When I was a child, I didn't know the benefits of being slightly fat, and I mistook thin monkeys for treasures. It implies people's misunderstanding and prejudice about the body standard, thinking that thinness is beauty, while ignoring health and diversity. A slightly chubby figure refers to a slightly fleshy figure, neither too thin nor too fat, which is a healthy figure. Pencil necked refers to a thin figure and may have health problems. So this sentence reminds people to look at their figure correctly, not blindly pursuing thinness, but paying attention to health and diversity.