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Here in this paper, we describe the relationship between type 2 diabetes and obesity including different types of obesity and its genetic predisposition. Several physiological conditions that are capable of changing the level of expression of numerous genes involved in metabolic pathways, energy production, and regulating body weight, are created due to the expansion of our modern society and abundance of caloric foods. It appears that a variety of genes could participate in adaptation of human body to its revolutionary limitations. 

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In 2007, based on genome-wide association studies, FTO gene was discovered. An association of single nucleotide polymorphisms (SNPs) in the fat mass and obesity-associated (FTO) gene region with body mass index (BMI) was identified in multiple populations, and indeed it leads to finding FTO gene as the first locus related to obesity.  In this review, we explore the genetic epidemiology of FTO and discuss how its complex biology might link to the regulation of body weight.
In the present mini review study, In vivo and In vitro researches of complex biological FTO, have been proposed. Also, association of FTO gene with obesity and obesity-related diseases has been investigated.
The effect of FTO SNPs on obesity traits in African and Asian populations is similar or somewhat smaller than in European populations.  FTO SNPs do not influence physical activity levels. Growing evidence from studies suggests that FTO along with subtle changes in food intake confer an increased risk of obesity. Defect in  FTO gene creates clear phenotypes in postnatal growth retardation and the developmental problems.
 

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Aim and Background:
Today many genes have been reported that affect obesity in complex ways. One of these genes is the polymorphism of ACE gene. Angiotensin converting enzyme (ACE) is an important factor that can affect adipose tissue metabolism. The aim of this study was to investigate the relationship between ACE gene polymorphism and obesity in the population of Ardabil province.
Methods and materials:
The 172 people attending this study were divided into two individuals of BMI < 30 and BMI≥ 30 according to their body mass index.  The DNAs of the sample were extracted using the saturated salt method and the extracted strains from normal and obsess participants were compared with each other under electrophoresis by PCR.
Results:
In the group by BMI<30 there were 57.5% male and 42.5% female participants. By contrast, in the group by BMI≥30, there were 42% male and 58% female participants. The average age of the participants in BMI<30 group was 47.55 years but in the BMI≥30 group it was 52.45 years. BMI mean of the people in BMI<30 was 25.19 and BMI mean of the people in BMI≥30 was 32.58. DD genotype frequency in BMI≥30 was 0.83 which is more than the frequency of BMI<30 (0.83 against 0.71).
Conclusion:
The obtained results of this research suggested that genotype DD in ACE gene has a relationship with the obesity of Ardabil province population.
 

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Aim and Background
The process of obesity is complex and many factors, including two key hormones, leptin and insulin are involved. The homeostatic role of insulin in energy stability is reduced by insulin resistance. It is possible that leptin and insulin have a regulatory role on each other, therefore, the present study investigated the relationship between BMI, leptin , insulin and insulin resistance.
Materials and methods
In this cross-sectional study, 140 women were examined in 2 equal groups with normal (18.5-24.9) or obese (≥ 30) BMI. After fasting for 10-12 hours, 10 cc of venous blood was taken from the subjects, Blood sugar was measured by glucose oxidase, insulin and leptin by ELISA method, and HOMA-IR index was calculated. The data were expressed as mean ± standard deviation. P < 0.05 was considered statistically significant.
Results: There was a significant difference between the groups in terms of leptin level, and there was a significant correlation between BMI and plasma leptin level of the studied subjects, r=0.07 and P<0.01. Also, there was a significant relationship between serum leptin and fasting insulin (r = 0.05 and P < 0.01. In terms of the HOMA-IR, a significant difference between the groups was observed which was higher in obese than in normal.
Conclusion
BMI is the main factor in regulating leptin levels. Probably the continuity of insulin and leptin levels is due to the determining role of BMI on both of them.