Honestly, it is very hard to say-considering that I don't know exactly what he has been eating, how much, if any, activity he is doing, and all of the other variables.
I do know, that weight loss takes time. Very obese people usually DO lose a lot in the first week-but this is not fat loss. It is usually water weight from their normally "bad" diets.
I would recommend patience, first off. Losing 1/2-2 pounds a week is a healthy weight range. If he has lost a pound in two weeks, then he is on track with that.
He did not get to 400 pounds overnight, and he isn't going to lose it overnight, either. Patience. Even if he only loses 2-3 pounds a month-which, I think if he is REALLY staying on plan, he will lose more-then still, that is 24-36 pounds in a year. That would be wonderful for his health.
In the meantime-here are some suggestions:
~WW goes by a Points system, but the better the food he eats, the better his results will be. Meaning, just because it is 1 or 2 points, doesn't mean it is good for him. Make better eating choices when possible.
~Stay in the points range allowed daily for best results.
~At his weight, strenuous exercise may be too difficult-but he needs to do SOMETHING, especially if he is a diabetic. Start with a very short walk. It may be just down the road 4 or 5 houses and back...but do SOMETHING. Over time, when he has lost a few pounds, it will get easier, and he will slowly be able to do more.
~He should keep a food journal when he keeps track of his points. Don't just write the points and add them all day. Write next to the points what the foods WERE. This way, he can look at it, and see if he hasn't had any fruit, or any vegetables, or if he has had more than one serving of "junk" today. If he can see the overall picture, it makes making better choices a bit easier.
Let me know how he is doing, please.