Genetics
Childhood obesity is often the result of an interplay between many genetic and environmental factors. Polymorphisms in various genes controlling appetite and metabolism predispose individuals to obesity when sufficient calories are present. Over 200 genes affect weight by determining activity level, food preferences, body type, and metabolism. Having two copies of the allele called FTO increases the likelihood of both obesity and diabetes.As such, obesity is a major feature of a number of rare genetic conditions that often present in childhood:

Prader–Willi syndrome with an incidence between 1 in 12,000 and 1 in 15,000 live births is characterized by hyperphagia and food preoccupations which leads to rapid weight gain in those affected. Bardet–Biedl syndrome
MOMO syndrome
Leptin receptor mutations
Congenital leptin deficiency
Melanocortin receptor mutationsIn children with early-onset severe obesity (defined by an onset before ten years of age and body mass index over three standard deviations above normal), 7% harbor a single locus mutation.One study found that 80% of the offspring of two obese parents were obese in contrast to less than 10% of the offspring of two parents who were of normal weight. The percentage of obesity that can be attributed to genetics varies from 6% to 85% depending on the population examined. Family practices
In the recent decades, family practices have significantly changed, and several of these practices greatly contribute to childhood obesity:
With a decreasing number of mothers who breast-feed, more infants become obese children as they grow up and are reared on infant formula instead.
Colorectal cancer diagnosed in a person with one or more first-degree relative with colorectal cancer or Lynch syndrome associated tumour diagnosed under age 50
5. Person with colorectal cancer and two or more first- or second-degree relatives with colorectal cancer or Lynch syndrome associated cancer diagnosed at any age.It is important to note that these clinical criteria can be difficult to use in practice and clinical criteria used alone misses between 12 and 68 percent of Lynch syndrome cases. Surgery
Prophylactic hysterectomy and salpingo-oophorectomy (removal of the uterus, Fallopian tubes, and ovaries to prevent cancer from developing) can be performed before ovarian or endometrial cancer develops. Treatment
Surgery remains the front-line therapy for HNPCC. Patients with Lynch syndrome who develop colorectal cancer may be treated with either a partial colectomy or total colectomy with ileorectal anastomosis. Due to increased risk of colorectal cancer following partial colectomy and similar quality of life after both surgeries, a total colectomy may be a preferred treatment for HNPCC, especially in younger patients.There is an ongoing controversy over the benefit of 5-fluorouracil-based adjuvant therapies for HNPCC-related colorectal tumours, particularly those in stages I and II. Anti-PD-1 antibody therapy can be effective.Checkpoint blockade with anti-PD-1 therapy is now preferred first line therapy for advanced Microsatellite-Instability–High colorectal cancer. Epidemiology
Though the exact prevalence of Lynch syndrome-causing mutations in the general population remain unknown, recent studies estimate the prevalence to be 1 in 279 individuals, or 0.35%.