The prevalence of objectively assessed overweight and obesity among Swiss children was significantly lower than across the other European countries in the ENERGY-consortium. Reported physical activity and screen viewing behaviors were more favorable whereas dietary habits were similar. Within the Swiss sample, ethnicity was more strongly related to differences in overweight prevalence, dietary habits, active commuting and screen activities than parental education or gender.
The prevalence of overweight and obesity observed in the present study are in line with more recent Swiss studies based on measured weight and height
[21, 22] but are clearly higher than the rates of the HBSC study which were based on self-reports of the children
. Studies assessing time trends of childhood overweight prevalence in Switzerland based on measured weight and height documented a strong increase during the nineties of the last century
 and a ‘leveling off’ or even decrease since the beginning of the new century
[2, 21–23]. This trend is in line with the results of a recent review analyzing data of 52 studies from Australia, Europe, Japan and the USA
Within the Swiss sample no statistical significant gender difference in the prevalence of overweight and obesity was found, but ethnicity appeared as a strong risk factor as previously reported
[21, 23–25]. However, non-native Swiss children had a significantly lower BMI, waist circumference and proportion of overweight than the average across the ENERGY-countries.
In contrast to the previous report of the HBSC study
 the present study showed that Swiss children accumulated significantly more minutes of active commuting and of participation in sports activities than the other ENERGY-Partners. These results are supported by the recently published accelerometer measurements of the ENERGY project
 indicating that Swiss children spent significantly more minutes in moderate to vigorous physical activity than children from the other European countries. There might be several explanations for these findings. First, all schools in Switzerland are legally obligated to provide 3 physical education sessions per week and although children only spend one third of these lessons in moderate to vigorous physical activity, they significantly increase children’s accelerometer based MVPA levels during school time
. Secondly, there is a national sports promotion program ‘ Youth and Sport (Y+S)’ which offers optional physical education sessions after school as well as courses and sport camps for children and fosters children’s integration into a sports club
. Third, a vast proportion of Swiss children still commutes actively to school
[29, 30]. The results of the present study might even underestimate the time spent in active commuting as they are based on the ENERGY algorithm to calculate total commute time assuming two trips per day. Yet, children in Switzerland usually return home for lunch and therefore travel up to four times a day to or from school. Active commuting to school is popular in Switzerland since more than 95% of the Swiss children attend the public schools located closest to their homes
 and there is no free school choice. The short distances facilitate walking or cycling to school. In addition, 64% of parents reported to perceive their children’s way to school to be safe
. Safety concerns of Swiss parents were mostly related to dangers from traffic (85%) and less often to violence and harassment (<10%)
 contrasting reports, e.g. from the UK, where a large proportion of parents were worried about abduction or molestation
Swiss children also indicated to spend less time with screen activities than their peers in the seven European ENERGY-Partners’ countries as also reported by the HBCS study
. Screen-viewing behaviors are usually assessed as an indicator of physical inactivity. Yet, recent comparisons with accelerometer-derived sedentary time clearly showed that self-reported TV and computer time did not correlate well with objective measures
[32, 33]. TV viewing may not be a good indicator of physical inactivity but it has been linked to unhealthy eating behaviors, such as lower fruit and vegetable intake, higher sugar-sweetened beverage consumption snacking and higher fast food intake
 which in turn are related to overweight.
Interestingly EBRB of non native Swiss children were in most aspects comparable to the behaviour of Swiss native children (active transport, sleeping duration, screen activities) indicating some adoptive behaviour. An exception was cycling where non-native Swiss resembled more the one from southern Europe ENERGY Partners (Greece, Spain).
Strength and limitations
An obvious limitation and potential source of bias of the present study is the low participation rate. First, the relatively small sample size reduced our ability to detect statistically significant differences between sub-groups. Second, overweight/ obesity and EBRB rates may be underestimated if participation in the study was dependent on overweight status or behavioral patterns. To address this question we evaluated whether the response rate in a given school was associated with the prevalence of overweight assuming that in schools with low participation rate a lower prevalence of overweight would result. Response rates in our samples varied between 20% and 81% and were subdivided into quartiles. The quartile with the lowest participation rate (1st quartile) yielded an overweight prevalence of 25.5%, the 2nd quartile 15.6%; the 3rd quartile 7.2%; and the 4th quartile a rate of 13.1%, thus giving no evidence of a systematic under-representation of overweight children due to selective participation. Third, the assessment of dietary habits, physical activity and sedentary behavior were self-reported and depended upon the respondents’ recall and ability to give correct answers. We thus evaluated the test-retest reliability and construct validity of the respective questions and found good levels of agreement similar to those of the ENERGY-Partners
. Finally the three regions included in the ENERGY study were all from the German speaking part of Switzerland (63.7% of the Swiss people) limiting the generalization for the whole country.
A clear strength of the present study was the use of the standardized ENERGY protocol allowing international comparisons and the inclusion of objective weight and height data.