Time trends (1993-1997) and seasonal variation in body mass index and waist circumference in the Netherlands

OBJECTIVE: To compare the time trend and seasonal variation in body mass index (BMI) and waist circumference. DESIGN: Continuous monitoring health survey carried out between 1 June 1993 and 31 May 1997. SUBJECTS: A total of 8186 men and 9638 women aged 20-59 y from three towns in the Netherlands. MEASUREMENTS: BMI and waist circumference. Obesity was defined as BMI greater than or equal to30 kg/m(2), abdominal obesity as waist circumference greater than or equal to102 cm for men and greater than or equal to88 cm for women. RESULTS: Levels of BMI and waist circumference increased between 1 June 1993 and 31 May 1997. Among women, the time trend in abdominal obesity was stronger than that in obesity. Further, levels of BMI and waist circumference were higher in winter than in summer seasons. The seasonal variation was larger for abdominal obesity than for obesity, among both men and women. CONCLUSIONS: The time trend in women and the seasonal differences in both men and women were stronger for abdominal obesity than for obesity. Surveys on BMI and waist circumference are only comparable if season is taken into account. Furthermore, the waist circumference is a more sensitive indicator of variations in lifestyle and body composition than is body mass index.