Acerca do impacto do aumento de massa corporal sobre a pele humana - contribuicao para o estudo dos efeitos da obesidade sobre a normal fisiologia cutanea

Resumen

Defined as an epidemic by the WHO, obesity affects, according to recent studies, more than a third of adults in the United States. In Portugal, the scenario is identical, and recent studies show that about two thirds of the population is overweight or obese. As the prevalence of this disease continues to rise alarmingly, studies on the impact of obesity in terms of human physiology multiply. Being human obesity a factor in the pathophysiology of several co-morbidities, it is justified to look for a pattern characterization, morphological and functional, of an organ that undergoes major changes with this disease, with obvious impact on health and quality of life of these patients - the skin. For this reason, the following question was asked: " Which are the main functional differences affecting in vivo human skin due to excessive weight, particularly considering the skin water dynamics and its biomechanical behavior ?" To verify this hypothesis we aimed the following objectives: (I) to develop a methodology that enables to identify key biometric variables, anatomical regions and other determinants of the functional definition of the skin for obese patients compared with normal skin physiology; (II) to determine the existence of changes in skin hydration and biomechanical behavior related to the weight excess. For the first objective, a study in 28 volunteers, female, aged between 19 and 46 years (23 ± 5 years), healthy and with normal BMI according to the WHO criteria (between 19 9 and 24.9 kg/m2) was performed. For the second objective, we selected a convenience sample of 89 volunteers, female, aged between 19 and 46 years ( 32 ± 7 years old), healthy. The sample was divided into four groups - Group I, BMI between 19.9 and 24.9 kg/m2, Group II with BMI between 25 and 29.9 kg/m2, Group III, with BMI between 30 and 39.9 kg/m2 and group IV, with a BMI above 40 kg/m2. Measurements of skin hydration and biomechanical parameters were made in the face (zygomatic and forehead areas), the breast region and the abdominal region. Regarding the first objective, a methodology able to identify the biometric changes resulting from changes of skin envelope and barrier function was developed. Regarding the second objective, alterations in all variables with weight change were identified, as well as significant correlations between hydration and biomechanical variables for all studied anatomical areas. Results obtained for each goal, suggests the following conclusions: (I) this developed methodology proved to be especially useful for the study of these cutaneous features in obese patients, being reproducible in all the different groups of volunteers, with different body mass index (BMI), allowing to identify major changes in hydration and biomechanical behavior, apparently related to the weight excess; (ii) the significant correlation between hydration and biomechanical variables contributes to strengthen the interdependence, although not yet sufficiently substantiated between these variables. It was also possible to identify a global indicator able to reflect the studied skin changes, potentially useful for a quick assessment of the functional state of the skin due to the overweight. Results also suggest that a drastic weight reduction (exceeding 20%) as this registered in obese (morbidly obese) after weight reduction surgery, allows to recover biomechanical and hydration indicators to values comparable to those obtained in normal BMI patients. These conclusions do allow us to present our hypothesis as a Thesis and affirm that: - The weight excess determines the change of some functional cutaneous keyvariables, affecting both the skin water physiology and the barrier function and its biomechanical behavior as well, and these might be associated to all related pathophysiology processes. These changes do not occur linearly as a function of the weight gain which, in any case, contributes to illustrate the complex relationship between these three different tissues (epidermis, dermis and hypodermis) included in the general designation of "skin physiology".