Resting energy expenditure, cardiovascular risk factors and insulin resistance in obese patients

OBJECTIVE: The aim of our study was to determine whether energy expenditure modified by increasing body mass over the wide range of body mass index (BMI) was related to insulin resistance, cardiovascular risk factors and dietary intakes. SUBJECTS AND METHODS: A population of 87 obese non-diabetic outpatients was analyzed prospectively. Indirect calorimetry, tetrapolar electrical bioimpedance, serial assessment of nutritional intake using written 3-day food records and biochemical analyses were performed. RESULTS: The mean age was 45.1 +/- 16.7 years and the mean BMI was 35.2 +/- 5.2. Indirect calorimetry showed a resting metabolic rate (RMR) of 1,732.2 +/- 406.6 kcal/day and oxygen consumption of 266.2 +/- 63.3 ml/min. RMR corrected by fat-free mass was 36.8 +/- 14.1 kcal/day/kg. Serial assessment of nutritional intake using written 3-day food records showed a calorie intake of 1,660 +/- 551.7 cal/day, a carbohydrate intake of 168.63 +/- 76.6 g/day, a fat intake of 72.1 +/- 26.42 g/day and a protein intake of 81.1 +/- 23.3 g/day. Insulin, HOMA, systolic blood pressure, diastolic blood pressure, waist circumference, fat mass, waist-to-hip ratio were higher in the third BMI tertile than in the first and second tertiles. No differences were detected in calorie intake, carbohydrate intake, fat intake, protein intake, drinking and alcoholic habit among BMI tertiles. RMR was similar in the different tertiles and the corrected RMR by fat-free mass was higher in first tertile than in the second and third tertiles (44.2 +/- 20.7 vs. 34.5 +/- 9.1 vs. 33.1 +/- 8.5 kcal/kg/day; p < 0.05). In multivariate analysis with a dependent variable (RMR), the fat-free mass remained in the model (F = 7.8; p < 0.05), with an increase of 10.1 (95% CI 3.6-17.5) kcal/day with each 1 kg of fat-free mass adjusted by age and sex. CONCLUSION: Resting energy expenditure in obese patients is not related to the BMI, insulin resistance and dietary intake. RMR is related to fat-free mass in a multivariant model.