Purpose: To evaluate whether excess body mass influences the heart rate variability (HRV) indexes at rest, and to correlate adiposity indicators and the aerobic fitness with cardiac autonomic variables in metabolically healthy young adults. Method: In all, 41 untrained males (M[subscript age] = 21.80, SD = 2.14 years), 14 normal weight (M[subscript BMI] = 22.28, SD = 1.86 kg·m[superscript-2]), 11 overweight (M[subscript BMI] = 26.95, SD = 1.43 kg·m[superscript-2]), and 16 obese (M[subscript BMI] = 33.58, SD = 3.06 kg·m[superscript -2]) metabolically healthy (normal values of blood pressure, fasting blood glucose, triglycerides, and total cholesterol), underwent evaluations of the HRV at rest and of the peak oxygen consumption (VO[subscript 2] peak) during maximal exercise on a cycle ergometer. Results: Blood pressure, heart rate, HRV indexes, casual blood glucose, oxidative stress, and antioxidant activity did not differ among the groups. The VO[subscript 2] peak (mL·kg[superscript -1]·min[superscript-1]) was lower in the obese group compared with the normal weight and overweight groups. The body mass (r = -.40 to -.45) and abdominal circumference (r = -0.39 to -0.52) were slightly to moderately correlated with SD1, SD2, RMSSD, SDNN, pNN50, LF, and HF indexes and total power. The VO[subscript 2] peak (mL·kg[superscript -1]·min[superscript -1]) was slightly to moderately correlated (r = 0.48 to 0.51) with SD2, SDNN, and LF indexes in the individuals with excess body mass. Conclusion: Cardiac autonomic modulation at rest was preserved in metabolically healthy obese young men. However, the indicators of adiposity, as well as the aerobic fitness were correlated with cardiac autonomic modulation in the individuals with excess body mass.