5:2 diet – to fast or not to fast?

Unlike many fad diets the evidence base for the 5:2 diet is clinically grounded, and it is effective at improving health makers and aiding weight-loss. My issues with it are lifestyle based: 

  • Restriction days will give you an energy slump, so athletic performance, concentration, energy levels etc can all be impaired so for many people it is impossible to follow because they have to work.
  • Calorie restriction will also mean hunger and likely grumpiness to go with it.
  • Some people binge on the non-restricted days and become more likely to make unhealthy choices
  • It is really hard to stick to this kind of regime long-term, so people tend to give up and lose all the benefits. This is the main reason why most ‘diets’ fail and lead people into a yo-yoing situation which can make weight-loss much more difficult in the long-run.

Whilst suitable as a therapeutic diet for certain conditions however you would struggle with energy requirements on your low cal days and fasting in general has many health benefits… its a question of when to do it, how to sustain it and getting some support while you do it.


  • Get some health diet principles in place that you can follow for life (ask me how)
  • Follow them MOST of the time
  • Do consider fasting periodically in an environment where you can be supported e.g. 1 day at the weekend when you can ‘chill’, going to a health spa.
  • Even an overnight fast (12 hours) has been shown to be beneficial so if you have breakfast at 7.30 am DON’T eat after 7.30 pm the night before.