1. Emely de Vet, PhD is with the Institute of Health Sciences, VU University, Amsterdam, the Netherlands. Johannes Brug, PhD is with the EMGO Institute, VU University Medical Centre, Amsterdam, the Netherlands. Anke Oenema, PhD, is with the Department of Public Health, Erasmus MC University Medical Center, Rotterdam, the Netherlands. Jascha de Nooijer, PhD; and Nanne K. de Vries, PhD, are with the Department of Health Education and Promotion, Universiteit Maastricht, Maastricht, the Netherlands