title: Impact of diet-induced weight loss on the cardiac autonomic nervous system in severe obesity.
abstract: OBJECTIVE
  To determine the impact of diet-induced weight loss on cardiac autonomic nervous system modulation and arrhythmias in subjects with severe obesity and the influence of a high-fat or a high-carbohydrate diet regimen on heart rate variability in reduced-obese individuals.
  
  
  METHODS
  Eight severely obese subjects (BMI > or = 40.0 kg/m(2)) underwent a 3-month weight loss program followed by a 3-month reduced-weight maintenance regimen. Thereafter, each subject was admitted for an inpatient period of 17 days on two separate occasions. A high-carbohydrate (60%) or high-fat (55%) diet of appropriate energy content for weight maintenance was prescribed during each inpatient phase. Heart rate variability was derived from a 24-hour Holter monitoring system in all subjects during their inpatient stay. Cardiac Holter monitoring was performed at three occasions (baseline, diet phase I, and diet phase II), including the second night of a two overnight calorimetry chamber stay.
  
  
  RESULTS
  After the diet regimen, there was a 10% decrease in weight. There were no significant changes in systolic and diastolic blood pressure, arrhythmias, glucose, insulin, total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, respiratory exchange ratio, and resting energy expenditure between experiments. Mean heart rate was lower after weight loss compared with baseline (p < 0.001). After weight loss, there was an increase in the parasympathetic indices of heart rate variability showing an increase in cardiac vagal modulation (all p < 0.05).
  
  
  CONCLUSIONS
  Weight loss is associated with significant improvement in autonomic cardiac modulation through enhancement of parasympathetic modulation, which clinically translates into a decrease in heart rate.
authors.affiliation: Division of Endocrinology, Metabolism, and Diabetes, University of Colorado Health Sciences Center, Denver, Colorado, USA. Paul.Poirier@crhl.ulaval.ca
authors.forename: Paul
authors.initials: P
authors.lastname: Poirier
authors.forename: Teri L
authors.initials: TL
authors.lastname: Hernandez
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Weil
authors.forename: Trudy J
authors.initials: TJ
authors.lastname: Shepard
authors.forename: Robert H
authors.initials: RH
authors.lastname: Eckel
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D001481:Basal Metabolism / Q000502:physiology; D002153:Calorimetry, Indirect; D018592:Cross-Over Studies; D004038:Diet, Reducing / Q000379:methods; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism; D015716:Electrocardiography, Ambulatory; D004734:Energy Metabolism; D005260:Female; D006321:Heart / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D009767:Obesity, Morbid / Q000178:diet therapy* / Q000503:physiopathology*; D015431:Weight Loss / Q000502:physiology*
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats