Obesity is a medical condition defined asan accumulation of excess of body fat that lead to many health problems andreduced life expectancy. Obesity usually associates with hypertension,diabetes, cardio vascular diseases (CVDs) and dyslipidemia (Grundy, 2004).
Obesity is commonly measured by theBody mass index (BMI), which is calculated as the weight in kilograms dividedby the square of the height in meters. Normal BMI is considered between18.5 to 24.9. However, Overweight, obesity and extreme obesity are classifiedas the following: the BMI for overweight is 25.0 or greater and less than 30.
0,obesity BMI is 30.0 or greater and lastly extreme obesity is BMI 40.0 orgreater (Mendy, Vargas, Cannon-Smith, & Payton, 2017). The prevalence and incidence of obesityare increasing rapidly to epidemic proportions in industrial areas as well asworldwide. It has increased three folds between 1975 and 2016 and more than 1.9billion adults were overweight in 2016 (WHO, 2017).
Obesity results from energy imbalancebetween energy intake and energy usage at which both environmental and geneticfactors play a role in its onset. Environmental risk factors include physicalinactivity, consumption of fast foods, sugary food and inadequate sleep. Inaddition, genetic factors contribute to the onset of obesity.
Obesity could bedue to monogenic; mutation in a single gene, or polygenic; mutations in morethan one gene. Although those genes do not directly cause obesity, theycontribute to its onset and development in parallel with other geneticalterations (O’Rahilly, Farooqi, Yeo, & Challis, 2003).Many studies that have provided dataabout obesity risk factors were focused on western countries more than anyother areas. The western studies’ conclusions do not necessarily apply to otherpopulation due to variety of genetic and environmental factors. Recent progressvia genome-wide association studies (GWAS) has identified many additionalgenetic factors that appear to inflate the risk of disorders in someindividuals (Zeggini et al., 2008). Studying differentpopulations with different background such as Qatari population which has asmall population size and high consanguinity will clearly provide betterunderstanding of obesity risk factors world widely.
Consanguinity has reached54% in Qatar, and obesity prevalence is more than 70%. The high incidence and prevalenceof obesity has been due to lifestyle changes after discovering oil in gulf areaand increased wealth (Tomei et al., 2015). Development andbuilding of cities has occurred rapidly which has changed the old lifestyle oftraveling, to sedentary lifestyle, which contributed to increased obesity.Recent GWAS studies have showed relationship between genes and obesity, but itis not well known if those genetic markers influence similar risks in people ofdifferent descent (Larson et al., 2007). Distribution ofdiseases related to alleles between different population is uneven speciallyfor recessive disorder such as monogenic obesity of mutation in Leptin Receptor(Hindorff et al., 2009).
The risk of a genetic marker identified by GWASmight vary according to the population being studied cause populations withdifferent ancestry have variability of allelic frequency (Meyre et al., 2009).