Causal relationship between dietary macronutrient composition and anthropometric measures: A bidirectional two-sample...

Area of Science:

• Nutritional Epidemiology
• Genetic Epidemiology
• Public Health

Background:

• Investigating the link between dietary macronutrient proportions and anthropometric measures like BMI and WC is crucial for public health.
• Establishing causality is challenging in traditional epidemiological studies due to confounding factors.

Purpose of the Study:

• To determine the causal relationship between the relative proportions of dietary macronutrients (carbohydrates, fat, protein) and body mass index (BMI) and waist circumference (WC) using Mendelian randomization.
• To explore the reverse causality: whether BMI and WC influence macronutrient intake proportions.

Main Methods:

• A two-sample bidirectional Mendelian randomization (MR) analysis was conducted using large-scale genome-wide association study data.
• Data included genetic associations for dietary intake (SSGAC Consortium) and anthropometric measures (GIANT Consortium) from European populations.
• Sensitivity analyses employed methods like MR-Egger, weighted median, and Robust Adjusted Profile Score (RAPS) to ensure robustness of findings.

Main Results:

• Genetically predicted higher relative carbohydrate intake was causally associated with lower BMI and WC.
• Genetically predicted higher relative fat intake showed a weaker, positive association with BMI and WC.
• Evidence suggested that higher BMI and WC causally influenced increased relative intake of fat and protein.

Conclusions:

• Dietary composition, specifically a lower proportion of carbohydrates and a higher proportion of fat, is causally associated with increased BMI and WC.
• These findings highlight the importance of macronutrient balance in weight management.
• Further research is needed to explore the quality of macronutrients and their impact on micronutrient intake for refined dietary recommendations.