Is Being Physically Active Enough to Be Metabolically Healthy? The Key Role of Sedentary Behavior.

Low levels of physical activity (PA) are now well recognized as a major public health problem, implicated in cancer, cardiovascular disease (CVD), metabolic syndrome, diabetes, and early mortality (1). PA guidelines (i.e., ≥150 min/week of moderate activity or ≥75 min/week of vigorous activity, collectively referred to as moderate to vigorous physical activity [MVPA]) are globally promoted to protect the population against the risk of developing chronic disease. But is this sufficient to promote metabolic health? The relationship between PA and health appears to be more complex than initially thought, and another component has been attracting attention over the past decade: sedentary behavior (SB). Although they are often used interchangeably, SB is fundamentally different from physical inactivity. While physical inactivity is defined as engaging in less PA than necessary to meet the current guidelines (2), SB describes “any waking behavior characterized by an energy expenditure ≤1.5 metabolic equivalents (METs) while in a sitting or reclining posture” (3). Thus, individuals can be both physically active and highly sedentary (4,5). Increased time spent sitting raises the risk for metabolic syndrome (6), incident CVD, CVD-related risk factors, and early mortality (7,8), even in people who exercise regularly. These observations raise obvious questions: Are the effects of SB independent from those of PA or simply the “other side of the coin”? What is the minimum level of MVPA needed to counteract the adverse health effects of SB? A recent harmonized meta-analysis of data from more than 1 million adults showed that high levels of PA (i.e., about 60–75 min/day of MVPA) are needed to eliminate the effect of 9 h/day of SB on mortality (9). Even if this exceeds the current PA …