BACKGROUND: COVID-19 lockdowns were linked to a surge in unhealthy food-related behaviors, potentially as an attempt to cope with disrupted social homeostasis. Here, we tested bidirectional associations between momentary psychological states and prospective food consumption, and the moderation by quality and quantity of social interactions. METHODS: We conducted a preregistered ecological momentary assessment (EMA) study in Austria, Italy and Germany during the first COVID-19 lockdown. Multiple times a day for seven consecutive days, 798 participants (557 women, M RESULTS: Momentary stress was positively linked to food wanting, but not prospective food consumption. Mood valence and energetic arousal positively predicted prospective food consumption and enjoyment. The effect of mood valence was especially prominent when participants reported having more social interactions. Food consumption was linked to a prospective reduction in stress and an increase in calmness, suggesting it has regulatory functions for affective states. Exploratory findings show that some of these effects generalize to other reward types. CONCLUSIONS: During the lockdown, food may have been used to maintain an already positive affective state rather than upregulating an aversive state. Social facilitation of eating may have been especially prominent due to the prioritization of our social needs at the start of an extraordinarily challenging period, possibly orchestrated by the postulated social homeostasis system.