To achieve 6 pack one must go through 3 tests:

- psychological: why do you want 6 pack?

- genetical: if you accumulate most fat around the midsection, chances are that you need to be extremely lean to see the definition of ab muscle. Such extreme leanness may be damaging to your physical and mental health...

- technical knowledge: most people do crunches for flat belly thinking that this is how you burn fat there. At best one will also start "watching their diet" avoiding bad foods. This is a lottery: you may put inhuman willpower into not eating sweets and cake, but you never know whether this place you into calorie deficit or not. A calorie deficit is a single and compulsory condition for burning fat.