Low body fat: When body fat is low, veins are less covered by tissue, making them more visible. This is common in athletes and people in good physical condition.
Genetics: Some people naturally have thinner or more transparent skin, which allows veins to be more visible.
Physical activity: Exercise increases blood flow and causes temporary dilation of the veins, making them more visible during or after exertion.
Aging: With age, the skin thins and loses its elasticity, which can make veins more visible, especially on the hands and legs.
Body temperature: Heat causes blood vessels to dilate, which can make veins more visible under the skin.
In general, visible veins are more of a normal physical characteristic than a sign of a health problem.