High Intensity Interval Circuit Training on Resting Metabolic Rate in Overweight Adults
Condition: Overweight and Obesity
MeSH terms: Overweight
Study type: Interventional

Summary: 
      This is the first study to examine changes in resting metabolic rate up to 72 hours following
      an exercise session, and how these changes may be affected by 12 weeks of high intensity
      interval circuit training (HIICT). Various training programs that have been implemented in
      previous studies have investigated changes in resting metabolic rate only for the first 2-8
      hours following an exercise session.

      Briefly, the results of this study will provide insight into the following:

        1. To what extent and for how long does HIICT increases the resting metabolic rate
           following an exercise session?

        2. How can this exercise program enhance metabolism without any dietary or other exercise
           intervention?

        3. What is the caloric deficit that will result from 3 months of HIICT and how to what
           extent this deficit will influence body weight reduction?
    

Detailed description: 
      According to the World Health Organization, overweight and obesity are defined as as abnormal
      or excessive fat accumulation, that presents a risk to health. Body Mass Index (BMI) is a
      useful population-level measure of overweight and obesity in adults, defined as follows: BMI
      = [weight (kg)] / [height (m)^2]. Individuals with BMI>25 kg/m^2 are considered overweight,
      whereas individuals with BMI>30 are considered obese. The higher the BMI, the greater the
      risk of developing non-communicable diseases, such as cardiovascular disease, diabetes
      mellitus and various forms of cancer. Obesity is now the most widespread disease in the
      developed world. It has been estimated that over 1.9 billion adults (39% of the population)
      are overweight, of whom 600 million (13% of the population) are obese. These rates are
      translated into a significant economic impact on a county's health care system; therefore,
      drastic measures are needed. The major cause of obesity is an energy imbalance between
      caloric intake and energy expenditure in favor of the former. Thus, changes in lifestyle that
      affect the energy balance, such as participation in an exercise program, can reduce body
      weight and, therefore, contribute to obesity treatment.

      The recommendation of physical activity for significant weight loss involves prolonged
      exercise of moderate to high intensity that gradually increases to ~250 minutes/week.
      Resistance training is also recommended as it activates the neuromuscular system and can
      improve functional ability. On the other hand, High Intensity Interval Training (HIIT), which
      mainly involves a cardiovascular exercise strategy alternating short periods of intense
      anaerobic exercise with less intense recovery periods, are proposed because they are
      time-efficient. In addition, HIIT improves aerobic capacity and body composition, which is
      related to resting metabolic rate and mitochondrial metabolism of skeletal muscle in both
      healthy and overweight and obese adults. Changes caused by HIIT in mitochondrial function may
      explain the greater efficacy in inducing positive metabolic adaptations compared to
      traditional endurance or resistance protocols, even when not accompanied by dietary weight
      loss strategies.

      Resting metabolic rate is defined as the energy expenditure required to maintain the normal
      physiological processes of the body at rest and accounts for 60-75% of the total daily energy
      expenditure. Small increases in resting metabolic rate could long-term positive effects on
      weight management. Energy expenditure is increased not only during exercise, but also for
      some hours post-exercise. To date, it has been observed that this increase in resting
      metabolic rate can last for up to 48 hours following an exercise session, especially
      following resistance training. More specifically, in a study where 7 women (22-35 years old)
      participated in a resistance training program (100 minutes/session, 10 exercises of 5 sets
      with 10-15 repetitions per set), there was an increase in their resting metabolic rate by 13%
      at the first 3 hours and an increase by 4.2% at 16 hours following an exercise session. On
      the other hand, a 10-week (3 session/week) strength training program with an intensity of
      65-85% of the maximum heart rate based on age (gradual increase in intensity), did not appear
      to cause any changes in resting metabolic rate following an exercise session. However, in
      another study where resistance training (strength protocol of 3 sets with 10-15 repetitions
      per set at the beginning of intervention up to 4-8 repetitions at the end of the
      intervention) was combined with endurance training (65% to 85% with an intensity of 65-85% of
      the maximum heart rate based on age, of increasing intensity), it was observed that resting
      metabolic rate increased following an exercise session.

      It is important to note that, according to the available literature, it has been shown that
      training studies have been examined changes in resting metabolic rate only up to 2-8 hours
      following an exercise session. Therefore, the aim of the present study is to investigate the
      effect of a 12-week HIICT protocol with portable equipment on changes in resting metabolic
      rate 24, 48 and 72 hours following an exercise session.

      Flow of the research design:

        1. Baseline: Anthropometric and physiological measurements (including a Resting Metabolic
           Rate (RMR) measurement following an overnight fast).

        2. One-week familiarization period: Volunteers will participate in two exercise sessions in
           order to learn the right techniques. RMR will be measured 24, 48 and 72 hours following
           the last exercise session. Moreover, participants will be given instructions and then
           they will record their diet for 3 days (2 week days and one weekend day).

        3. Initiation of the 12-week HIICT program: The program will be supervised and portable
           training equipment will be used. There will be 3 exercise sessions per week
           (Monday-Wednesday-Friday). The program will be divided into 3 phases (4 weeks each
           phase), where exercise intensity will increase gradually.

        4. 1st phase: RMR will be measured 24 hours before, as well as 24, 48 and 72 hours
           following the last exercise session of the phase (e.g. at the end of the 4th week of the
           program). Anthropometric and physiological measurements will also be conducted.
           Moreover, participants will record their diet for 3 days (2 week days and one weekend
           day).

        5. 2nd phase: Exercise intensity will increase. The same measurements with phase 1 will be
           conducted.

        6. 3rd phase: Exercise intensity will increase. The same measurements with phases 1 and 2
           will be conducted.
    

Intervention name(s): Exercise training - Phase 1; Exercise training - Phase 2; Exercise training - Phase 3
Intervention type(s): Other; Other; Other
Intervention description(s): Phase 1 is the first 4 weeks of the 12-week training program.; Phase 2 is the next 4 weeks following phase 1 of the 12-week training program. The exercise intensity during exercise bouts in this phase is increased compared to the exercise intensity applied in phase 1.; Phase 3 is the last 4 weeks of the 12-week training program. The exercise intensity during exercise bouts in this phase is increased compared to the exercise intensity applied in the previous phases.
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: The 12-week training program will be divided into 3 phases (4 weeks each phase). Completion of each phase means that the subjects have increased their physical fitness and will get to the next phase where the intensity of exercise will increase in order to gain more physical fitness benefits (e.g. increased caloric expenditure). There will be a control group as well, where participants will not participate in any intervention.
Masking: None (Open Label)
Primary purpose: Treatment