The study was suspended due to the inability to complete the sample after more than a year of attempts. Various adherence strategies were tested, but adherence to the interventions remained too low.

It is estimated that by 2030 one in five women and one in seven men will be obese, equivalent to more than 1 billion people around the world. It should be noted that the largest number of people with obesity live in countries with low and moderate-income. In 2019, more than 160 million years of healthy life were lost in the world, due to a high body mass index (BMI), this represents more than 20% of all years of healthy life lost due to chronic diseases. Therefore, it is essential to stop the increase in obesity and reduce it at all ages, which demands comprehensive actions at the global level. Scientific evidence suggests that people with a normal BMI, but with abdominal obesity, have a higher mortality risk compared to those with a similar or even higher BMI. In addition, visceral adiposity has been associated with worse survival and with colorectal cancer.

Several methods of physical exercise have been used to counteract the adverse effects of obesity, including high-intensity functional circuit training (HIFCT). Scientific evidence indicates that HIFCT reduces fat mass, body mass, BMI, and waist circumference and improves muscle strength, maximal oxygen uptake, and health-related quality of life in overweight, obese, inactive, and with other diseases. However, no research assessed intra-abdominal fat (IAF), which, more than subcutaneous fat, is associated with cardiovascular risk factors. In addition, these studies had important methodological limitations. Therefore, the primary purpose of this study is to identify the effect of two HIFCT protocols, prolonged load (HIFCT-P) and short load (HIFCT-S), performed in a virtual environment for ten weeks on intra-abdominal fat in people between 18-40 years-old with abdominal obesity.

A randomized controlled trial with parallel arms (HIFCT-P and HIFCT-C) based on a non-inferiority hypothesis comparing two proportions. Each participant will carry out 30 sessions, three times a week, in a virtual environment. General, concentrated, and block circuits will be used, with the same exercises, but with different load distribution and different order between them. Both HIFCT-P and HIFCT-S will carry out six initial adaptation sessions through a general circuit composed of 12 exercises. Different muscle groups will be alternated. The exercises will be performed at speeds between 35 and 55 beats per minute (bpm), to ensure intensities between 50% - 60% in sessions 1 to 3, and between 70% - 80% in sessions 4 to 6. The Modified Borg Rating of Perceived Exertion Scale (RPE) will be used to control intensities. From session seven to session 30, HIFCT-P and HIFCT-S will perform the same exercises but with a different load distribution.

Inclusion Criteria:

• Healthy women and men.
• Physical activity (<600 to ≤1500 MET/min/wk).
• Waist circumference (≥87cm).

Exclusion Criteria:

• Have performed high intensity exercises or HIFCT in the last two months.
• Smoking.
• History of cardiovascular disease.
• History of coronary heart disease.
• Pregnancy.
• Breast-feeding women.
• Psychological, neuromotor, and/or osteo-muscular conditions that may affect participation in an exercise program.