I've been trying 5:2 since the start of January. Not lost much yet but DH didn't in the first few weeks and he's now lost 2.5 stone over 8m so I know it can be slow to start.
Anyway, I've consistently found that I get pretty emergency type diarrhoea (sorry tmi) about an hour after eating breakfast on the day after a fast day. Just muesli, nothing new. Even had it after just having a banana to break fast.
Google tells me this is not uncommon? But does anyone have experience of this and then have it settle after a few weeks? Any tips?
Otherwise I'm going to give it another week and then give up. Can't go to work in the mornings and have to run to the loo!
Apologies in advance if I don't get back quickly, I'm running round after a 3.5yo and 9mo...
I've had a few similar incidences OP. What helps is skipping breakfast or at least pushing it back as far as I can then keeping it simple (I can no longer eat muesli as it's too hard on my tummy in the morning). If I need breakfast then fullfat natural plain bio-yoghurt (full of natural probiotics which line the tummy) and half a banana mid-morning around 11 really helps (then I push lunch back to 2pm).
I've read that one should break the fast with a small amount of protein and veg, also that some folk react badly to fruit / juice / sugary cereals / fizzy drinks / bread when empty. However, stomachs vary so much:
Regularly after a Saturday FD, I skip Sunday breakfast and do fasted spin instead, followed by a protein shake. So, my first real meal after 35-45 hr on max 700 cals is a very late 2000+ cal Sunday lunch, e.g. pizza, fries, salad, ice cream and pancakes. Then I just have a small soup for supper. I've never had any stomach problem on 5:2