There are some good links in the new sticky that came out yesterday, I'd read up.
As far as calories go, our bodies all expend a specific number of calories based on our weight/activity levels/body-makeup daily. It has always been a thought that a lb. of fat is 3500calories, meaning, if you want to lose a pound, you need to expend 3500 more calories than you consume. This is not my contention mind you, but it is a widely accepted theory. Ergo, if you expend 500 calories more a day than you consume you lose a pound a week, which is a healthy amount. Your body, currently, might be expending 2000 calories a day just running itself, this doesn't even take into account working out or even just moving around. Having 1200 calories a day leaves way too big a deficit, and could place your body in "starvation mode". In this mode your body shuts down a bit, and starts storing fat instead of expending it. Fat is very important to your body's health due to it's function of protecting major/vital organs. So, you should consume more calories spread nicely throughout the day. 3 meals with 3 snacks should do with your biggest meal (calorie-wise) being breakfast. A spread like
500
200--snack
400
200--snack
300
200-snack
gets you 1800 calories and keeps your body working hard through out the day to burn off the constant stream of calories.
Now onto PWO nutrition
Post-workout nutrition and it's timing is key to recovery, muscle growth, and, weight loss. Your body has been broken down during your workout, and now it's ready to accept all sorts or nutrients into your system. While the tuna isn't a bad choice, it by itself, certainly is insufficient.
The first thing you'll need post-work out is carbohydrates (omg carbs
) along with protein to help facilitate some key triggers in your body. The best post-workout nutrition would be in a liquid form, i.e. a protein shake because it's broken down faster by your body. However, most-to-all shakes do not have enough carbohydrates in them. You are looking for 2g of carbohydrates for every 1g of protein. There are many sites that will tell you the exact # of grams for your weight/goals but for me, a 155lb male (what is that, like 70kg I think) I take in 70g of carbs and 35g of protein post workout. You can also add supplements in powder form to the shake like BCAA's, L-glutamine, etc... You can research these supplements to find out more on them.
Finally, timing is extremely important, there is a smallish window of time (say 45 minutes) after your workout where it is paramount that you consume this nutrition, and the sooner, the better.
Hope this helps, check out the sticky for some good links.