Obesity can be diagnosed and classified using the body mass index (BMI), being considered for diagnosis and classification the ranges of 30-34.9 kg/m2 as obesity class I, 35-39.9 kg/m2 as obesity class II and ≥ 40 kg/m2 as obesity class III, also called morbid obesity [1-3].
Obesity presents itself today as an alarming public health problem worldwide, with an overwhelming increase in recent years, being considered an epidemic(2) besides being correlated with the emergence of cardiovascular, cerebrovascular, respiratory, metabolic and oncological diseases [2-7] being its etiology of multifactorial character, being able to be related to nutritional disorders, genetic, psychological, socioeconomic factors and sedentarism . However, one aspect that deserves a lot of attention is changes in the quality of life (QoL) due to weight accumulation, which can negatively influence the most diverse relations of the subject with the world, as well as the form that sees life.
QoL was defined by WHO as the individual's perception of their position in life in the context of the culture and value system in which they live and in relation to their goals, expectations, standards and concerns [9,10]. QoL being a subjective and
multidimensional concept, that is, how the individual perceives himself within certain contexts and in different dimensions. In this context, QoL can be determined through aspects related to physical, social, mental health, general perception of health and functional capacity. For evaluation of QoL without being necessarily correlated with a specific disease generic instruments were developed. Among the instruments used, the WHOQOL-100, a QoL assessment instrument prepared by the WHO Quality of Life Study Group, is composed of 100 items distributed in 6 domains: physical, psychological, level of independence, relationships social, environmental and personal beliefs . Due to its extension, it was noticed the need to create a questionnaire more accessible and faster application. From this questioning, they created their reduced version, the WHOQOL-bref containing 26 questions divided into 4 domains, being: physical, psychological, social relations environment .
Another tool used to evaluate the widely used QoL is the Short-Form 36 (SF-36), which is easy to understand and not as extensive as other existing questionnaires. It consists of a multidimensional questionnaire, divided into 8 domains: functional capacity, physical aspects, pain, general health, vitality, social, emotional and mental health aspects .
Zwaan, et al.  to compare the QOL of obese patients with and without binge eating disorder using two questionnaires, one of which was the SF-36 and another specific Impact of Weight on Quality of Life Questionnaire. The authors verified that both the use of SF 36 and that of the specific questionnaire confirmed the reduction of QoL in this population, especially in the physical domains, but not necessarily confirmed for the domains related to mental health.
In the study by Larsson, et al.  the QoL of 30 obese class III patients in the 16- and 64-year age groups of both sexes was evaluated using the SF-36 as a tool. The authors concluded that there was impairment in QoL in both physical and mental aspects compared to the control group. These results differ from those observed in our study, where there were no differences in QoL of obese class III compared to non-obese for mental health and emotional aspects. Comparando o SF-36 com o Assessment of Quality of Life (AQoL)-8D para sua validacao, Khan, et al.  evaluated 196 obese, 61% class III, 28% class II and 11% class I, predominantly female sex. Of the 16 dimensions assessed in the questionnaires, this study reached a total of 14 dimensions with significantly lower values, suggesting the association between obesity and its effects on physical, social and psychological issues.
In the study by Sulivan, et al.  BMI between 34 and 38 kg / m2) compared to a group of eutrophic individuals, it was observed that obese individuals presented an important decrease in health status, with a higher impact for the components of the sample women.
Doll, et al.  also investigated the interaction between obesity and QoL. The authors observed that physical as well as emotional well-being deteriorated in a manner directly proportional to weight gain. The same results were found by Kolotkin et al (2001), who compared the QoL of 996 obese patients with that of non-obese individuals, stating that bio psychosocial aspects were markedly reduced as a function of obesity.
In conclusion, obese individuals, especially the morbidly obese, presented worse quality of life when compared to nonobese individuals in the most diverse domains even with different evaluation tools.