Abstract Background To contain the COVID-19 pandemic, countries put in place lockdown measures, causing disruption of daily life and changes in lifestyle. Our objective was to explore whether potential changes in diet quality and food supply persisted after the release of lockdown measures, and how these differed according to individual characteristics. Methods The analysis relies on the Geneva (Switzerland) population-based Specchio cohort. In March 2022, an online questionnaire was designed to characterize health behaviors. Nutrition-related changes were assessed through two questions “Today, compared to before the pandemic, would you say that the quality of your diet: • Improved • Improved slightly • Did not change • Deteriorated slightly • Has deteriorated” and “Comparing the current period with that before the pandemic, have you significantly changed your habits regarding your food supply? •Yes •No.” Nutrition-related changes and their determinants were investigated using logistic regression. Results The analysis included 4065 participants (response rate 46%). Mean age was 54 years, 59% were women. 17% of participants reported that their diet had improved or slightly improved compared to before the pandemic. Our results showed a clear age gradient, with younger participants having higher odds of reporting an improved diet (aOR 0.98 (0.97-0.98) per year, p < 0.001). Participants who reported not paying attention to their health did not report an improved diet (aOR 0.29 (0.16-0.49), p < 0.001); those who reported significant changes in their food supply habits had greater odds of reporting they improved their diet (aOR 3.37 (2.76-4.11), p < 0.001). The most popular changes were going more frequently to markets or to small shops. We found no significant differences by sex or by education. Conclusions As reported from other countries, our results showed improved diet quality compared to before the pandemic in certain population subgroups, mainly due to changes in local food supply. Key messages • Favorable changes in diet quality and food supply during the Covid-19 pandemic were observed in certain population subgroups. • With health behavior changes due to pandemic, including nutrition, digital population-based cohorts such as Specchio become a rich resource to produce novel and timely evidence over time.