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Friday, 17 August 2012

The 5:2 Diet? Good, Bad or Mad?

Laura and Miriam asked me to comment about the Intermittent Fasting or 5:2 diet which has been attracting rave reviews on the “inter-web”.

Scientists have long known about some of the benefits of fasting for longevity. Fasting reduces levels of hormones like IGF1 (insulin growth factor), implicated in accelerated ageing and age-related diseases like cancer and diabetes. It also seems important to reduce your protein intake, so calorie reduction can’t be attained by eating lots of protein – a la Dukan.

Scientists at the University of Illinois have trialled a variant of continual fasting, which they describe as Intermittent Fasting. In an 8 week programme,  people eat fewer than 600 calories on 2 days a week with eating what you like on the other 5 days. They have claimed that it improves IGF and other ageing markers as well as enabling weight loss. Here I insert a warning, this trial was only for 8 weeks and we don’t know what happens in the long term.

There is a Fasting For Longevity movement in the USA. Members have been studied extensively. While they claim to have no issues with weight and eating, most show similar personality characteristics to people with anorexia and they display all the signs of people with classical eating disorders, preoccupation with food, cravings and high levels of emotional distress.

The 5:2 way of eating intended for longevity has been captured by the weight loss movement. Now there's a surprise!   For weight loss, this isn’t new. In the 1980’s it was deemed useful to eat sparingly during the week and eat everything you like at the weekend. Many people lost weight on this regime and then- hey - they put it all back on again. Feasting and fasting isn’t the good idea that it is supposed to be.

Behind the hype, even the BBC admits that current medical opinion is ambivalent about the benefits of fasting. Psychological opinion concurs. Fasting and feasting drives people into polarized thinking, good and bad day mentality and catastrophic reactions when dietary rules are breached. Apart for providing fodder for the pro- anorexia movement or the orthorexic community, this insensitive publicity may lead people to thinking that they are doing something that they should be proud of, when they may be doing something which isn’t really very good for them at all.

Let’s take some of the research which was NOT given head space by Michael Molesey and his team. A number of robust studies show that after one month on intermittent feeding, experimental aniamals show a series of behaviours similar to the effects of drugs of abuse. They begin bingeing, and during fasting periods there are withdrawal signs indicated by signs of anxiety and behavioural depression together with enhanced longing for sugar.

Brain imaging shows gross and complex changes in opioid systems such as decreased enkephalin expression in the appetitive system in the nucleus accumbens, with reduced dopamine levels (reward chemicals) and increased acetylcholine (stimulating appetite). The net effect is the creation of sugar dependency together with cross sensitising to other drugs of abuse.

Feasting and fasting thus risks bringing forth long term problems with control of food together with the emergence of compulsive behaviours and emotional problems too.

So with humans as with rats and other primates, it’s useless to test one set of behaviours in a vacuum for 8 weeks and present it as a panacea for weight and other issues. Mr Mosely may have felt good on this diet, but it's pointless for the millions of people out there who have eating disorders and for who this diet could make things considerably worse. I have given this issue lots of head space and I conclude that programmes like this are unbalanced and risk creating false hope for anxious people who are trapped in a poor relationship with food. As the man said, “fasting, like eating, is best done in moderation”

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