Introduction and objective:
The disruption of daily activities caused by the COVID-19 pandemic had health consequences, especially during peak lockdown periods. The aim of the study is to assess the impact of the first year of the COVID-19 pandemic on the process of weight change among Polish adults.

Material and methods:
Two representative studies involving Polish adults aged 18–65 years were conducted, the first in June 2020 (N = 2527, from the perspective of the last 2–3 months), and the second a year later, in June 2021 (N = 2087, covering the last 12 months). Both surveys included two groups of respondents, and conducted using the CAWI method – computer-assisted web interview.

Results:
In the first period of the COVID-19 pandemic, there were more individuals with obesity than a year later (18.7% vs 19.9%), and more respondents reported weight change in 2020 than in 2021 (53% vs 49.6%). In both surveys, women were more likely to report weight gain than men (p<0.001). Statistically significant factors for weight change in 2020 and 2021 were gender, age, and in 2021, education and relationship status. Multinomial logistic regression showed that BMI, age of 18–29 and 30–49, being male, and education below high school, was significant for weight gain. While for weight loss, BMI, age 18–29 and 30–49, being male, and year of study, were statistically significant.

Conclusions:
The findings confirmed that body weight changed throughout the pandemic, depending on the time of the pandemic and selected socio-demographic factors.