Protein Shakes - meal replacements

[Neitheronethingortheother]

Hi I have been doing the 5:2 diet for the last few months. Not really losing much weight as i seem to over compensate at the weekends for havnig had 2 fast days during the week. I am going on hols in 4 weeks and need to drop some weight if I am going to feel at all comfortable. Went to the shops to buy some clothese this morning and instead ended up buying tub of protein and some supplements. Is it ok to have a protein shake and then my dinner on a fast day? There is 109 cal in a scoop and I had half a scoop with 300ml of skimmed milk. So do I just add up the calories and take it from 500? Does this go against any of the ethos of the diet?

Please don't.
Meal replacements are NOT the answer.

You need to get your "normal" eating within the healthy range.
What is your TDEE?
How close to it are you keeping on non fast days?

If you do 4:3 and 16:8 and make sure that you stay within your TDEE on the 4 days, you'll shift the weight
AND start to build healthy eating habits.

Supplements are not food. THey are a marketing job

I take protein shakes as a meal supplement, not replacement, and only after lifting weights.