Obesity: considerations about etiology, metabolism, and the use of experimental models

Abstract

Studies have been conducted in order to identify the main factors that contribute to the development of obesity. The role of genetics has also been extensively studied. However, the substantial augmentation of obesity prevalence in the last 20 years cannot be justified only by genetic alterations that, theoretically, would have occurred in such a short time. Thus, the difference in obesity prevalence in various population groups is also related to environmental factors, especially diet and the reduction of physical activity. These aspects, interacting or not with genetic factors, could explain the excess of body fat in large proportions worldwide. This article will focus on positive energy balance, high-fat diet, alteration in appetite control hormones, insulin resistance, amino acids metabolism, and the limitation of the experimental models to address this complex issue.

The differential effects of high-fat and high fructose diets on the liver of male albino rat and the proposed underlying mechanisms

“…In addition, the nutrition above the packing capability of adipose tissue results in precipitation of TG in different organs, causing steatosis and even organ dysfunction [38]. Moreover, high consumption of carbohydrates with or without fats increases the risk of obesity and diabetes [25]. Non-alcoholic fatty liver disease (NAFLD) is the commonest sort of liver diseases in the Western countries [21].…”

Early Overfeed-Induced Obesity Leads to Brown Adipose Tissue Hypoactivity in Rats

“…Obesity is characterized by fat accumulation resulting from energy imbalance, expressed as a higher intake and lower expenditure of calories [4]. The excess calories are stored as lipids in white adipose tissue (WAT), which is the major form of energy storage.…”

Efeitos do exercício físico na resistência à insulina em indivíduos obesos

“…A obesidade é um distúrbio metabólico que se caracteriza por um estado inflamatório crônico e acúmulo excessivo de gordura corporal, constituindo-se em um risco para a saúde e para o desenvolvimento de outras patologias, como Diabetes Melittus tipo 2, hipercolesterolemia, hipertensão arterial, doenças cardiovasculares, síndrome de apneia obstrutiva do sono, comprometimentos osteomioarticulares e diversos tipos de cânceres. 11,12 A obesidade está fortemente associada com aumentos nos níveis circulantes do fator de necrose tumoral-alfa (TNF-α), enquanto a perda de peso e atividade física reduz os níveis sistêmicos desta citocina; já, níveis elevados de TNF-α induzem à resistência à insulina, hipertrigliceridemia, baixos níveis de HDL e altos níveis de LDL na circulação; estando também associada com a hipertensão arterial, pela ativação do sistema renina-angiotensina e forte correlação com a síndrome metabólica. 13 A obesidade central pode favorecer um aumento da liberação de ácidos graxos livres, frutos da lipólise, devido à sua elevada sensibilidade, através da ação das catecolaminas (epinefrina, norepinefrina e dopamina), as quais inibem substancialmente a captura da glicose, podendo ocasionar hiperglicemia e posteriormente hiperinsulinemia.…”