Hormones, sleep habits and insulin sensitivity play a huge role, the examples you gave are the sharp ends of the spectrum, most people fall in to a middle ground where years of bad habits accumilate
Absolutely. Diet is not just food, but your whole life's regime and activity. Eating the wrong foods, and not doing the right things affects your hormonal balances.
Those that "don't get fat" or "get fat" in most cases are just not eating enough or too much vs what their bodies can cope with and what their lifestyle dictates.
No way is that study right nowadays.
I'm wary of it too. However I will say that carbs before bed aren't really a problem sure, but purely on how your body works the insulin responses you get from carbs before bed aren't so good - certainly if you're keen on optimising and maximising the effect from the GH releases when you fall asleep you're just taxing your body for the wrong reasons. You are far more likely to store fat with lots of carbs at night that you are with high protein and fibre at night.
Most people stay thin or fat not for what they do, but for what they don't do.
A bowl of cereal is NOT breakfast. Cereals are part of a breakfast maybe.
Another thing that you're going to struggle with as a vegetarian is getting the right nutrition. There are a handful of big bodybuilders, who are veggie, but they have to supplement the hell out of their diets because they just will not be getting the nutrition into their bodies naturally. To get enough nutrients in they have to supplement - you have a rather limited amount of choice for protien and iron as well as creatine intake through a veggie diet (just to name 3 basic nutrients).
The reasons why the Roman and Greek armies were so feared and why they were so powerful (and remember, look at the Greek and Roman statues, they were chiselled figures of men (pun intended)), is because they had rich protein and fatty diets full of meat and fish, (nuts and berries too). So they were leaner, stronger and more resilient than the rest of their succumbing nations. It's just a small historical article and example that I read about - a small extract of a big history book, but one of the things they focused on were the diets of those people.
We were designed to eat protein and fats - carbs as well, but as a filler, not a constituent part of the diet. Our bodies still haven't adapted to the processed crap we shove down our throats - most carbs we buy are processed to a certain extent. That's just a fact of modern life. I still buy and eat them but I make a conscious effort to avoid them if I can.
Diet takes a LOT of effort, discipline and time to get right. You're going to have to put a LOT of effort in - it's not easy but if you want help we're happy to help.