Less Sitting for Preventing Type 2 Diabetes.

The findings reported by Li et al. (1) in this issue of Diabetes Care are a welcome contribution to the body of evidence informing type 2 diabetes prevention. They focus on sedentary behavior (put simply, too much sitting), which has adverse health consequences that are distinct from those of too little exercise (2). These new findings, from a prospective study with long-term follow-up of 475,502 adults with 18,619 type 2 diabetes cases, represent strong evidence pointing to causality in the relationships of sedentary behavior with the development of type 2 diabetes. To this end, the study by Li et al. has strengths of method and analytical approach, employing measures of both physical activity and sedentary behavior as exposures, and examining their interrelationships as predictors of the diagnosis of type 2 diabetes over an 11-year median follow-up interval. Importantly, their analyses used iso-temporal substitution methods, which allow statistical estimation of the benefits of reallocating time in one behavior for time in another behavior. Although iso-temporal substitution has previously been used to model the putative impacts of substituting physical activity for sedentary time, such evidence has come predominantly from cross-sectional studies (3). Sedentary behaviors—primarily television (TV) viewing and other screen use, time sitting in cars, and desk-based working—occupy the largest proportion of adults’ waking hours. Over the past 10 years, sedentary time, characterized by a sitting posture in the absence of skeletal muscle contractile activity (4,5), has increased by ∼1 h/day (6). The coronavirus disease 2019 pandemic has further exacerbated the pervasiveness of prolonged periods of time spent sitting in people’s lives (7). The widespread implementation of infection-risk mitigation strategies has seen daily time spent sitting increase by a staggering 3 h/day (8). Because sedentary behavior displaces time spent engaging in …