There’s a pretty common saying that goes something like this: “Everyone has a six pack, for most of us it’s just covered up.” It’s absolutely true. A six pack is simply your abdominal muscles (rectus abdominus) below a layer of skin and body fat. You can change the size and strength of your abdominal muscles by completing various core exercises such as crunches, leg lifts, medicine ball work, and the like, but if you still have a high body-fat percentage, you won’t be able to see them, no matter how well developed they are. Which brings us to another point core stability and functional strength outrank six-pack abs any day of the week. If you’re going to do the work anyway, do it for a good reason and incorporate exercises that develop your entire torso, not just your six pack.
If you’re dead set on achieving a six pack, the only way to it is to lose a considerable amount of body fat, and that CANNOT be done, to a significant degree or in a healthy manner, in one week. Not only that, you can’t choose where the fat you’re burning is coming from, so you can’t exercise specifically to lose belly fat. By changing your diet and increasing the amount of aerobic activity you do, it’s safe and possible to lose one to two pounds of body fat per week. For some people, it may only take a few pounds of weight loss to begin seeing a six pack. On the other hand, there are people who may have better-developed abdominal muscles, and greater core strength, yet won’t be able to see a six pack for quite a while.
In order to lose body fat, your daily caloric intake should be roughly 500 calories less than your caloric expenditure. Just realize that a bigger deficit is not going to get faster results. A 1,000 calorie deficit may, in fact, cause you to store MORE fat and put you farther from your six-pack goal.