Obesity is a chronic, complex, and multifactorial disease, characterized by excess body fat. Diverse studies of the human genome have led to the identification of susceptibility genes that contribute to obesity. However, relatively few studies have addressed specifically the association between the level of expression of these genes and obesity. We studied 160 healthy and obese unrelated Mexican children aged 6 to 14 years. We measured the transcriptional expression of 20 genes associated with obesity, in addition to the biochemical parameters, in peripheral white blood cells. The detection of mRNA levels was performed using the OpenArray Real-Time PCR System (Applied Biosystems). Obese children exhibited higher values of fasting glucose (p = 0.034), fasting insulin (p = 0.004), low-density lipoprotein (p = 0.006), triglycerides (p < 0.001), systolic blood pressure and diastolic blood pressure (p < 0.001), and lower values of high-density lipoprotein (p < 0.001) compared to lean children. Analysis of transcriptional expression data showed a difference for ADRB1 (p = 0.0297), ADIPOR1 (p = 0.0317), GHRL (p = 0.0060) and FTO (p = 0.0348) genes. Our results suggest that changes in the expression level of the studied genes are involved in biological processes implicated in the development of childhood obesity. Our study contributes new perspectives for a better understanding of biological processes involved in obesity. The protocol was approved by the National Committee and Ethical Committee Board from the Mexican Social Security Institute (IMSS) (IMSS FIS/IMSS/PRIO/10/011).