Abstract
Background: When a person’s body mass index (BMI) is above the normal range but below the threshold for obesity, he or she is termed as overweight (BMI = 25–29.9 kg/m2). Recently, the incidence of myocardial infarction has greatly increased among the young adults. This is mainly due to stress, sedentary lifestyle, and increased intake of junk foods. Reduced heart rate variability (HRV) is a sign of poor cardiac autonomic function. Obese individuals are known to have reduced HRV. However, there are not many studies that have explored the changes in HRV indices among the overweight individuals.

Aims and Objective: To find out the influence of higher BMI on HRV in overweight young adult men.

Materials and Methods: Eighteen men (30 ± 4 years, mean ± SD) with BMI in the overweight range (test group) and 18 age-matched men with normal BMI (control group) were included in the study. Five-minute ECG was recorded in lead II configuration in all the subjects following 10 min of rest in supine posture. HRV parameters (time domain and frequency domain) were derived from the ECG. The HRV parameters of the test and the control group were compared using Mann–Whitney U-test. A p-value of <0.05 was considered significant.

Result: Overweight individuals had a significantly high mean heart rate (p = 0.029) and a significantly low RMSSD (root mean square of successive differences) (p = 0.035) and high-frequency (HF) normalized units (nu) values (p = 0.049) indicative of decreased parasympathetic activity. Low-frequency (LF) nu (p = 0.069) and LF/HF ratio (p = 0.082) values were higher in the test group, but not significant. SDNN (standard deviation of the NN intervals), a measure of total HRV, was also significantly low in the test group (p = 0.019).

Conclusion: Apparently healthy overweight men have reduced HRV, which may lead to increased cardiovascular morbidity and mortality in these individuals. Hence, emphasis must be placed on early adoption of lifestyle modifications to prevent the progress of impending alterations in cardiovascular status of these young adults.

Key words: Overweight Young Males; Heart Rate Variability; Autonomic Functions; Time Domain Analysis; Frequency Domain Analysis