Genetic Obesity Clears Parents of Blame?

As obesity is widely believed to be a condition resulting from people’s poor lifestyle choices, it is only normal to also believe that childhood obesity is simply the result of poor parenting skills. Thus, in severe cases, childhood obesity has been likened to childhood abuse and there are cases where obese children have been brought to the attention of social services and child protection agencies.

As now reported by the BBC, at least a few such parents have recently been exonerated after the discovery that the severe obesity that resulted in their children being formally placed on the social services ‘at risk’ register on the assumption that the parents were deliberately overfeeding the kids, were removed from the register after the discovery of a new genetic defect that largely explained the kids’ excess weight.

This new genetic defect, consisting of large chromosomal deletions associated with severe early-onset obesity, was reported by Elena Bochukova and colleagues from the University of Cambridge, UK, in an early online publication in NATURE.

In their study of 300 Caucasian patients with severe early-onset obesity, 143 of whom also had developmental delay, the researchers identified several rare copy number variants that were recurrent in patients but absent or at much lower prevalence in controls.

Five patients had overlapping deletions on chromosome 16. Two patients harboured a larger de novo chromosome 16 deletion, extending through a 593-kilobase region previously associated with autism and mental retardation. In an independent sample of 1,062 patients with severe obesity, the smaller chromosome 16 deletion was found in an additional two patients. All deletions include SH2B1, which is involved in leptin and insulin signaling.

All deletion carriers exhibited hyperphagia and severe insulin resistance disproportionate for the degree of obesity.

Not only does this study point to an important role of this region of chromosome 16 (and possibly SH2B1) for rare cases of early-onset hyperphagic obesity, but it also shows that even genetic obesity is a remarkably heterogeneous disorder.

This study certainly serves as a reminder that jumping to conclusions about peoples lifestyle “choices” based simply on their appearance is never a good idea.

Edmonton, Alberta