hey pumpkin.. as far as i know if youve been 100 percent and each day had all shakes and around 3.5litres of water and nothing else apart fromblack coffee or tea then he is definitely in ketosis.
Make sure he isnt having things like chewing gum,,lempsips or anything that has sugar in it,, and no pepper chilli flakes etc,, all of which could be having an effect on him. However if he is ten stone and 5.6ft then his losses will be slower as he wont have much to lose........
just out of curiosity how much does he want to lose as 10stone and 5.6ft for a guy is quite light and im sure its within healthy bmi??? x