Why are you seeing increasingly more round-faced, plump people on Chinese streets? People with a predominantly high-carbohydrate diet are not necessarily wealthy; but when you see someone with a well-proportioned physique, defined lines, and clearly consuming large amounts of quality protein, it often indicates they have better economic conditions. Because in most countries around the world, lower-income populations typically have a diet structure dominated by cheap staple carbohydrates, while people with better economic conditions more easily access higher-cost protein sources like meat and dairy. Just like herbivores primarily consume plants while predators feed on meat, human dietary structures to some extent also reflect resource acquisition capability: protein is more conducive to maintaining muscle, while excess carbohydrates more easily convert to fat storage.