It can all get very scientific about what to eat, how to gain mass, how to cut weight and lean up while minimizing muscle loss. Go jump on a body building forum and have a look. Body building is too ego centric and too much of a full time job for me to have any interest in it.
The maths is simple though. If you want to lose weight its as simple as calories in being less than calories burnt. The opposite is true if you want to gain weight. Muscle is built by using them and causing them to react and adapt to being used.
I don't think that is the point of this thread though. This isn't so much about losing weight, retaining muscle, buffing up etc, but more about improving health and lifestyle, which is exactly what I aim to achieve in life. Its about applying some common sense to eating. Knowing what you can eat a lot of, and what to have in moderation. While I'd never go full paleo as I love to have breads, pastas, noodles, rices, etc, they are never the bulk element of a meal. I also shy away from most processed/premade meals and will cook from scratch where possible. A typical meal includes some meat (fish, chicken, beef, pork or lamb). A large side of salad or veg (usually just dressed with some olive oil and salt/vingearette - home made), and then depending on what it is it may have some carbs. Say a stirfry is all veg, some meat and a small amount of rice or noodles just to soak the flavours up. Lunch will be a large salad roll. The roll is just to hold the meat and salad together for me.
Softdrink and alcohol. That big ol polar bear!! Thats where my good work comes undone more than anywhere else. That and beers. If I could cut them out I'd probably weigh 10kg less. But meh.. I'm happy!