Who benefits from a dietary online intervention? Evidence from Italy, Spain and Greece

Abstract

Objective: The traditional Mediterranean diet includes high consumption of fruits, vegetables, olive oil, legumes, cereals and nuts, moderate to high intake of fish and dairy products, and low consumption of meat products. Intervention effects to improve adoption of this diet may vary in terms of individuals' motivational or volitional prerequisites. In the context of a three-country research collaboration, intervention effects on these psychological constructs for increasing adoption of the Mediterranean diet were examined.

Design: An intervention was conducted to improve Mediterranean diet consumption with a two-month follow-up. Linear multiple-level models examined which psychological constructs (outcome expectancies, planning, action control and stage of change) were associated with changes in diet scores.

Setting: Web-based intervention in Italy, Spain and Greece.

Subjects: Adults (n 454; mean age 42·2 (sd 10·4) years, range 18-65 years; n 112 at follow-up).

Results: Analyses yielded an overall increase in the Mediterranean diet scores. Moreover, there were interactions between time and all four psychological constructs on these changes. Participants with lower levels of baseline outcome expectancies, planning, action control and stage of change were found to show steeper slopes, thus greater behavioural adoption, than those who started out with higher levels.

Conclusions: The intervention produced overall improvements in Mediterranean diet consumption, with outcome expectancies, planning, action control and stage of change operating as moderators, indicating that those with lower motivational or volitional prerequisites gained more from the online intervention. Individual differences in participants' readiness for change need to be taken into account to gauge who would benefit most from the given treatment.

Keywords: Action control; Action planning; Dietary change; Digital intervention; Online survey; Outcome expectancies; Stages of change.

Fig. 1

Mean level changes in dietary behaviours (MEDAS sum scores) moderated by HAPA stages of change, controlling for age, sex and BMI, among adults (mean age 42·2 (sd 10·4) years, range 18–65 years; n 454 at T1, n 112 at T2) participating in a web-based intervention in Italy, Spain, and Greece, 2015. Less motivated persons have a steeper slope, which means that they gain more from the treatment (MEDAS, Mediterranean Diet Adherence Screener; HAPA, Health Action Process Approach; T1, baseline; T2, follow-up)

Fig. 2

Mean level changes in dietary behaviours (MEDAS sum scores) moderated by positive dietary outcome expectancies, controlling for age, sex and BMI, among adults (mean age 42·2 (sd 10·4) years, range 18–65 years; n 454 at T1, n 112 at T2) participating in a web-based intervention in Italy, Spain and Greece, 2015. Persons who hold less positive outcome expectancies have a steeper slope, which means that they gain more from the treatment (MEDAS, Mediterranean Diet Adherence Screener; T1, baseline; T2, follow-up)

Fig. 3

Mean level changes in dietary behaviours (MEDAS sum scores) moderated by dietary planning, controlling for age, sex and BMI, among adults (mean age 42·2 (sd 10·4) years, range 18–65 years; n 454 at T1, n 112 at T2) participating in a web-based intervention in Italy, Spain and Greece, 2015. Persons who initially were less prone to plan their diet have a steeper slope, which means that they gain more from the treatment (MEDAS, Mediterranean Diet Adherence Screener; T1, baseline; T2, follow-up)

Fig. 4

Mean level changes in dietary behaviours (MEDAS sum scores) moderated by dietary action control, controlling for age, sex and BMI, among adults (mean age 42·2 (sd 10·4) years, range 18–65 years; n 454 at T1, n 112 at T2) participating in a web-based intervention in Italy, Spain and Greece, 2015. Persons who initially were less aware of their dietary behaviour patterns have a steeper slope, which means that they gain more from the treatment (MEDAS, Mediterranean Diet Adherence Screener; T1, baseline; T2, follow-up)