Impact of the first COVID-19 lockdown on body weight: A combined systematic review and a meta-analysis.

The coronavirus disease 2019 (COVID-19) and the imposed lockdowns in order to control the pandemic, had undoubtedly influenced the lifestyle of millions of people worldwide. The period of confinement, which was characterized by seizing most business activities and allowing only for e-classes at schools and universities, leading also to a lower physical activity, could have affected eating behaviors of people of all ages. In this study we aimed to investigate the impact of the first lockdown period (March-May 2020) on body weight (BW) and on body mass index (BMI) in both adults and adolescents (>16 years old). A systematic literature search was conducted in PubMed®, Scopus®, Web of Science® and EMBASE® databases and 36 observational (35 cross-sectional and one cohort) studies were included. BW and BMI changes after/during the lockdown period were examined. BW was stated as increased in a significant part of the individuals (11.1-72.4%), although a range of 7.2-51.4% of individuals reported weight loss. A significant higher BW was observed with a weighted mean between-group difference (WMD) 1.57 (95% CI 1.01 to 2.14) in the post-lockdown period compared to the before lockdown time and higher BMI, 0.31 WMD (95% CI, 0.17 to 0.45) was identified before the lockdown period. At variance with general trends, one study in older adults (>60 years old) notably reported a significant BW loss, suggesting a higher risk for lockdown-induced weight loss and potentially malnutrition in the elderly population. Overall increments in BW are an alarming effect of lockdown during the COVID-19 pandemic, leading to potential higher incidence of overweight, obesity and related health-risks as well as other noncommunicable diseases. Further studies are needed to assess potential group-specific impacts, with particular regard to weight gain in younger people and risk of weight loss, malnutrition and sarcopenia in older adults.