Distilling causality between physical activity traits and obesity via Mendelian randomization

Area of Science:

• Genetics
• Public Health
• Epidemiology

Background:

• The causal relationship between physical activity, sedentary behavior, and obesity remains unclear.
• Confounding variables and robust instrumental variables are crucial for accurate causal inference.

Purpose of the Study:

• To investigate the causal links between physical activity, sedentary behavior, education, and body mass index (BMI).
• To utilize Mendelian Randomization (MR) to disentangle these complex relationships.

Main Methods:

• Employed univariable and multivariable Mendelian Randomization (MR) approaches.
• Leveraged genome-wide association study data for physical activity and screen time.
• Incorporated education (years of schooling) as a key variable in multivariable analyses.

Main Results:

• Univariable MR indicated bidirectional effects between physical activity, sedentary behavior, and BMI.
• Multivariable MR revealed that increased moderate-to-vigorous (MV) physical activity reduces BMI.
• Higher BMI was associated with increased screen time, while education positively influenced MV physical activity and negatively impacted screen time and BMI.

Conclusions:

• Education positively influences health outcomes, including increased physical activity and reduced BMI.
• A physically active lifestyle is causally linked to lower BMI.
• Sedentary behavior, specifically screen time, appears to be a consequence of higher BMI.