English:
Weight in the Balance: Evaluation of a video and textual web-based tailored intervention aimed to prevent obesity.

Dutch:
Gewicht in Balans: Evaluatie van een video en tekstuele computer-getailorde interventie gericht op de preventie van obesitas.

The purpose of this trial is to evaluate two different web-based tailored interventions aimed to prevent obesity among adult blue and white collar workers with a BMI between 18.5 and 30.

The text-text intervention consists of tailored textual core messages as well as additional in-depth textual information regarding body weight, nutrition, and physical activity. The video-text intervention has exactly the same content, but the core messages will be delivered by means of videos. The interventions consist of six sessions, in which participants receive tailored messages and information to help them manage their weight. The content of the intervention is based on many principles of self-regulation theories with the aim to help users develop skills and competencies to improve their physical activity level and/or dietary intake. The focus of the intervention is on small improvements in physical activity and/or dietary intake. By making small improvements, individuals can maintain their current weight or loose a little weight (about five kilos in one year). Participants are free to choose whether they want to maintain their weight or loose a little weight as well as whether they want to increase their physical activity level and/or improve their dietary intake.

The hypothesis is that the video-text intervention will be more effective in the prevention of weight gain or achieving modest weight loss for employees with a relatively low level of education, whereas the text-text intervention will be more effective for employees with a relatively high level of education. Further, moderation of the intervention effects through demographic characteristics, information processing style, self-efficacy, and planning will be explored as well as mediation of the intervention effects through self-regulation skills and message characteristics.
The study will be carried out using a randomized controlled trial, with a baseline measurement and two follow-up measurements at 6 and 12 months. Potential participants will be recruited by employees of occupational health services during health checks. We aim to recruit at least 2.000 participants at baseline.

We have obtained a declaration of no objection that the present study does not require MEC approval.

1. The video-text web-based tailored intervention will be more effective in the prevention of weight gain or achieving modest weight loss among lower educated workers;

2. The text-text web-based tailored intervention will be more effective in the prevention of weight gain or achieving modest weight loss among higher educated workers;

3. Both the video-text as the text-text web-based tailored intervention will be more effective in the prevention of weight gain or achieving modest weight loss compared to the control condition;

4. Moderation of the intervention effects through demographic characteristics, information processing style, self-efficacy, and planning will be explored;

5. Mediation of the intervention effects through self-regulation skills and message characteristics will be explored.

T0: 2 weeks before start intervention;

T1: 6 months after baseline;

T2: 12 months after baseline.

The study compares the effects of two different web-based tailored interventions (text-text and video-text condition) with a control condition.



Text-text condition:

Participants in this condition will receive a web-based tailored intervention consisting of textual core messages as well as additional in-depth textual information regarding body weight, nutrition, and physical activity. The intervention consists of six sessions, in which participants receive tailored messages and information to help them manage their weight. The content of the intervention is based on many principles of self-regulation theories with the aim to help users develop skills and competencies to improve their physical activity level and/or dietary intake. The focus of the intervention is on small improvements in physical activity and/or dietary intake. By making small improvements, individuals can maintain their current weight or loose a little weight (about five kilos in one year). Participants are free to choose whether they want to maintain their weight or loose a little weight as well as whether they want to increase their physical activity level and/or improve their dietary intake.



Video-text condition:

This intervention is the same as the text-text intervention, with the difference that the core messages are delivered by means of videos instead of text.



Control condition:

Participants in the control condition will not receive any information or treatment.