It's actually rather easy to eat healthy at a fast food restaurant, if you know what to eat. And no it's not the veggie sandwiches at Subway or even some sad skinless chicken breast. What you need to do is simply avoid sugar and carbohydrates, that's it. As long as you do this and keep your calorie count to a reasonable level (1800 to 3000 depending on your size, age, gender and activity level) and avoid the carbs and sugar you can eat fast food without worry. Some folks will tell you that the sodium levels are too high in processed food, they're wrong. Study after study has show that sodium does NOT cause high blood pressure or heart decease, and it will cause problems for those who already have these risks a whopping 2% of the time. Other will tell you that the fat content is too high, these folks are also wrong. Saturated fats (animal fat) does NOT make you fat, or cause diabetes. People are pointing at Paula Dean as proof that butter and fat are unhealthy because she has diabetes, of course they blame the butter and fat in her cooking while ignoring all the sugar and flour (carbs spike your blood sugar) and of course diabetes is a problem processing SUGAR not fat.
If you'd like to learn about which food's are actually unhealthy and which foods are good for you, you should watch the film Fat Head.