[Changes in autonomic nervous system activity in obese individuals during weight reduction]

The frequency analysis (fast Fourier transformation) of heart rate variability follow-up during modified orthostatic test is the non-invasive method used to the evaluation of vegetative nervous system (NS) activity. There are only few data about the changes of the parameters in the groups with civilization diseases or with the presence of the risk factors of coronary heart disease. In the groups of 82 volunteers (BMI 24.9 +/- 2.7 kg/m2) and 37 healthy obese people (BMI 36.1 +/- 4.9 kg/m2) we compare some of the vegetative NS parameters. In 16 volunteers we measured the vegetative NS activity changes during the weight reduction regimen (10 day's hospitalization, daily energy intake 3300 kJ, weight before 101.5 +/- 18.1 kg, after 97.5 +/- 17.1 kg, p < 0.0001). Acute reactions to the energy restriction were evaluated in 3 groups of 10 volunteers during 3 days of the energy intake 3200, 6600 and 13400 kJ. Obese persons show a slight decrease of both sympathetic and parasympathetic NS activity. In the supine position only few changes in the sympathetic/parasympathetic NS activity ration were observed. In the standing position in obese group drop of the most indexes and decrease of sympathetic/parasympathetic NS activity ratio were described. Significant correlations between sympathetic NS activity and lipid oxidation (r = 0.329, p < 0.01) as well as saccharide oxidation (r = -0.258, p < 0.05) were observed. During the weight reduction slight increase of the parasympathetic NS activity and higher one in the sympathetic NS activity were measured. The values after weight reduction regime are comparable with the control group of the lean persons. Different changes of the parameters were described in standing and in supine position. Acute reaction on the low-energy diet was observed in a few days. It shows a slight increase of the NS activity parameters. Relative increase mainly in the sympathetic nervous system activity doesn't depend on the degree of energy deficit only, but some subjective factors may play a role (age, psychological and psychosocial factors, agreeability of the diet, behavioral factors ...). In the group of obese persons non-specific changes of the vegetative NS activity were observed. They are modulated by some behavioral factors. The tendency to the higher parasympathetic NS activity confirms the MONA LISA theory of the origin of obesity. Important are the informations of the return of the indexes after overweight reduction.