The effectiveness of the Lifestyle Triple P intervention is being tested in the southern part of the Dutch province of Limburg, using an RCT design. After baseline measurements, parents of overweight children are randomly allocated to either the intervention group or the control group. The intervention group receives the Lifestyle Triple P intervention, whereas parents in the control group receive information on healthy nutrition, physical activity, and positive parenting. To evaluate the effect of the intervention, participants are measured again immediately following the intervention (4 months after baseline), and at 12 months after baseline (see Figure 1 for the study design). Baseline measurements and intervention groups are started as soon as enough participants per location have been recruited (i.e. a minimum of 10: 5 for the control group and 5 for the intervention group). The Medical Ethics Committee of the University Hospital Maastricht and Maastricht University approved the study protocol (reference number NL 31988.068.10 / MEC 10-3-052).
The Southern Limburg regions has 608,885 inhabitants , 49.8% (303,225) of whom live in the municipalities of Maastricht, Sittard-Geleen and Heerlen. About 10% are aged 4 to 8 years. The estimated prevalences of overweight and obesity in the 4–8 year age group are 9.5% and 2.3% respectively, implying an eligible population of 3,578 children for the current study.
Recruitment of the study sample
The participants are being recruited using four strategies: two strategies that use the Dutch Youth Health Care (YHC) system, one using mass media and one using personal letters. Health professionals working in the YHC system have been instructed to refer parents of overweight children to the Lifestyle Triple P intervention. In addition, parents of children who are overweight according to the YHC’s medical records have been approached for participation in the intervention. Finally, mass media materials (a brochure, a poster, advertisements in newspapers, and a website) have been developed to inform parents about the intervention and to offer them the opportunity to register for the intervention. We have also sent invitation letters to parents of primary school children. Recruitment of participants for the current RCT started in December 2010.
We aim to recruit a study population of 84 child-parents triads. Parents of children aged between 4 and 8 years (at inclusion) are eligible for participation if their child is considered overweight or obese, based on the BMI, using the international sex- and age-specific cut-off points proposed by Cole et al . Parents who agree to participate in the study and both sign the informed consent form are included in the current study.
The sample size calculation was based on the difference between the intervention condition and the control condition in terms of BMI points. A difference of 0.30 BMI points between the intervention and control conditions was expected to be relevant, based on previous studies, e.g. Robinson 1999 . Based on an alpha value of 0.05 and a power of 0.90, adjusting for attrition and nesting effects within the groups, we aimed to randomly assign 84 families to the 6 Lifestyle Triple P groups (intervention) or to the control condition.
The randomization scheme has been generated by an independent researcher (PCD), who is not directly involved in the data collection or intervention delivery, using a block size of four and sealed envelopes. The randomization is concealed to all other members of the study team. After baseline measurements, participants are randomly allocated to either the intervention or the control condition. A member of the study team (SMPLG), who is blinded to the randomization scheme, calls the research institute by telephone in the presence of the parents to enquire for their group allocation, and then informs the parents.
Lifestyle Triple P Intervention
Key objectives of the Lifestyle Triple P intervention are:
improving children’s dietary intake, activity levels, and weight status;
increasing parenting skills and confidence in managing children’s weight-related behavior;
reducing parents’ use of coercive and permissive discipline practices to their children;
improving parents’ communication about health and nutrition;
reducing parenting stress associated with raising healthy children.
The participants who are assigned to the intervention condition receive a 14-week Lifestyle Triple P intervention which consists of eight weekly 90-minute parental group sessions, followed by two weekly 15–30 minute telephone sessions, one further 90-minute group session, two weekly 15–30 minute telephone sessions, and a final 90-minute group session. The groups are composed of either one or both parents of at most 9 families, and each group is led by two Lifestyle Triple P facilitators. These are health professionals who have been accredited after attending an official 3-day Triple P training course and an additional Lifestyle Triple P training day. The group sessions take place at three different buildings of the regional Public Health Services (at Heerlen, Geleen, and Maastricht). To ensure intervention fidelity (defined as the extent to which the intervention is implemented as intended ), the facilitators meet on a regular basis with a member of the study team (SMPLG) for supervision. Participation in the intervention is free of charge. Each family is provided with a parent workbook, a recipe book, and an active games booklet to support the information presented in the sessions. All the materials have been translated into Dutch for the current trial, according to the following process. First, translators of Triple P International translated the materials from English to Dutch. Hereafter, all translations were reviewed by a native Dutch speaker (SMPLG). The translation and reviewing process were conducted in line with already existing Dutch Triple P materials. A pilot study was undertaken to test specific parts of the Lifestyle Triple P intervention for feasibility and acceptability.
