Primary school children who took part in this research had a mean age of 7.1 ± 0.6 years, 51.2% of them were boys. Table 1 shows the baseline characteristics of the participants. Significant differences between boys and girls occurred in anthropometric variables where boys had a slightly higher waist circumference but were less frequently at or above the 95th percentile for %body fat. They also had a different distribution of WHtR with a lower variance and range than girls. Boys more often played outside and reached higher levels of physical activity. Girls more often skipped breakfast than boys.Table 1Baseline characteristics of participants in the Baden-Württemberg Study (2010)MissingBoysGirlsTotalValues(n = 995)(n = 948)(n = 1,943)Child characteristics Age, years [m (sd)]7.09 (0.64)7.06 (0.63)7.08 (0.64) Migration background, n (%)297255 (30.9)270 (32.9)525 (31.9) BMIPERC, [m (sd)]5048.78 (27.87)49.14 (27.92)48.96 (27.89) Overweight, n (%)5054 (5.6)54 (5.9)108 (5.7) Obesity, n (%)5049 (5.1)34 (3.7)83 (4.4) Waist circumference, [m (sd)]5555.98 (5.83)***a 55.16 (5.90)55.58 (5.88) WHtR, [m (sd)]550.45 (0.04)*0.45 (0.04)0.45 (0.04) Abdominal obesity, n (%)5573 (7.5)85 (9.2)158 (8.4) ≥ 95th percentile for %body fat, n (%)55128 (13.2)***a 211 (22.9)339 (18.0)Parental characteristics Single parent, n (%)26582 (9.7)95 (11.4)177 (10.5) Tertiary family educational level, n (%)215262 (31.8)261 (32.5)523 (32.1) Household income ≤ €1,750, n (%)452101 (13.4)106 (14.4)207 (13.9) Overweight/obesity (mother or father), n (%)332532 (65.0)542 (68.3)1074 (66.7) Abdominal obesity (mother or father), n (%)974405 (82.7)407 (85.0)812 (83.8) Smoking (mother or father), n (%)270309 (36.9)319 (38.2)628 (37.5) Health awareness (mother or father), n (%)343541 (67.4)539 (67.6)1080 (67.5)Health and lifestyle characteristics Skipping breakfast, n (%)23689 (10.4)**134 (15.8)223 (13.1) Soft drinks > 1/week, n (%)241219 (25.6)197 (23.3)416 (24.4) Playing outside > 60 min/day, n (%)296615 (73.8)***515 (63.3)1130 (68.6) Physically active ≥ 4 days/week ≥ 60 min/day, n (%)320260 (31.7)***177 (22.1)437 (26.9) Club sports > 1/week, n (%)662338 (52.0)338 (53.6)676 (52.8) Screen media > 1 h/day, n (%)250173 (20.4)146 (17.3)319 (18.8) NOTE. m mean, sd standard deviation, BMI body mass index, BMIPERC BMI percentiles, WHtR waist-to-height ratio aMann–Whitney-U test, *p < 0.05, **p < 0.01, ***p < 0.001