Moogie wrote: What a great idea for a topic!
I've been doing 5:2 since August, I started on lunch & dinner of 250cals but this made me extra hungry so after 6-8 weeks doing that I swapped onto a 400-500 cal dinner, sometimes allowing myself 50 cals of that to have a low cal soup or hot choc during the day if needed. I fast on Mondays & Thursdays. I try not to eat after dinner on the day before a fast day, but that isn't always adhered to

The only side effects I've had have been:
Feeling cold Worse since now it's winter, and moreso too when it's 'that time of the month'.
Irritable/snappy Definately less patient with my husband when he gets home from work an hour or two before dinner! I work from home all day so am on my own and don't know if I'd be snappy the rest of the time too. I don't seem to get snappy with anyone else I encounter in the daytime - delivery folks or people in the local shop.
Loss of concentration For most of the day I feel really alert and quite chipper! About 4pm I notice a slight decline in my concentration, but perk up again within an hour and can happy carry on through until dinner at about 6.30pm. Actually this might not be specific to fast days, I'm probably just more aware of it then due to the hightened alertness for the rest of the day. I think a lot of us start to wain towards the end of work anyway!
Overcompensate on confectionary on feed days Same as above, I've found myself overcompensating in the last month but only the day immediately after the fast (Tues/Fridays). The other days I eat pretty normally. I know I'm more inclined towards snacking in cold weather and usually a chilly piece of fruit doesn't cut it for me then, I just want some comfort food! I think I'd be just as bad fasting or not

Do we also have a thread for positive side effects? If there isn, I'll go reply now. If not, I shall make one!