Why do foreigners have such big noses? Why are Japanese people so skinny? There are fundamental differences between Japanese people and foreigners that no one can explain. But we can speculate:
Why do foreigners have such long noses? Our big noses reflect our custom to blow our nose whenever needed, even in public. As opposed to the Japanese custom to inhale in sniffles to keep "it" in while in public, perhaps the exhale and blowing of the nose, and the consequent pulling on it, stretches the nose, making it longer.
Why are Japanese people so skinny? Many foreigners can't even find clothes big enough to fit them in Japan. Even though the Japanese are getting taller, they're still incredibly slim. Japanese girls have tiny waists and you can often see men's pelvic bones jutting out. "It must be in the genes," I often hear Westerners say. I think it's more basic than that. There is a good reason there are no "plus size" stores in Japan: Size control. By only having small sizes available, Japanese people cannot get fat. They have to stay slim or go naked.