Pluot said...
Ileostomates tend to have lower Vitamin B12 and Vitamin D because of disruption to the ileum, but those can easily be supplemented.
J-pouchers aren't immune to malabsorption issues:
www.ncbi.nlm.nih.gov/pubmed/22933864@Shosh - As far as I know, there are no studies linking colectomy with weight gain, but so little still seems to be known really, e.g. what impact losing your gut flora permanently has. In j-pouch folks there seems to be some evidence that colonic bacteria eventually re-colonise the pouch, but in ileostomy folks the colonic bacteria have been made permanently homeless - there is nowhere else they can relocate to.
Everyone bangs on about
how weight gain is nothing more than 'calories in, calories out', even when science shows time after time that there are other factors besides calorie intake involved in obesity. For example, our gut flora.
www.theguardian.com/society/2016/jan/28/gut-bacteria-changed-my-life-dieting-food-blood-sugar-dietYour husband may not be doing himself any favours by cutting all carbs. Carbs have taken over from fat as the new food enemy, but as always people chuck the baby out with the bathwater when they do that kind of thing.
PS: It's worth looking into a thyroid/hormonal disorder, like nssg suggested. Certainly an uncontrolled underactive thyroid will make it nearly impossible to lose weight. However, I'm guessing your husband's doctors have done a million blood tests and considered all the obvious medical causes already.
One final consideration: you said your husband "is not good at logging his intake". Is there any chance he eats in secret when you're not around? Also, most exercise is useless for weight loss, though your husband should still keep up with the walking for health reasons - just don't expect it to contribute to weight loss.