Exercising in the late-afternoon or evening was found to reduce the risk for cardiovascular disease, microvascular disease, and all-cause mortality in adults with obesity, according to the results of a new study. 

Published in Diabetes Care, the study classified 29,836 participants with a BMI of 30 kg/m2 or higher into morning, afternoon, or evening groups based on when they engaged in most of their moderate to vigorous physical activity. Specifically, evening MVPA participants showed a hazard ratio (HR) of 0.39 for mortality risk, significantly lower than those exercising in the morning (HR 0.67) or afternoon (HR 0.60). 

The mechanisms underlying these associations may relate to the body's circadian rhythms and the timing of metabolic processes. For individuals with obesity and T2D, evening may be an optimal time for engaging in physical activity to counteract the diurnal variations in glucose tolerance and insulin sensitivity, according to the study investigators. This aligns with previous clinical studies suggesting that late-afternoon or evening exercise yields superior improvements in metabolic health compared with morning activity. 

These results suggest adjusting exercise schedules could significantly enhance health outcomes, the investigators noted. However, it is important to note that while evening activity was most beneficial, any aerobic MVPA, regardless of timing, contributed to better health outcomes compared with no aerobic activity. 

"This study, to our knowledge, is the first to determine the associations between objectively measured aerobic MVPA timing, all-cause mortality, and incidence of CVD and MVD in adults with obesity. These findings demonstrate a compelling connection between MVPA timing and a lower risk of morbidity and mortality in adults with obesity, including those with T2D," the investigators wrote. Further research is needed to fully understand the implications and to explore whether these findings can be generalized to different populations or those with other conditions. 

The authors declared no conflicts of interest. The study was supported by funding from the National Heart Foundation of Australia and an Australian National Health and Medical Research Council Investigator Grant.