Can someone please help before my brother kills himself?

I am really worried about my brother, he is 18 years old, in with the wrong crowd and morbidly obese. He is 5'10 and nearly 17 stones. He used to smoke about 15 cigarettes a day. He's now quit but he will drink a bottle of whisky in a night without thinking about it. He eats a lot of fast food and will often bring a kebab home for tea rather than eating what our Mum provides. Admittedly none of my family are the healthiest, with me 1 of the 2 slimmest, but my brother is frighteningly big. My Dad has ped on a lot of his bad eating habits to my brother. We all like a bit of drink now and again but we'll have 1 or 2 gles, whereas my brother does a bottle. He's just had surgery on his spine and he was warned before his first operation about being at risk of cardiovascular disease. I'm writing this for his own good and mine, my brother is 1 of 2 people who truly understand me. What can I do?