Exercise Training and Fitness in Severe Obesity
Condition: Obesity
MeSH terms: Obesity
Study type: Interventional

Summary: 
      Obesity is commonly associated with insulin resistance and hyperinsulinemia, which seem to be
      linked with an impaired ability to oxidize lipids, particularly in class III obese
      individuals [Body Mass Index (BMI): > 40 kg*m-2]. Exercise training is an effective strategy
      to improve insulin sensitivity and to reduce the risk of type 2 diabetes.

      This study aimed to compare the effects of two different 2-wk-long training modalities
      [continuous at the intensity eliciting the maximal fat oxidation (Fatmax) versus adapted high
      intensity interval training (HIIT)] on aerobic and metabolic fitness of class II and III
      obese men. It was hypothesized that, because of the nature of HIIT in the stimulation of
      rapid changes, aerobic fitness, fat oxidation rates during exercise and insulin sensitivity
      would be improved to a greater extent when adapted HIIT compared to Fatmax training.
    

Detailed description: 
      Obesity is commonly associated with insulin resistance and hyperinsulinemia, which seem to be
      linked with an impaired ability to oxidize lipids, particularly in class III obese
      individuals [Body Mass Index (BMI): > 40 kg*m-2] (1). Exercise training is an effective
      strategy to improve insulin sensitivity and to reduce the risk of type 2 diabetes (2). It has
      been suggested that 8 (3) or 10 wk (4) of an individualized moderate exercise training
      program at intensity (Fatmax) that elicits maximal fat oxidation (MFO) may significantly
      increase the fat oxidation rates (FORs) during exercise; it may also increase the muscle
      oxidative capacity in overweight and class I obese men. The effects of an individualized
      Fatmax training program of a shorter duration have never been investigated.

      High-intensity interval training (Wingate-based HIIT) has been shown to induce similar
      adaptations as traditional training at a moderate intensity following 6 wk of training in
      healthy adults despite the lower training volume (5). This suggests that HIIT may be a
      time-efficient alternative (6). Recently, HIIT was also reported to rapidly induce
      adaptations that are linked to improved health-related outcomes in sedentary and
      overweight/obese individuals (7, 8).

      This study aimed to compare the effects of two different 2-wk-long training modalities
      [continuous at the intensity eliciting the maximal fat oxidation (Fatmax) versus adapted high
      intensity interval training (HIIT)] on aerobic and metabolic fitness of class II and III
      obese men. It was hypothesized that, because of the nature of HIIT in the stimulation of
      rapid changes, aerobic fitness, fat oxidation rates during exercise and insulin sensitivity
      would be improved to a greater extent when trained with adapted HIIT compared to Fatmax
      training.

      A group of twenty obese men (BMI≥35 kg*m-2) will be assigned to Fatmax group or to adapted
      HIIT group. Both groups will perform 8 cycling-sessions matched for mechanical work spread
      over 14 days [40-50 min continuous exercise at ~60-70% of the maximal heart rate (Fatmax) or
      10x60-s cycling intervals a ~90% maximal heart rate interspersed with 60-s recovery (HIIT)].
      Aerobic fitness and fat oxidation rates (FORs) during exercise will be assessed prior to and
      following the training with a maximal incremental test. Blood samples will also be drawn to
      determine hormones and plasma metabolites levels. Insulin sensitivity was assessed by the
      homeostasis model assessment of insulin resistance (HOMA).

      The experimental design will consist of the following: 1) maximal ramp incremental test, to
      determine peak power output of each subject. 2) pre training test with blood samples, maximal
      incremental test (Incr) to determine the whole-body fat oxidation kinetics and Fatmax in the
      first phase (IncrP1) and the maximal parameters in the second phase (IncrP2) of the test. 3)
      2-wk training intervention, Fatmax or HIIT and 4) post-training test, control maximal
      incremental test with blood samples.

      A 3-way repeated-measures ANOVA (time x group x exercise intensity) will be performed to
      compare the investigated variables.
    

Intervention name(s): Fatmax group; HIIT group
Intervention type(s): Other; Other
Intervention description(s): For the Fatmax group each session will consist of 40-50 min of continuous exercise with an intensity that corresponded to the individual Fatmax (moderate intensity); For HIIT group, each session will consist of 10x60-s cycling intervals interspersed with 60-s of recovery. The workloads will be selected to elicit a heart rate of ~90% maximal heart rate during the intervals with a pedal rate of 90-100 revolutions.min-1, whereas during recovery, the participants will be allowed to pedal against a resistance of 50 W
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: exercise; fat oxidation; indirect calorimetry; insulin sensitivity; weight management