Immediate and 15-Week Correlates of Individual Commitment to a “Green Monday” National Campaign Fostering Weekly Substitution of Meat and Fish by Other Nutrients

Promoting healthier and more sustainable diets by decreasing meat consumption represents a significant challenge in the Anthropocene epoch. However, data are scarce regarding the effects of nationwide meat reduction campaigns. We described and analyzed the correlates of a national campaign in France (called “Green Monday”, GM) promoting the weekly substitution of meat and fish by other nutrients. Two cross-sectional online surveys were compared: a National Comparison sample (NC) of the French general population and a self-selected sample of participants who registered for the Green Monday campaign. A follow-up study was carried out in the GM sample, in which participants were asked during 15 weeks whether or not they had substituted meat and fish. There were 2005 participants aged 18–95 (47.7% females) in the NC sample and 24,507 participants aged 18–95 (77.5% females) in the GM sample. One month after the beginning of the campaign, 51.2% of the respondents reported they had heard about Green Monday in the NC sample, and 10.5% indicated they had already started to apply Green Monday. Logistic regression analysis showed that compared to the NC sample, participants belonging to the GM sample displayed a higher rate of females, Odds Ratio (OR) = 4.26, 95% Confidence Interval (CI): 3.86–4.71, were more educated, OR = 1.32, 95% CI: 1.28–1.36, had higher self-rated affluence, OR = 1.50, 95% CI: 1.42–1.58 and the size of their vegetarian network was greater, OR = 1.50, 95% CI: 1.41–1.58. They reported a slightly higher frequency of meat consumption, OR = 1.05, 95% CI: 1.01–1.10, while their frequency of fish consumption was lower, OR = 0.81, 95% CI: 0.76–0.87. Finally, the personality dimension Openness was more strongly endorsed by participants in the GM sample, OR = 1.79, 95% CI: 1.65–1.93. A multiple regression analysis indicated that Openness also predicted the number of participation weeks in the GM Sample (beta = 0.03, p < 0.009). In conclusion, specific demographic and personality profiles were more responsive to the national campaign, which could inform and help to shape future actions aiming at changing food habits.