If you value your health, I'd take it easy on the processed, prepared foods. That's a reliable way to health problems for the average person, and I know plenty of people who have them who eat an unusual proportion of garbage food. Bad habits usually don't show immediate results, but that doesn't mean you aren't setting off bombs inside your body that you'll eventually pay a stiff price for.
Not all natural foods are completely healthy either, but you can get by on at least a minimal amount of atrocious foods by avoiding the massive amounts of sugar, salt, and fats (including dangerous trans-fats) in prepared foods. Why are they in there? Because they taste good and sometimes act as filler too. Think they won't be in there? Ask yourself if people selling them like making money. They're in there.
By all means, cook when you can. It's almost impossible to add as much garbage to ordinary cooking, even by accident, as food companies put into their junk on purpose.