Which of the following is NOT a classic risk factor for cholelithiasis?

Cholelithiasis, or the formation of gallstones, is commonly influenced by various risk factors. Among these, obesity, female gender, and multiparity are well-established contributors. Obesity increases cholesterol saturation in bile, providing a conducive environment for gallstone formation. The female gender is associated with hormonal factors, such as estrogen levels, which can also promote gallstone development. Multiparity, or having multiple pregnancies, is linked to hormonal changes that can increase the risk of gallstones as well.

Being under the age of 30 is not recognized as a classic risk factor for cholelithiasis. Gallstones are more prevalent in older adults, especially those over 40, and the incidence tends to increase with age. Therefore, individuals under 30 are generally at a lower risk of developing gallstones, making this choice the least aligned with the classic risk factors.