Hey Kitana, I used to work with a guy and still do once in a while that fits your husbands desciption almost exactly, this guy is now in his late 30's and still has this problem. Same weight and height. First, no workout in the world will change his metabolism. It can only be done thru diet. The best I could do was about 15 pounds. Assuming that he is eating at least 5 good meals per day at around 1k each ( I know you said 7k) then have him add this drink to his diet. He will need to sip this between meals. Try and drink the whole thing thru out the day. DO NOT drink it all at once! Tell him to take his time and sip it over a period of say 15 min. He can break it down into 3 in between meals if he likes. More if he needs to. He can add flavoring or a banana to it or some kind of sweetner like sucralose.
2 quarts half & half
12 whole eggs
Scoop of choc. whey (optional)
flavoring and or sweetner
Since I don't know his diet all I will add is that he should be eating good food, not junk or foods loaded with sugar. Good luck.