Warschburger and Kröller BMC Public Health 2012, 12:295 http://www.biomedcentral.com/1471-2458/12/295 and the associated health problems [5-8]. Factors predict- ing the underestimation of weight and risk status of the child are the child’s young age, rapid weight gain in infancy, the mother’s and child’s higher weight status, as well as lower educational attainment and an African- American background [9-15]. The correct identification of a child’s weight status seems to be relevant if any change in weight is recommended: in a prospective study, Kroke et al. [16] showed that children who were correctly identi- fied as overweight at 6 months of age by their mothers had a greater decrease in the standardized BMI (BMI- SDS) than those who were not correctly identified. Accurate weight estimation seems to be necessary but not sufficient for employing prevention or intervention strategies. Myers and Vargas [17] found that 37% of par- ents, though correctly recognizing their child’s overweight, had nevertheless taken no action to change it. One explan- ation for this discrepancy is parental failure to associate their child’s weight status with higher health risks. We are only aware of two studies exploring factors associated with parental readiness for change. Rhee, DeLago, Arscott-Mills, Mehta and Davis [18] focused on parents with overweight children aged 2 to 12 years: 44% were not interested in making lifestyle changes to help their child lose weight within the next 6 months. Aside from the child’s age, higher readiness for change was associated with the belief that their child’s weight constituted a health problem. Crawford, Timperio, Telford and Salford [19] even reported that par- ental concern about the future – but not the actual weight status of their child – increased parents’ use of prevention strategies. The discrepancy between the parental preferred and perceived weight status of their child is an additional mo- tivational incentive discussed in the literature. A parental preference for their child to have a slender silhouette has been associated with an earlier perception of the need for preventive activities [20-22]. There is an increasing awareness of the impact of parental risk perception on the weight course of the child and the parent’s readiness to engage in pre- ventive efforts. Although a few studies have pointed out that risk perception does not necessarily lead to intervention, less is known about factors related to the parental perception of the right time for the im- plementation of preventive activities. The objectives of the present study were to determine at which weight status mothers perceived that actions for pre- venting their child’s overweight became necessary, as well as the factors associated with different weight statuses at which mothers perceive the need for pre- vention efforts. Based on the existing research we hypothesized that parents would decide that action was needed based on their general perception of the risk associated with overweight, their own weight Page 2 of 8 status and that of the child, as well as maternal dis- satisfaction with the child’s current weight status. Methods Procedure As part of a larger study of childhood obesity prevention (supported by BMBFa project number 01EL0408), a ques- tionnaire was administered to mothers between February and October 2007. Participants were recruited in roughly equal parts from inpatient clinics (e.g. those specializing in child rehabilitation for respiratory diseases, dermatitis or susceptibility to infections), child care centers, and online communities. Eligible participants were mothers of children aged one to ten who had no health-related dietary restric- tions. In order to make participation more convenient, the questionnaire was available either online or in a pencil-and- paper version, and participants were free to choose their preferred format. Depending on the place from which the mothers were recruited, they filled in the paper-and-pencil version in the clinic or child care center and returned it to the office, they filled it out at home and returned it later, or they completed the online version, which could be filled in and sent from their personal computer. On average, mothers needed fifteen minutes to finish the questionnaire, which included about 120 items. Mothers who have more children in the indicated age range were requested to select one, that we could analyze mother-child pairs. This study was approved by the University of Potsdam institutional ethics committee and has therefore been performed in accordance with the ethical standards of the 1964 Declaration of Helsinki. Measures Socio-demographic variables Mothers provided details concerning their marital status, age and education as well as their child’s sex and age. Family’s net income (including unemployment, housing, maternity or sick leave benefits, pensions, and wages or comparable earnings) was calculated, taking into account the current number of family members in the household. The graduation level is the number of years of school the mother completed. Weight status All mothers reported their own height and weight as well as the height and weight of their child. Accordingly, these reported heights and weights were used to calculate subjects’ BMIs. For children, we used BMI per- centiles and a standardized BMI (BMI-SDS) according to age and sex [23]. The classification of children as overweight (BMI percentile > 90) was done according to national guidelines [24].