My understanding is that GM food is actually pretty safe. Safer in some ways than non-GM, because it is disease resistant and does not require as much pesticide use.
GM therapies for people could overcome cancer and heart disease directly, to the point where trans fats are harmless. It takes an entire lifetime for trans fats to cause the kind of damage you are talking about. There are also healthier forms of margarine you can use now that we know about that, which actually will reduce your risk relative to butter / animal fat. (But it's still calories so if you eat a lot you will get fat and this will increase your risk.)
The main reason we have heart attacks and cancer to begin with is aging. Good luck curing that with natural approaches only. No matter what natural plants you eat, your body will slowly degrade. GM presents us with the amazing possibility of living hundreds of years. It's artificial, and that's a good thing. Nature is out to get us, and wants to kill us in our first century of life. That sucks!