Background:The aims of the present study were to assess changes in lifestyles in thegeneral population in response to coronavirus disease 2019 (COVID-19) lockdown andthe influence of COVID-19 perceptions, as assessed by the Extended Parallel ProcessModel (EPPM), on these changes.Methods:Data were collected from 4005 individuals through an online surveyconducted 3–4 weeks after the nationwide lockdown implementation in France.Participants were asked whether they practiced five behaviors (i.e., screen watching,snacking, eating fruits and vegetables, exercising, and walking) less often, as often as,or more often than prior to the lockdown. Beliefs and expectations toward the COVID-19epidemic were also assessed using an adapted version of Witte’s EPPM, together withsociodemographic and environmental variables. Among the respondents consumingregularly alcohol and tobacco, logistic regressions were performed to estimate the Oddsratios (ORs) of increase (yes/no) and decrease (yes/no) in drinking and smoking sincethe lockdown.Results:More than 8 in 10 respondents reported unhealthy changes in lifestyle sincethe lockdown, mostly in relation to physical activity. The unhealthy changes werepositively associated with male sex (RR = 1.17; confidence interval [95% CI] = 1.10–1.24), living urban density, having a garden (RR = 1.16 [1.07–1.26]), financial difficultiesbecause of COVID-19 (RR = 1.09 [1.02–1.18]), and lack of fear control (RR = 1.04[1.01–1.09]) and negatively with cognitive avoidance (RR = 0.92 [0.89–0.95]). Less than4 in 10 respondents reported healthy changes over the same period, mostly in relationto better eating habits. They were positively associated with living with more than twopersons (RR = 1.22 [1.02–1.45]), having a terrace (RR = 1.14 [1.02–1.29], and perceivedefficacy (RR = 1.11 [1.04–1.08]) and negatively with being aged 40 or higher. Alcoholconsumption overall declined in regular drinkers, while a slight increase in tobacco usewas observed in regular smokers.Discussion:The COVID-19 pandemic and lockdown resulted in frequent and mostlyunhealthy changes in lifestyle among the general population. These changes were related to individual and environmental characteristics but also to EPPM appraisals inthe wake of fear appeal from COVID-19 campaigns. Communication and preventivemeasures should include messages and initiatives toward the maintenance of healthylifestyles during pandemics such as the adaptation of physical activity and eatingguidelines to the particular contexts of mobility restriction and infection control.