Trial Information

A New Concept for Lifestyle Change, Dietary Advice on Prescription (DAP) in Combination With Motivational Interviewing (MI), Social Support and Mobile Services

The investigators assume a difference in BMI (body mass index; kg/m x m) of 2 units, a
standard deviation of 4.5 units, a power of 80 %, an alfa error of 5 % I a two-tailed test,
the investigators would need at least 80 individuals in the experimental group and in the
control group, respectively.

With 80 individuals in each group and the assumption of 5 % adherence (4 individuals) in the
control group, the investigators would be able to detect an adherence of 21 % or higher (at
least 17 individuals) in the experimental group with 80 % power. The alfa error is set to 5
% in a two-tailed test with the null hypothesis that the adherence is the same in both
groups.

Therefore the investigators plan a study with at least 100 individuals in each group and
assume that 20 % will not complete the study.

The evaluation of the quantitative studies will be performed in three ways: 1) Process
evaluation, that will focus on intermediate outcomes such as knowledge, attitudes,
motivation and readiness for change. 2) Effect evaluation will be used to evaluate the
effect of the intervention programme on the subjects' behavior such as dietary intake and
physical activity level. 3) Outcome evaluation will measure the total effect of the
intervention programme, in this case variables that measures indicators for health and
disease, such as SF-36, EQ-5D, SHIS, serum cholesterol, blood pressure, BMI, waist
circumference etc.

Intention-to-treat (ITT) analysis will be used to assess effects on outcome measures.
Variables not normally distributed will be logarithmically transformed. Paired t-test will
be used to assess change within groups and unpaired t-tests to compare mean changes between
groups. Non-parametric statistics, Wilcoxon Signed Ranks Test and Mann-Whitney U-Test will
be used for ordinal data such as questionnaires. Two-tailed tests will be used and a p-value
less than 0.05 will be considered statistically significant.

Qualitative data will be analyzed by content analysis.