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

Abstract

Objective 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. Methods Fifty-two obese female adults (age = 43.6±10.9 years; BMI = 38.5±5.2 kg/m 2 ) 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 (VO 2peak ), 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, %HR max , VO 2 and %VO 2peak 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. Results For each HR, %HR max , VO 2 and %VO 2peak variable there was a positive significant correlation (P<0.01) between IVT and MFO. No significant differences were found for HR, %HR max , and VO 2 between IVT and MFO. %VO 2peak was significantly higher at IVT than at MFO (P = 0.03). MFO rates were significantly higher in OBIII women than in women of the other two classes. In all subjects, IVT was within the fat max zone. Conclusion The use of HR and VO 2 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.

Exercise Fat Oxidation Is Positively Associated with Body Fatness in Men with Obesity: Defying the Metabolic Flexibility Paradigm

“…In contradiction with this paradigm, we observed a positive association between body fatness and the fat oxidation increase in response to physical exercise at FATmax ( Table 2 ). The results of the present study agree with Emerenziani et al, [ 25 ] who observed a higher MFO in women with class III obesity compared with class I and II individuals, and supports previous studies reporting a higher MFO [ 26 ] and TFO [ 27 , 28 ] in subjects with obesity when compared against lean counterparts, as well as a lower RER peak during moderate-intensity exercise [ 27 ]. Rationale for a positive association between body fatness and exercise fat oxidation are: (I) increased free fatty acid circulating levels and (II) augmented intramuscular triglyceride oxidation [ 6 , 27 , 28 ].…”

Changes in substrate utilization rates during 40 min of walking within the Fatmax range

“…As the participants were sedentary and overweight with a low aerobic capacity (19,42), the discontinuation of lipid oxidation with constant low-intensity exercise may be attributed to their metabolic inflexibility. In this context, as an alternative method, the use of the individual ventilatory threshold can be a useful parameter that identifies physical activity that maximizes fat oxidation in obese individuals (14).…”

Walking for subjects with type 2 diabetes: A systematic review and joint AMD/SID/SISMES evidence-based practical guideline

“…For most individuals with type 2 diabetes engaging in a walking-based exercise training, the sustainable intensity between 40 and 59% heart rate reserve (HRR, calculated as a percentage of maximum heart rate minus resting heart rate), corresponding to a rating of perceived exertion (RPE) of 11e13 on a 6e20 scale [89] (Table 3) should be encouraged, even if lower intensities should be initially prescribed for very deconditioned patients. Unfortunately, exercise intensity is rarely prescribed on an individual basis, although some studies have recently argued for the use of tailored approaches, with particular emphasis on the individual ventilatory threshold [90,91], in order to improve cardiorespiratory fitness and promote weight loss and maintenance. Further studies are still required to confirm that the individual ventilatory threshold may be an appropriate guide in prescribing exercise intensity in these patients.…”