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Obesity research is advancing swiftly, but the increase in obesity prevalence is faster. Over the past three decades, researchers have found that biopsychosocial factors determine weight gain much more than personal choices and responsibility. Various genes have found to predispose people to obesity by interacting with our obesogenic environment. In this review, we discuss the impact of physical inactivity, excessive caloric intake, intrauterine environment, postnatal influences, insufficient sleep, drugs, medical conditions, socioeconomic status, ethnicity, psychosocial stress, endocrin disrupting chemicals and the gastrointestinal microbiome.on the occurrence of obesity.
KEYWORDS: obesity, genetics, environment, modifiable, causes, genetics, epigenetics, modifiable factors
Introduction
The World Obesity Federation estimates that 800 million people are currently living with obesity, of whom 39 million are children under 5 years (2020) and 340 million are children and adolescents between the ages of 5 and 19 years. Moreover, there are at least 1 billion more people at risk of becoming overweight or obese.
The impact of obesity on individuals and society is evident by considering the chronic diseases resulting from obesity (type 2 diabetes mellitus (T2D), hypertension, dyslipidaemia, osteoarthritis, sleep apnoea and various cancers) and the associated disabilities, which can lead to decreased productivity.
Although efforts to treat obesity are underwaywith increasing success, we have failed to control the relentless increase in obesity. Determining the exact causes of obesity and understanding their pathophysiology is a major stumbling block. This was fully addressed in the landmark foresight report first published in 2007, which identified the complex drivers of obesity and outlined a plan to prevent and treat it.1 This report envisions the obesity occurrence and goals up to 2050 and suggests appropriate measures to achieve a sustainable decrease in the prevalence of obesity.1
The causes of obesity are multipronged and inter-related. To simplify we describe them here as non-modifiable and modifiable factors.
Non-modifiable factors
Genetic
There have been several studies over the past 20 years on genetic obesity, which have found that genetic mutations (abnormal changes in DNA sequence), polymorphisms (normal variation in a DNA sequence, which is common in the population) and changes in gene expression (the process by which information encoded in a gene is turned into a function), all have a role in predisposing ndividuals to obesity.
Initially, candidate gene studies (ie...