Cao Tingdong was sickly since childhood, so he paid more attention to the study of health preservation. At the age of seventy-five, he was "obsessed with thinness". Because of the "old saying", he remembered his own way of keeping in good health.

The book Lao Lao Heng Yan consists of five volumes, of which the first volume is about sleeping, waking up in the morning, washing, eating, eating, walking, lying down during the day and sitting at night, the second volume is about staying at home, worrying, seeing guests, going out, preventing diseases, being cautious about medicine, entertainment and guidance, and the third volume is about libraries, books, sitting on couches, sticks, clothes and so on.

This book continues the idea of keeping in good health in Huangdi Neijing and forms a distinct style of keeping in good health. His idea of health preservation is mainly reflected in the following aspects: putting quietness first, nourishing the heart first, being good at rejuvenation, paying attention to diet and living, and conforming to nature. In addition, compared with other health books, Lao Lao Heng Yan also embodies the characteristics of "quoting a lot", "being brave in criticism", "experiencing personally" and "not doing empty things".