IUPS 2013: Are you on the 5:2 diet?

The 5:2 diet has made the leap from the eccentric circles of celebrities to mainstream public adoption,  and has many supporters who claim the approach can be applied to other areas of life ( e.g. Worry, TV watching, alcohol, shopping). Its popularity stems from the fact that conventional restrictive diets are highly demotivating; eventually the subject tires of the tedium and calorie counting, gives up (possibly in a spectacular fashion) and returns quickly to  their pre-diet state or worse. In the 5:2 method, a limited diet is only imposed on two non- consecutive days of the week; on the other days, the subject is free to eat as they choose. The 'fast days' are fairly severe as intake is restricted to around 25% of the user's energy requirements - approximately 500 calories. This would be punitive over the long term but the key factor here is that the participant knows that they will be able to eat their normal diet the next day and so perseveres. The popularity of the 5:2 diet is such that it could be described as one of the largest unmonitored public experiments.

But does it work?

A considerable audience gathered to hear Dr Krista Varady's lecture 'Alternate day fasting: a novel dietary restriction regimen for weight loss in humans' which described the results of a pilot trial in the USA. In this study, 20 obese makes and females took on a regime where, for three days a week, dietary intake was limited to 25 % of their needs. This was imposed over 8 weeks: for the first 4 week block, the patients were 'control fed' (as it wasn't thought that they would be able to calculate a 500 calorie meal themselves) and for the second half of the trial, they prepared the 'fast day' meals themselves, using dietary advice. I was impressed by what a 500 calorie meal amounted to - a vegetarian pizza, an apple and a handful of peanuts. I would struggle to eat that over a two hour period, which the participants were required to do. Then again, if it was the only meal you had that day...
Only four participants dropped out of the study and at a fairly early stage. The remainder lost an average of 5.6 kg with the rate of weight loss being fairly steady throughout. Nevertheless, in traditional dieting regimes ( especially those involving no additional exercise) this weight loss is usually lean muscle,  rather than fat, which reduces the amount of metabolically active tissue, making it even harder to loose weight.  In THIS case, however, about 90-95 % of the loss was attributable to fat. The subjects also lost about 4cm of their waistline, lowered their systolic blood pressure by 6 mmHg and reduced their LDL cholesterol levels by 20-25%. Subject compliance, as assessed through  feeding diaries, was 87%.

But what was happening on the 'feed days'? One would presume that there would be a temptation to binge...similar to the pancake syndrome before lent. These participants, however, were found to only consume 110% of their energy needs and so didn't make up the deficit. Many of them were even happy to carry on the diet with Varady stating that 'after the initial two weeks most have no problem with the fast days'. Some of the audience were sceptical about the long term effects and Varady admitted that the rate of weight loss did seem to drop after 24 weeks. Perhaps this is only to be expected though- one can't keep going down forever. The most striking thing to me was Varady's self-confidence in  the technique 'I do this a couple of times a year after holidays to shed a few pounds'.

Are you on the 5:2 diet? Do you apply it to anything else? Please comment below!