The effects of smoking, drinking too much and not exercising enough are felt by the age of 36, researchers have warned.
By stopping these behaviours early in adulthood and midlife, years of subsequent ill health can be prevented, according to the study, which tracked people for more than 30 years.
Smoking causes lung cancer and heart and breathing problems, while a lack of exercise and too much alcohol are linked to issues such as cancer, stroke, heart attacks and early death.
In the new research, published in the Annals of Medicine, experts from Finnish universities found that people as young as 36 were showing signs of poor health choices.
The team tracked 326 people when they were 27 years old and again when they were aged 36, 42, 50, and 61 (when 206 people were included).