new question on interval training

[Guest guest]

My DH is very thin (probably a little too thin but he's naturally that way too, he used to be a long distance runner and he is still built that way). He's 46 and wants to get more fit and doesn't have much time to work out so we thought interval training would help him get cardiovascular in more easily. Most of the articles I printed out for him (thanks Kassia!) said interval training was a great way to burn fat but he definitely doesn't want to burn fat and was concerned if he did interval training he'd lose more weight. He already eats pretty healthy portions (of healthy food, maybe I should cook more stuff with higher fat content, LOL) and snacks and really isn't hungry to add more food. Should he do intervals or maybe just do them once a week rather than more often? Any thoughts or other articles would be welcome! Thank you!