PurposeCOVID-19 lockdown changed social habits and lifestyle, including dietary habits, of people worldwide. However, limited information is available about these changes in Egypt. This cross-sectional study investigates the effects of COVID-19 lockdown on dietary habits among the Egyptian populations.MethodsAn online questionnaire, based on sociodemographic data and dietary adherence in accordance with the validated PREDIMED MedDiet Adherence Screener (MEDAS), was used all over the Egyptian governorates. The dietary changes were statistically evaluated for significance in relation to age, gender, body mass index (BMI), education level and governorates.ResultsA total of 1010 participants (76% aged below 36 years, 77% female, 22% obese, and 62% university-level education) answered the questionnaire. Respondents ≤ 20 years had a significant increase in weight and consumption of carbonated beverages, commercial pastries, fried and fast food. Egyptians > 50 years old had a significant decrease in physical activity. Underweight people (less than 3% of participants) increased their fast food intake with a prominent rise in weight. However, obese people increased cooking frequency and increased eating times with a decrease in physical activity. Male participants reported increased intake of carbonated beverages and fast food, while female participants increased the intake of homemade pastries with a significant decrease in physical activity. Approximately 50% of participants with postgraduate education reported decreased intake of fast food and carbonated beverages as well as decreased body weight. Residents of Cairo showed a significant increase in vegetable intake, and fried food intake with a decrease in seafood consumption. Participants from the Delta region had a significant increase in pastries intake.ConclusionThe findings of this study explored the need for increasing awareness about healthy lifestyle in future lockdown periods.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12889-023-15777-7.