore, did a lot of running around to catch it!)

Fasting for Weight Loss

Weight loss is the primary reason for fasting amongst the clients I see and, whilst obesity is clearly a health risk, I see weight loss as distinct from health benefits, primarily because so many weight loss programmes actually endanger good health!  However you want to “dress it up”, fasting is calorie restriction within a particular time period.  Calorie restriction often works well for individuals who’ve not tried dieting before and so intermittent fasting can be a good option for anyone trying to kick-start weight loss for the first time.  But, the majority of weight-loss clients I see have spent much of their adult lives dieting, which has slowed their metabolism, caused them to lose lean muscle mass, disrupted their blood sugar balance, led to episodes of “binge” eating and left them feeling reliant on some form of restricted eating to control their weight.  Plus, long-term calorie restriction can cause ongoing muscle loss, affect mental wellbeing, contribute to physiological stress and lead to nutrient deficiencies.

So rather than endorsing an approach that risks further health deterioration, I’d rather tackle the underlying causes and offer strategies to re-balance blood sugar, rev up metabolism and address suspected deficiencies.  Whilst meal timings are extremely important I believe that healthy weight loss requires taking care with what you eat and how much, as well as what macro-nutrients you are combining.

Fasting for Health Benefits

So what about intermittent fasting for health benefits?  Some research suggests that fasting can fight cancer, reverse *Metabolic Syndrome and slow Alzheimer’s disease.  Many studies have been carried out on mice/rats so more human research is clearly required but many scientists are confident that prolonged periods of time without food stimulates the body to repair itself by targeting damaged cells and then eating them for fuel, a process known as autophagy.  Cells naturally get damaged and die so this cleaning up process sounds appealing.  The bad news is that you need to completely starve for a minimum of 48 hours before autophagy “kicks in” and even a small amount of food will halt the process.  Alternatively, you could try the “Fast Mimicking” diet, pioneered by Valter Longo, but this is very specific and definitely not easy to replicate without help and supervision.


In a nutshell, I can see there is a place for intermittent fasting and the potential health benefits sound exciting.  But when it comes to fasting for weight loss it would not usually be my first option and, if used at all, it should be a short-term strategy and not become a way of life.  Furthermore, no different to managing any other health concern, lifestyle and dietary interventions will be most successful when they are completely personalised.

*Metabolic syndrome is a collection of health risk factors that include central adiposity, insulin resistance, hypertension and high cholesterol. This cluster of risk factors is linked to an increased risk of developing type 2 diabetes and cardiovascular disease.