Research Article: Relationship between individual ventilatory threshold and maximal fat oxidation (MFO) over different obesity classes in women

Date Published: April 11, 2019

Publisher: Public Library of Science

Author(s): Gian Pietro Emerenziani, Dafne Ferrari, Chiara Marocco, Emanuela A. Greco, Silvia Migliaccio, Andrea Lenzi, Carlo Baldari, Laura Guidetti, Laurent Mourot.


The use of the Individual Ventilatory Threshold (IVT), as parameter to prescribe exercise intensity in individuals with obesity, has become more frequent during the last years. This study aimed to evaluate the relationship between IVT and Maximal Fat Oxidation (MFO) in women with obesity.

Fifty-two obese female adults (age = 43.6±10.9 years; BMI = 38.5±5.2 kg/m2) were included in this study. According to the BMI classification, subjects were divided into three groups: Obese Class I (OBI, n = 16); Obese Class II (OBII, n = 20) and Obese Class III (OBIII, n = 16). All subjects performed an incremental graded exercise test to evaluate peak oxygen uptake (VO2peak), IVT and MFO. MFO was evaluated using a stoichiometric equation. Fat max zone was determined for each subject within 10% of fat oxidation rates at MFO. For each HR, %HRmax, VO2 and %VO2peak variable, Pearson’s correlation test was done between IVT and MFO exercise intensity. When statistical correlation was found we used a comparative statistical analysis to assess differences between IVT and MFO. Statistical significance was set at P ≤ 0.05.

For each HR, %HRmax, VO2 and %VO2peak variable there was a positive significant correlation (P<0.01) between IVT and MFO. No significant differences were found for HR, %HRmax, and VO2 between IVT and MFO. %VO2peak was significantly higher at IVT than at MFO (P = 0.03). The use of HR and VO2 corresponding to IVT could be a useful parameter not only to improve cardiorespiratory fitness but also to prescribe physical activity that maximize fat oxidation in obese subjects.

Partial Text

Obesity is a condition characterized by an increased fat accumulation that impairs health and, according to the World Health Organization (WHO) over 650 million of subjects were obese in 2016 [1]. One of the best approaches to contrast the development of obesity is an healthy lifestyle which should combine physical activity (PA) with a balanced diet. According to the WHO classification, there are three different classes of obesity based on BMI values: obesity Class I (OBI) when BMI is between 30–34.9 kg/m2, Obese Class II (OBII) when BMI is between 35–39.9 kg/m2 and Obese Class III (OBIII) when BMI is ≥ 40 kg/m2.

Subjects’ anthropometric and physiological characteristics are depicted in Table 1. Regarding the anthropometric characteristics, significant difference for weight was found (OBI vs OBII (P<0.001); OBI vs and OBIII (P<0.001); OBII vs OBIII (P<0.05) among groups (Table 1). No statistical differences were found between pre-menopause and menopause condition for HR (P = 0.06), %HR (P = 0.72), VO2 (P = 0.88), %VO2 (P = 0.35) at IVT and for HR (P = 0.10), %HR (P = 0.67), VO2 (P = 0.92), %VO2 (P = 0.22) at MFO. The main objective of this study was to determine the relationship between IVT and MFO in women with class I, II and III obesity. It has been known that the use of IVT as a parameter to individualize exercise intensity might be helpful to improve body composition and physical fitness in obese adults [4, 6]. Moreover, the intensities at which the MFO occurs (Fatmax) has been used for the prescription of PA, especially in weight loss programs, to decrease body mass, BMI and, percentage of body fat [13, 28]. However, different obesity conditions may influence not only physical performance but also substrate utilization during moderate exercise intensity. The results presented in this manuscript demonstrate that the use of HR and VO2 corresponding to IVT could be a useful parameter to prescribe PA with the aim of improving cardio-respiratory efficiency and maximizing fat oxidation in obese subjects. Moreover, our results showed that MFO was higher in OBII than the other two obesity classes, and this difference might be justified by higher VO2 expressed as ml/min in OBIII group than OBI and OBII groups.   Source:


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