Heart disease is caused by the build-up of deposits of cholesterol on artery walls. But that is the only blood carrying items that can be blocked by dietary intake of too high fats, proteins, and carbs. This can block smaller blood supplies that go into your spine, as well as your penis (and a clitoris) thus being overweight is also a risk for back disc problems and ed, and/or reduced sexual drive.
The key to losing weight long term is to change your lifestyle to one that you can live with. Just doing a diet never works as you can see in the results of many who participated in the Biggest Loser television show.
Suggestions. Reduce dramatically, if possible to zero, the intake of processed food. Frozen meals, snack foods, any kind of chips.... cut them all out as soon as possible. Replace those foods with whole plant foods. whole grain breads, rice, beans, potatoes (not fried, but baked, roasted) and fruits and vegetables. Any and all fruits, any and all vegetables.
Limit your whole animal products, get rid of dairy, no more than one egg a day, and stick with lean cuts of flesh.
Work with seasoning, and spices for the whole foods to give flavor to a thing that might otherwise be very unfavorable (i.e. rice, tofu).
Use a tool like cronometer.com to track what he eats for 1 or 2 days to find out how many calories he is eating today. Weigh in on a Friday morning, then cut 250kcal from your daily intake per day and track it for a week. then weigh in on the following Friday and see if you lost any weight. If not, cut another 250kcal and go for another week. Keep cutting until you are losing a good 1-2lbs per week.
It's very possible he may lose weight much faster once you start eating more whole foods because packaged and processed foods are much more caloric dense. By eating whole foods he'll likely be cutting a lot of calories out but not feeling hungry. I bet he would be shocked at how many calories if he tracks what he eats each day for a week.
https://www.ncbi.nlm.nih.gov/pubmed/9647967