Abstract
The combined impact of physical activity (PA), diet quality, and their change over time on cardiometabolic disease risk remains uncertain. We aimed to examine the associations between the combined trajectories of these health behaviours and the incidence of diabetes mellitus (DM) and cardiovascular diseases (CVD) among 9,276 middle-aged adults. In the EPIC-Norfolk study, longitudinal changes in PA energy expenditure (∆PAEE) and Mediterranean diet score (∆MDS) were derived from repeated measurements between 1993 and 2004. Over a median follow-up of 18 years, 968 participants developed DM and 2,540 developed CVD by 2022. In mutually adjusted Cox regression models, HR (95%CI) per 1-SD higher ∆PAEE and ∆MDS were 0.87 (0.81-0.94) and 0.92 (0.86-0.99) for incident DM, and 0.94 (0.89-0.99) and 0.93 (0.88-0.97) for incident CVD, respectively. Compared to participants with sustained low PAEE and MDS, those with sustained higher levels of both traits had a 40% (21-55%) lower incidence of DM and a 25% (11-37%) lower CVD incidence. At the population level, consistent favourable levels of activity and diet quality could reduce cumulative incidence of DM by 22% and CVD by 16%. The greatest benefit arises when an active lifestyle is combined with a high-quality diet, initiated earlier in adulthood, and maintained over time.