The present study was focused on identifying and analyzing the variations in lifestyles and dietary behaviors of Sri Lankans during a critical period of the COVID-19 pandemic. Self-administered questionnaires were formulated in Sinhala and English languages, distributed following the snowball sampling method and the collected data were analyzed statistically. The respondents varied in age from 16 to 85 years and the majority were females. The majority of the respondents concerned about their diet and the concern varied among the respondents irrespective of the changes in their income during the pandemic. Among the respondents those who declared either an increased or decreased appetite, the majority were females. The majority in the 16 to 20 years age group declared an increased appetite and the majority of other age groups declared no changes. The majority of the respondents declared a decrease in consuming bread, short-eats, sweets and cold or frozen foods and an increase in drinking hot water and hot beverages. The changes in body weight were associated with the changes in appetite, the number of times they felt hungry in a day and the variations in stress, anxiety and depression. Happiness and peacefulness, stress, anxiety and depression varied among the respondents regardless of their living conditions. Sleeping patterns of more than half of the respondents changed during the confinement. The variations in daily routine indicated the influence of the confinement towards a more sedentary lifestyle. A considerable percentage of the respondents declared an increase in the time spent on reading books and home gardening. The majority of the respondents were aware of the protective measures required to prevent the adverse outcomes of the pandemic. The decrease in fast-food consumption and the increase in the time spent on home gardening can be considered as the positive effects of the confinement.