What's the role of genetics in early-onset severe obesity?

Hi there,

Interesting question. In answer to your query, here are a few facts about childhood obesity:

1. Early onset obesity is defined as occurring before the age of 10 - ie you were severely obese in childhood before turning 10.

2. Your BMI has to be 3 standard deviations above the norm.

If there were 100 people that fell within this group, approximately 7 of them would have a genetic mutation in the form of a single point genetic mutation - in other words, 7% of childhood obesity can be directly attributable to your "bad genes".

What about the other 93%? Well, the majority of obesity is still due to a combination of:

1. Too much food intake

2. Lack of physical activity

How do we know that genetics has a role to play in obesity?

We know this as not everyone who grew up in urban or rural environments become obese, which suggests that genetics play a role as well.

Genetics in obesity

Recognized forms of obesity attributable to genes include:

• A deficiency of the leptin and melanocortin-4 receptors
• Mutations in the melanocortin-4 receptor gene
• People with 2 copies of the FTO gene (fat mass and obesity associated gene) have been found to weigh 3–4 kg more and have a 1.67-fold greater risk of obesity compared with those without the risk allele.

Finally, obesity is also a feature in a few rare and inherited syndromes such as:

1. Prader–Willi syndrome
2. Bardet–Biedl syndrome
3. Cohen syndrome, and
4. MOMO syndrome