If you want to lose weight, you want to be in a caloric deficit — want to eat less calories than your resting calorie burn number. Cycling/swimming an hour or so seem to be great methods of burning calories. While walking an hour too burns quite a lot of calories, cycling/swimming does more. Try low-carb but high protein diet but make sure you mix in all of the nutrients because it's needed for your body.
If you want to maintain your weight, try to eat calories just around the number of your resting calorie burn amount and that is considering you're not that physically active.
You should try out other forums — particularly made for fitness — to get a better grasp. http://www.bodybuilding.com/
is a great start. You can also have a look around YouTube — many personal trainers/regular guys have started up channels to help people like you get fit.
Once you get a good grasp of how fitness generally is, you should be able to understand how to eat healthy, even as a tactical operator. As a matter of fact, you'll learn how to eat healthy in any situation. It's sort of making a good base for yourself and branching out from there.
I hope I was able to help you, good luck!