OBJECTIVES: To provide baseline cohort descriptives and assess change in health behaviours since the UK COVID-19 lockdown.

DESIGN: A prospective cohort (N = 1,044) of people recruited online, purposively targeting vulnerable populations.

METHODS: After a baseline survey (April 2020), participants completed 3 months of daily ecological momentary assessments (EMA). Dietary, physical activity, alcohol, smoking, vaping and substance use behaviours collected retrospectively for the pre-COVID-19 period were compared with daily EMA surveys over the first 30 days during early lockdown. Predictors of behaviour change were assessed using multivariable regression models.

RESULTS: 30% of the cohort had a COVID-19 at risk health condition, 37% were classed as deprived and 6% self-reported a mental health condition. Relative to pre-pandemic levels, participants ate almost one portion of fruit and vegetables less per day (vegetables mean difference -0.33, 95% CI -0.40, -0.25; fruit -0.57, 95% CI -0.64, -0.50), but showed no change in high sugar portions per day (-0.03, 95% CI -0.12, 0.06). Participants spent half a day less per week doing ≥30 min of moderate to vigorous physical activity (-0.57, 95% CI -0.73, -0.40) but slightly increased days of strength training (0.21, 95% CI 0.09, 0.34), increased alcohol intake (AUDIT-C score change 0.25, 95% CI 0.13, 0.37), though did not change smoking, vaping or substance use behaviour. Worsening health behaviour change was associated with being younger, female and higher body mass index.

CONCLUSIONS: The cohort reported worsening health behaviours during early lockdown. Longer term changes will be investigated using further waves of data collection.