The 5:2 Fast Diet: a disordered eating revolution

Every man and his intermittently fasting dog is doing the 5:2 diet at the moment.  While periodic fasting is hardly a new method of dieting, this particular form caught the public imagination in late 2012 after the airing of a BBC documentary “Eat, Fast and Live Longer”. Hosted by medical journalist Michael Mosley, and followed up by his best-selling book, the show convincingly demonstrated the many benefits of eating normally for 5 days a week and severely restricting calories for the other 2: not just weight loss, but increased longevity, reduction in susceptibility to forms of dementia such as Alzheimer’s, decreased insulin sensitivity, lowered cholesterol, the list goes on. And weight loss. Did I mention weight loss? Because let’s be honest, that’s the main attraction. The book’s a bestseller, and every second person is talking about their 5:2 journey, from Kate Langbroek to Kate Middleton’s uncle. Even Benedict Cumerbatch is on board. The appeal is pretty undeniable. You eat what you usually do for 5 days of the week, and for the other 2 you restrict your calorie intake to 500 (for women) or 600 (for men). And you lose weight. These ‘fast’ days are non-consecutive, so you can always have that biscuit tomorrow. For those who struggle to maintain a consistent healthy eating and exercise regime (ie. most people), the 5:2 diet is quite the dream discovery. After all, anyone can manage to diet 2 days a week, right? You’ll have to ditch alcohol on those days too (unless you choose to use up your 500 calories on a couple of glasses of wine), so there’s the added virtue in that. Of course, the weight loss depends on you not eating the entire fridge on your ‘non-fast’ days,  but most testimonies in the 5:2 book say the need to overcompensate fades quickly, once your body realises you’re not going to be surviving on 500 calories every day.

Looked at in this way, the 5:2 diet seems like a sustainable “way of life”. But filtered through an eating disordered perspective, it suddenly seems much more unhealthy. There has been very little medical research done on the long-term effects of the 5:2 diet, and rigorous valid studies are as yet absent. The claim that only restricting caloric intake for 24 hours at a time does not suppress metabolism is unsupported. But even if we just consider the wealth of anecdotal evidence flooding the internet, a trend of thoughts and behaviours emerges. While dieters report additional perks such as clear-headedness, increased energy and better digestion (along with easy weight loss), many like Lucy Cavendish also report dizziness, obsessive thoughts about food, irritability, tiredness, headaches, and on their ‘non-fast’ days, eating everything in sight. They advise drinking lots of water when you’re hungry, and loading up boring meals with low-calorie, high-flavour condiments such as salsa and mustard. To anyone familiar with restrictive or binge/purge eating disorders, this sounds like a roll call of warning signs. In 1944, the Minnesota Starvation Experiment took 36 men and reduced their caloric intake from 3200 to 1560 per day (more than 2.5 times what the 5:2 diet allows on fast days – but this was every day) over a period of 6 months. The men quickly developed symptoms similar to those displayed by those with eating disorders: an obsessive preoccupation with food, irritability, difficulty concentrating/sleeping, and demonstrated binge eating on re-feeding. Sound familiar?

While the 5:2 diet is touted as a sustainable health miracle, if I turned up to a therapist  and described this as my personal eating regimen, and my accompanying thoughts/feelings – but left out the 5:2 brand name - I'd most likely be told that my eating was disordered, and probably offered psychological and practical strategies to try to help correct this. This is not to say that the 5:2 diet will cause someone to develop an eating disorder (though, as the book mentions all too briefly, the diet should be avoided by those with these illnesses). But the diet does normalise thoughts, feelings and behaviours that mimic those of eating disorders. In a society already so consumed by food and weight concerns, we are edging ever closer to explicitly encouraging pathology, clothed in seductive marketing and masquerading under the name of health.