The hourglass figure gives people the impression of being very curvaceous. The hourglass figure is the X-shaped figure in the letter figure. Girls with an hourglass figure have plumper breasts and hips, wider shoulders, and the width of the hips and shoulders is about the same. However, the waist is slender, making the whole person look forward and backward, very sexy. Studies have shown that sex hormones affect fat accumulation. Estrogen, the female hormone, can inhibit the accumulation of fat in the upper abdomen and increase the accumulation of fat in the buttocks and thighs. Therefore, adult men and adult women have completely opposite physical characteristics in the waist, hips and thighs due to the effects of different hormones. Waist-to-hip ratio is an easy-to-observe, stable indicator that reflects internal physiological processes.