Lifestyle Triple is a family intervention strategy to prevent and treat childhood obesity. The intervention consists of active skills training methods based on self-regulation principles, to provide parents with new knowledge and skills. In the first sessions, parents individually formulate realistic goals for change, with the help of the trainer and based on their child’s dietary intake and activity levels. Parents are instructed on a range of nutrition strategies (e.g., establishing eating routines and providing healthy foods), physical activity strategies (e.g., providing active games and playing with your child), and positive parenting strategies (e.g., spending quality time with your child and giving frequent praise). An overview of the intervention topics is shown in Table 1. The telephone sessions aim to provide parents with individual support in the implementation of strategies at home.
Participants who are randomized to the control condition receive two brochures (one on healthy nutrition and physical activity, and one on positive parenting), web-based tailored advice on setting a good example to their child, and suggestions for exercises to increase active play at home.
Outcome measures are assessed at baseline (one or two weeks before the start of the intervention), at 4 months (immediately after the intervention), and at one year follow-up. Primary outcome measure is children’s body composition, operationalized as BMI z-score, waist circumference, and fat mass. Secondary outcome measures are children’s dietary behavior and physical activity level, parenting practices, parental feeding style, parenting styles, parental self-efficacy, and body composition of family members (parents and siblings).
Anthropometric measurements in the children are conducted during a visit to the Public Health Service office. If one or both parents are willing to participate, they are measured as well. In addition, if siblings (if applicable) are present at the visit and are willing to participate, they are also measured. Measurements are performed by a YHC professional who is blinded for group allocation, using a standardized protocol. The participating YHC professional has many years of experience in performing body measurements and has attended a one-day training course to perform the measurements in accordance with the protocol.
Weight is measured using an electronic portable scale (standardized Seca 899) to the nearest 0.1 kg, with the subject wearing only underwear. Height is measured using a portable stadiometer (Seca 214) with an accuracy of 1 mm. Both measurements are used to calculate BMI and BMI z-scores. Waist circumference is measured with a flexible tape to the nearest 1 mm. Biceps and triceps skinfold thickness is measured to the nearest 0.1 mm using a Harpenden skinfold caliper. Each skinfold is measured three times and the median is used. If two of the scores differ by more than 10%, another three skinfolds are measured, and the median of the six values is used.
Children’s physical activity levels are measured using an Actigraph accelerometer (Actigraph, Pensacola, Florida). Children are asked to wear the accelerometer for seven consecutive days, preferably in the week after the anthropometric measurements. The epoch (time frame) is set at 15 sec.
Parents are asked to fill out a questionnaire at baseline, at posttest and at one year follow-up. The questionnaire has been compiled from validated scales, and assesses the following variables:
Demographics: gender, age, household and family composition, educational level of the parents, ethnicity of the child and the parents, and work situation of the parents;
Energy balance-related behaviors of the child: screen-viewing behavior, snacking behavior, soft-drink consumption, fruit and vegetable consumption and physical activity level ;
Parenting practices: monitoring, restriction, pressure to eat, and perceived responsibility ;
Parental feeding style: instrumental feeding, emotional feeding, control, and encouragement ;
Parenting style: restrictiveness and nurturance  and psychological control ;
Parenting self-efficacy: satisfaction about one’s own efficacy and effectiveness at solving problems ;
Personality characteristics of the child: surgency/extraversion, negative affectivity, and effortful control .
Parental satisfaction with the intervention is measured by including process evaluation questions in the post-test questionnaire at 4 months, and questions about changes in problem behavior and management of problem behavior in the 1-year questionnaire.
Descriptive statistics will be used to describe subject characteristics, including baseline values of primary and secondary outcome measures. Continuous variables will be presented as means and standard deviations. Categorical data will be presented as percentages of respondents within each of the possible categories.
Both univariate and multivariate multilevel analyses (to control for potential nesting effects within the Lifestyle Triple P groups) will be conducted to determine the effect of the intervention on changes in children’s BMI z-score, children’s waist circumference, children’s fat mass, children’s lifestyle (screen-viewing behavior, snacking behavior, soft-drink consumption, fruit and vegetable consumption, and physical activity level), parenting self-efficacy, parental skills, and the BMI, waist circumference, and fat mass of both the parents and the siblings. All analyses will be performed according to intention-to-treat analyses, and additional per protocol analyses will be performed. Models will be adjusted for relevant confounders such as children’s age, gender, and ethnicity, and parental socio-economic status.