Hi Eric (Chris)
Two possibilities occur to me
1) is he losing via measurements? How are his clothes fitting? Looser? Does he ‘look thinner’? Sometimes it’s that the fat is going from the visceral stuff round the organs, and then the weight seems to plateau whilst you’re actually getting thinner.
2) are you keeping a count of the carbs you’re eating? I know you’re following the BSD no ‘bad carbs’ i.e. no bread, flour, rice, potatoes etc., but it does seem that restricting the carbs you eat within the 800 calories can ‘jump-start’ weight loss.
If you use an app like My Fitness Pal, you can check the carbs, fat and protein within you calories. Then you can target under 50g of carbs per day (this seems to work for most people here) within what you’re eating, and that will certainly help your OH lose weight.
Apparently some people are ‘less tolerant’ to coping with carbs and changing their metabolism to burn more fat from their fat cells – so maybe you are able to cope with what you’re eating in terms of carbs, and your OH isn’t?
I know when I started this I was eating too many carbs within my veggies and was surprised to see exactly how many. It changes what you choose to eat when you have MFP telling you how many carbs there are – I decided, after looking and being astonished, that I would swerve apples and just not have any during my 8 weeks. I preferred to spend the calories on less carby things!
My OH and I are operating on 20-30g of carbs per day (you can experiment with this to see what suits you under the 50g I mentioned), and have seen very good success.
Hope this helps 🙂