Artificially sweetened beverages like Diet Coke are often considered healthier alternatives, but the debate over their impact on obesity persists. Previous research has predominantly relied on observational data or randomized controlled trials (RCTs), which may not accurately capture the causal relationship between Diet Coke consumption and obesity. This study uses causal inference methods, employing data from the National Health and Nutrition Examination Survey (NHANES) to examine this relationship across diverse demographics. Instead of relying on RCT data, we constructed a causal graph and applied the back-door criterion with its adjustment formula to estimate the RCT distributions. We then calculated the counterfactual quantity, the Probability of Necessity and Sufficiency (PNS), using both NHANES data and estimated RCT data. We propose that PNS is the essential metric for assessing the impact of Diet Coke on obesity. Our results indicate that between 20% to 50% of individuals, especially those with poor dietary habits, are more likely to gain weight from Diet Coke. Conversely, in groups like young females with healthier diets, only a small proportion experience weight gain due to Diet Coke. These findings highlight the influence of individual lifestyle and potential hormonal factors on the varied effects of Diet Coke, providing a new framework for understanding its nutritional impacts on health.

使用因果推断方法和全国健康和营养调查（NHANES）数据，这项研究提出了概率的必要性和充分性（PNS）作为评估饮用健怡可乐对肥胖的影响的关键指标，结果显示约20%至50%的人，尤其是饮食习惯不良者，更容易因健怡可乐增加体重；而对于像年轻女性这样饮食健康的群体，只有少部分人因饮用健怡可乐而增重，这突显了个体生活方式和潜在的激素因素对健怡可乐的不同影响，为理解其对健康的营养影响提供了新的框架。

罐中的因果关系：饮用健怡可乐对肥胖的影响