The aim was to identify the main consequences of COVID-19 lockdown on Body Mass Index and Perceived Fragility, related to Physical Activity (PA), for different categories of populations, worldwide. Design: The study design included an online survey, during the first wave of COVID-19 lockdown, across different world regions. Setting and participants: The research was carried out on 10 121 participants from 67 countries. The recruitment of participants was achieved using snowball sampling techniques via social networks, with no exclusion criteria other than social media access. Main outcome measures: Body Mass Index, Physical Activity, Perceived Fragility and risk of getting infected items were analysed. SPSS software, v20, was used. Significance was set at P < .05. Results: Body Mass Index significantly increased during lockdown. For youth and young adults (18-35 years), PA decreased by 31.25%, for adults (36-65 years) by 26.05% and for the elderly (over 65 years) by 30.27%. There was a high level of Perceived Fragility and risk of getting infected for female participants and the elderly. Correlations between BMI, Perceived Fragility and PA were identified.