Main exposure: weight change

Of the 30,445 men and women, aged 39–79 years, who consented to participate in the study (39% response rate), 25,639 attended a baseline health examination (1HE) between 1993 and 1997 and 15,786 attended a second health examination (2HE) between 1998 and 2000.

At both health examinations, a trained nurse measured weight (to the nearest 0.1 kg) and height (to the nearest 0.1 cm), with participants wearing light clothing and no shoes. Body mass index (BMI) was calculated as weight divided by the square of height (kg/m²).

Absolute weight change was calculated as weight (kg) measured at 2HE minus weight (kg) measured at 1HE. Participants were assigned to one of 6 weight change categories: > 5 kg loss, > 2.5–5 kg loss, within 2.5 kg loss or gain (‘maintenance’, considered the reference category), > 2.5–5 kg gain, > 5–10 kg gain, > 10 kg gain.

Annual weight and BMI changes were calculated from the absolute differences in weight and BMI respectively, divided by the participants’ time lapse between the health examinations (kg/year and kg/m²/year respectively).