It's not a popular sentiment to say this, but you can out train your diet. People have done it for thousands of years and people do it today. I have done it and I have seen hundreds of other people do it. It's just not popular to say that if you are selling a nutrition program, idea or fitness lifestyle.
The problem with out-training diet is most just can't train that hard because time, dedication and work ethic are things people don't have. People have jobs and other hobbies/parts of their life that are more important than training. There is no shame in that - you can still be very successful (insanely) and not dedictate EVERY moment of your life to training. But it is possible to out train your diet. What do you have to do? Your body decides. There is no one perfect training and conditioning schedule.
There are two things you CAN'T out train - your past and your age.
If you grow up fat and never learned how to eat correctly, you can't out train that without a proper diet. This is a good reason to teach your children GOOD (not seeking perfection) eating habits at a young age. They won't have to suffer from a life time of self-esteem issues, relationship issues, a hampered social life in high school and really, being an all-around drama king/queen about their body. If you are 18 years old and you don't know what healthy foods are and what they aren't, you need to educate yourself. If you are old enough to vote, you are old enough to take 100% responsibility for what you shove in your mouth.
Age is another thing that is impossible to out train without a healthy diet. Eating like a slob will catch up to you eventually - either in the waist or in the doctor's office. Not to mention joint pain, stomach problems, reflux, etc. At a certain point, you should eat like a grown up. Yes there are exceptions to these rules, but using them to prove your point only proves the biggest one of all.