Despite evidence linking obesity with increased mortality, older adults with excessive adiposity seem protected, resulting in a so-called obesity paradox. Obesity is characterized by leptin resistance, which contributes to increased risk of all-cause mortality. Therefore, lifestyle factors, such as physical fitness, that lower leptin independent of adiposity may be confounding the obesity paradox. To investigate this, we evaluated whether physical fitness moderated the relationship between leptin and adiposity. We found older adults with higher fitness had lower body mass (r(39) = -0.43, p < 0.01), leptin (r(39) = -0.29, p = 0.03) and inflammation (IL-1β: (r(39) = -0.69, p < 0.01); TNF-α: (r(39) = -0.30, p = 0.03)). Fitness moderated the relationship between leptin and adiposity (F(5, 37) = 3.73, p < 0.01, R² = 0.33) to reveal the obesity paradox in moderately and high fit individuals (b = 216.24, t(37) = 1.46, p = 0.15; b= -88.10, t(37) = -0.49, p = 0.63) but not in low fit individuals. These results show the link between obesity and mortality may not be dependent on total adiposity, but rather on endocrine function and adipocyte leptin secretion. These results have important implications for older adults struggling to maintain healthy body composition and suggest that fitness may promote overall wellbeing.

尽管有证据表明肥胖与死亡率增加有关，但过度肥胖的老年人似乎受到了保护，从而导致了所谓的肥胖悖论。肥胖的特征是瘦素抵抗，这会增加全因死亡的风险。因此，生活方式因素，如身体健康，降低瘦素与肥胖无关，可能会混淆肥胖悖论。为了研究这一点，我们评估了身体健康是否调节了瘦素和肥胖之间的关系。我们发现身体素质较高的老年人体重较低（r (39) = -0.43, p < 0.01）、瘦素（r (39) = -0.29, p = 0.03）和炎症 (IL-1 β : ( r ( 39) = -0.69,p < 0.01); TNF-α：（r (39) = -0.30，p = 0.03)）。健身调节了瘦素和肥胖之间的关系（F (5, 37) = 3.73, p < 0.01, R ² = 0.33），以揭示中等和高度健康个体的肥胖悖论（b = 216.24, t (37) = 1.46, p = 0.15; b = -88.10, t (37) = -0.49, p= 0.63) 但不适用于低健康个体。这些结果表明肥胖和死亡率之间的联系可能不取决于总肥胖，而是取决于内分泌功能和脂肪细胞瘦素分泌。这些结果对努力保持健康身体成分的老年人具有重要意义，并表明健身可以促进整体健康。