Background Since December 2019, coronavirus disease 2019 (COVID-19) has been spreading steadily, resulting in overwhelmed health-care systems and numerous deaths worldwide. To counter these outcomes, many countries, including France, put in place strict lockdown measures, requiring the temporary closure of all but essential places and causing an unprecedented disruption of daily life. Objectives Our objective was to explore potential changes in dietary intake, physical activity, body weight, and food supply during the COVID-19 lockdown and how these differed according to individual characteristics. Methods The analyses included 37,252 adults from the French web-based NutriNet-Santé cohort who completed lockdown-specific questionnaires in April–May 2020. Nutrition-related changes and their sociodemographic, lifestyle, and health-status correlates were investigated using multivariable logistic regression models. Clusters of participants were defined using an ascending hierarchical classification of change profiles derived from multiple correspondence analyses. Results During the lockdown, trends of unfavorable changes were observed: decreased physical activity (reported by 53% of the participants), increased sedentary time (reported by 63%), increased snacking, decreased consumption of fresh food (especially fruit and fish), and increased consumption of sweets, cookies, and cakes. Yet, the opposite trends were also observed: increased home cooking (reported by 40%) and increased physical activity (reported by 19%). Additionally, 35% of the participants gained weight (mean weight gain in these individuals, 1.8 kg ± SD 1.3 kg) and 23% lost weight (2 kg ± SD 1.4 kg weight loss). All of these trends displayed associations with various individual characteristics. Conclusions These results suggest that nutrition-related changes occurred during the lockdown in both unfavorable and favorable directions. The observed unfavorable changes should be considered in the event of a future lockdown, and should also be monitored to prevent an increase in the nutrition-related burden of disease, should these diet/physical activity changes be maintained in the long run. Understanding the favorable changes may help extend them on a broader scale. This trial was registered at clinicaltrials.gov as NCT03335644.

Background: Since December 2019, the coronavirus disease (COVID-19) has massively spread, with overwhelming of health care systems and numerous deaths worldwide. To remedy this, several countries, including France, have taken strict lockdown measures, requiring the closure of all but essential places. This unprecedented disruption of daily routines has a strong potential for disrupting nutritional behaviours. Nutrition being one of the main modifiable risk factors for chronic disease risk, this may have further consequences for public health. Our objective was therefore to describe nutritional behaviours during the lockdown period and to put them in light of individual characteristics. Methods: 37,252 French adults from the web-based NutriNet-Sante cohort filled lockdown-specific questionnaires in April-May 2020 (nutritional behaviours, body weight, physical activity, 24h-dietary records). Nutritional behaviours were compared before and during lockdown using Student paired t-tests and associated to individual characteristics using multivariable logistic or linear regression models. Clusters of nutritional behaviours were derived from multiple correspondence analysis and ascending hierarchical classification. Results: During the lockdown, trends for unfavourable nutritional behaviours were observed: weight gain (for 35%; +1.8kg on average), decreased physical activity (53%), increased sedentary time (63%), increased snacking, decreased consumption of fresh food products (especially fruit and fish), increased consumption of sweets, biscuits and cakes. Yet, opposite trends were also observed: weight loss (for 23%, -2kg on average), increased home-made cooking (40%), increased physical activity (19%). These behavioural trends related to sociodemographic and economic position, professional situation during the lockdown (teleworking or not), initial weight status, having children at home, anxiety and depressive symptoms, as well as diet quality before the lockdown. Modifications of nutritional practices mainly related to routine change, food supply, emotional reasons but also to voluntary changes to adjust to the current situation. Conclusion: These results suggest that the lockdown led, in a substantial part of the population, to unhealthy nutritional behaviours that, if maintained in the long term, may increase the nutrition-related burden of disease and also impact immunity. Yet, the lockdown situation also created an opportunity for some people to improve their nutritional behaviours, with high stakes to understand the leverages to put these on a long-term footing.