The purpose of this study was to assess impact of different volumes of exercise as well as cumulative moderate to vigorous physical activity (MVPA) on energy intake (EI) and diet quality, as assessed by the Healthy Eating Index-2010(HEI-2010), across a 12-month weight maintenance intervention. Participants were asked to attend group behavioural sessions, eat a diet designed for weight maintenance and exercise either 150, 225 or 300 min/week. Dietary intake was assessed by 3-d food records, and MVPA was assessed by accelerometry. Two hundred and twenty-four participants (42·5 years of age, 82 % female) provided valid dietary data for at least one time point. There was no evidence of group differences in EI, total HEI-2010 score or any of the HEI-2010 component scores (all P > 0·05). After adjusting for age, sex, time, group and group-by-time interactions, there was an effect of cumulative MVPA on EI (1·08, P = 0·04), total HEI-2010 scores (–0·02, P = 0·003), Na (–0·006, P = 0·002) and empty energy scores (–0·007, P = 0·004. There was evidence of a small relationship between cumulative daily EI and weight (β: 0·00187, 95 % CI 0·001, P = 0·003). However, there was no evidence for a relationship between HEI total score (β: −0·006, 95 % CI 0·07, 0·06) or component scores (all P > 0·05) and change in weight across time. The results of this study suggest that increased cumulative MVPA is associated with clinically insignificant increases in EI and decreases in HEI.