Oxidative stress and mitochondrial function measurements in human sperm. (A) Mean fluorescence intensity of Liperfluo (lipid peroxidation) and (B) si‐DMA (mitochondrial singlet oxygen) of human sperm from normal weight and overweight/obese groups (n = 15). (C) SOD activity was measured in human seminal plasma (n = 15). (D) Comparisons of the JC‐1 red/green fluorescence ratio in sperm between the two groups indicated mitochondrial membrane potential (n = 15). (E) Negative correlation between ATP content in human sperm and BMI values (n = 40). (F) Analysis of sperm quality via detecting the percentages of grade a, b, c, and d sperm, and (G) comparison of sperm motility between normal weight and overweight/obese subjects (n = 46 in normal weight group, n = 69 in overweight/obese group). Data are expressed as mean ± SD or percentage (%). Statistical analyses were performed using the Student's t‐test (A–D, F, and G) and Pearson correlation coefficient (E). *P < 0.05, **P < 0.01, ***P < 0.001. Grade a: linear motion; Grade b: slow motion; Grade c: in‐situ motion; Grade d: no motion. Motility (%) = grade a (%) + grade b (%).