After a workout you want to eat 2 things: Protein and carbs.
Protein (Which builds muscle.) Tuna fish, egg white and chicken are great sources of protein... BUT, they are whole foods. Whole foods digest slowly and you want something FAST. Whey protein is your best option. And you should have it in liquid form. (which will digest even faster!) So... a protein shake is your best option for an 'after workout meal'. And you want to have it ASAP. Shoot for 30 min to 1 hr after your workout.
The next thing you'll want are carbs. Carbs will be used by your body to restore muscle glycogen. If your post workout meal doesn't contain carbs, your body may actually instead break down muscle tissue for this same purpose. That would be a bad thing. Carbs also create an insulin spike which helps to move nutrients into your muscle tissue quicker.
You don't want 'good carbs' like wheat bread or brown rice because they have fiber (slows digestion) Something like a baked potato would be a better choice. But, again, that is a whole food. If you really want to go extreme, you will want dextrose (which is a form of sugar) I'm not saying to eat cookies!! Dextrose can be found in powder form and mixed into your protein drink. (there may even be drinks out there that already have it. ??) You can buy low-cal protein drinks that are better for women. We are looking for the nutrients but not the calories. (unlike guys who want more cals for bulking up.)
The one thing you DO NOT want after a work out is fat. Fats can be good... and we definitely need them in our diet. But fats slow down digestion and will counter the benefits of eating protein and carbs after a work out.
So what about before?
In general, the closer you get to your workout start time, the fewer calories you should eat. The nutrients that make up those calories should also shift. It takes the body four to six hours to digest fat, about three hours to digest protein and about two hours to digest carbohydrates.
So, here are a few rules of thumb to follow:
*If your workout is four hours away, eat a regular meal that combines protein, fat and carbohydrates, then have a small carbohydrate-rich snack closer to your exercise session to tide you over.
*Three hours before working out, make it a smaller meal and lighten up a bit on the protein and fat.
*Thirty to 90 minutes before exercise, have a snack of easily digested carbohydrates
*If you only have 15 minutes, go for a sports drink or a few Saltines.
The science of nutrition can really play a big role in fitness, weightloss and sculpting your ideal body. But, you have to do what works for you! Someone asked me this question... I thought it was great and I figured others may want to know the answers too!