Mums and dads with overweight children are often judged, with assumptions made about lazy parenting and fatty diets.
But carrying extra weight in childhood could be down to a mutant gene.
New research at Cambridge and Bristol universities has found that one in 340 of us might be carrying a mutation in a single gene that means we could be up to 37lb heavier – more than two-and-a-half stone – by the age of 18. And that excess weight is likely to be mostly fat.
One of these genes, MC4R, makes a protein produced in the brain and its job is to signal to our appetite centres how much fat we’ve stored.
When the MC4R gene doesn’t work properly, our brains think we have lower fat stores than we do, signalling that we’re starving and need to eat.
These results emerged by studying the MC4R gene in 6,000 people born in Bristol in 1990-91, who were recruited to Children of the 90s, a health study based at the University of Bristol. Whenever a mutation was found, researchers studied what it did in the laboratory and then the impact of MC4R mutations on people’s weight and body fat. The upshot is around 200,000 people in the UK could carry a substantial amount of additional fat because of mutations in MC4R.
The thing is, if you inherit a MC4R mutation you’ll feel the impact of it from birth. The scientists have shown that those children may be on course to be overweight, and even obese. But it will also mean it can be spotted early and precautions taken.
Professor Sir Stephen O’Rahilly, from Cambridge University, one of the study’s authors, said: “Parents of obese children are often blamed for poor parenting and not all children obtain appropriate professional help.
“Our findings show that weight gain in childhood due to a single gene disorder is not uncommon. This encourages a more compassionate and rational approach to overweight children and families, including genetic analysis in all seriously obese children.”
Professor Nic Timpson, Children of the 90s’ principal investigator, and also one of the study’s authors, said: “This work helps recalibrate our understanding of the frequency and functional impact of rare MC4R mutations and will help shape the future management of this important health factor.”
In the longer term, knowledge of the brain pathways controlled by MC4R should help in the design of drugs that help restore people to a healthy weight.