Before stating any side effects it’s worth providing a bit of detail on what IF entails for you. As you can see from my profile details on the left I have been IFing since late august last year. I 5:2 and throw in the odd day where I refrain from eating anything between b’fast and dinner. After 10 weeks or so I changed my fast days into pure fasting so ate nothing from b’fast thru till b’fast the next day. On most fast days I manage to get in an hour of road cycling or swimming and exercise regularly on non fast days too.
My list of negative side effects/experiences are:
Feeling cold Not surprisingly the winter has really exacerbated this and I now no longer fast for a full 24hrs on fast days, instead have a couple of bowls of veg soup in the evening to help combat the cold.
Irritable/snappy Experience this sometimes on the evening of a fast day.
Cramp Have experienced this some nights after fasting and exercising. Can remedy by eating a little table salt, if I remember.
Dizziness Have experienced this a few times this side of xmas, when standing up after sitting. I presume it’s linked to low blood pressure.
Decline in enjoyment of exercise Many people say that they have no problem exercising with fasting. Not so for me, I find it noticeably harder, but still doable. Over xmas I ate normally (excessively) for 10 days and noticed a real positive difference in the way I felt when exercising both on longish bike rides and when doing sprints in the pool.
Overcompensate on confectionary on feed days I don’t keep a food diary of what I consume but my feeling is that I over compensate on choc, biscuits, ice cream on feed days. This may also be more noticeable now that we are in the middle of winter, so SAD influence creeps in?
Increased bilirubin count My bilirubin count has always been high, circa 30umol/L. After 10 weeks or so of IF and after fasting for 24 hrs I had a blood test and bilirubin count clocked in at 77umol/L. This has no perceivable effect on my everyday living but I think is an interesting observation.
I hope this all doesn't read as being too negative. I still believe that it's worth continuing with 5:2ing.