Hi, Charley Webb

Firstly, congratulations on 3kg loss in 3 weeks if I read your post correctly. That is a very significant result and if you think it is less than you hoped I think you might be expecting too much as those 3 kgs didn’t go on as excess weight in just weeks and this whole weight loss thing is not an exact science and rarely follows the straight and narrow.
For your husband I have much sympathy,starting with you and eating the same as you (offering each other moral support etc) and not losing anything after 3 weeks I would not be losing motivation but probably have already lost it.
All is not lost. There is a risk that you are not comparing like with like in that your husband is a very different set of circumstances. The fact that he is eating the same as you and the reduced input is not making any difference on the scales means looking elsewhere and searching for the glitch and maybe trying some additional things before giving up.

My observations would be to set small weight loss goals to start with and not anything similar to you (who is clearly in the elite ‘weight race runners’ group.) What is happening on non fast days would be the next thing, anything taken to compensate for fast days that he is not consciously aware of.(Brain plays great tricks on us sometimes).
He also might like to take something out of his normal diet on the 5 non fast days that is a a hidden demon and have it as a rarer treat.For example, I found that the favourite frozen pizza (always stocked in the freezer) I had once per week was over 700 calories a pop I decided it was going on the very occasional list….(awareness of what I was taking in non fast days became the watchword)
As long as his fast days are not too painful he might extend to 4:3 for a week or two just to kick start that pesky number dropping.
Does he have the opportunity to increase his weekly activity/exercise levels in anyway, something easy to do and sustainable.
From a mental perspective it might also be a question of managing expectations and try and take the longer term view, that for him this is not a quick fix with instant results,like yours, and that a more relaxed outlook with the view to persist for a few months with it might just be the the way to get past this motivation roadblock.
Obviously, he will have ruled out any medical reasons for the stubbornness in weight loss and the best advice at this point (if all the above considered) is to just give it a bit more time and stick with the programme. If he has time read the FAQ on this forum, some good answers in there.

Finally, from my personal perspective I was very skeptical of the 5:2 when I started,having struggled for years with weight gain and all its consequences. I tried 5:2 over a year ago but gave up quickly as I did not follow the concept seriously and see any results. I started again the end of January 2015 and have lost 13kgs, reached my goal,but more importantly my health issues and general fitness have all improved dramatically.

‘Keep on Keeping on’ as they say and it will come.
Good Luck

J Cato