A study published in PLOS Medicine examines the impact of cycling for commuting and recreation on the risk of developing type 2 diabetes. The study done on Danish adults in the age group of 50 and 65 and found that those who reported higher weekly quantities of cycling were less likely to develop diabetes. 
In fact, It was seen that those who took up cycling after the study began also had a lower risk of developing diabetes than those who did not. 

Physical activity has protective effect against morbidity and mortality from cardiovascular disease, diabetes, and some cancers. Public health guidelines highlight the importance of regular activity, recommending at least 30 minutes of moderate-intensity activity on most days of the week for adults, and more for children. However, levels of activity vary between countries, and a sizeable proportion of the global population would benefit from being more active