Well, there are some select individuals that can eat whatever they want because their metabolism is always in overdrive. Unfortunately, the majority of us, especially as we get older, have to eat a cleaner diet in order for those abs to start to show.
We all have abs-
Everybody's genetic makeup is different. Some people will have a six pack, others can even have an 8pack. Some people have big ab muscles, and others have small ones. But, you will never know which type you have if it is covered with fat.
How do you make your abs really show-
There are two things you need to do in order to make your abs really show. One make your ab muscles bigger. Two, get rid of the fat that is covering them up. Once the fat is gone then it is only a matter of definition. This is where doing all of those sets of abs finally pays off. However, if you have too much fat covering your abs, then it doesn't matter how many sets you do because though you are making your abs stronger, you are not making them more visible.
This is where cardio comes in. Cardio is how you burn all of that stubborn fat. High intensity cardio mixed with weights or calisthenics is your best bet. You can look at a track runners body as a perfect example. You will rarely see a track athlete that doesn't have a pretty nice stomach.
Don't kill your hard work with Junk food-
Empty calories are not your friend. Sodas, chips, candy, and white food (rice, pastas, flour, bread etc..) all work against your midsection. Choose healthy alternatives such as : fruits, veggies, water, nuts, etc...