Aims  To describe change in physical activity over 1 year and associations with change in cardiovascular disease risk factors in a population with screen‐detected Type 2 diabetes.

Methods  Eight hundred and sixty‐seven individuals with screen‐detected diabetes underwent measurement of self‐reported physical activity, cardiovascular disease risk factors and modelled cardiovascular disease risk at baseline and 1 year (n = 736) in the ADDITION‐Cambridge trial. Multiple linear regression was used to quantify the association between change in different physical activity domains and cardiovascular disease risk factors at 1 year.

Results  There was no change in self‐reported physical activity over 12 months. Even relatively large changes in physical activity were associated with relatively small changes in cardiovascular disease risk factors after allowing for changes in self‐reported medication and diet. For every 30 metabolic equivalent‐h increase in recreational activity (equivalent to 10 h/brisk walking/week), there was an average reduction of 0.1% in HbA1c in men (95% CI −0.15 to −0.01, P = 0.021) and an average reduction of 2 mmHg in systolic blood pressure in women (95% CI −4.0 to −0.05, P = 0.045).

Conclusions  Few associations were observed between change in different physical activity domains and cardiovascular disease risk factors in this trial cohort. Cardiovascular disease risk reduction appeared to be driven largely by factors other than changes in self‐reported physical activity in the first year following diagnosis.