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

Doctor's Answers (2)

Hi there,

Thanks for your question and I can understand your frustration.  The use of BMI to determine whether you are of ideal, over or obese body weight can be fraught with challenge as it doesn’t take into account habitus, muscle bulk etc.  Some elite athletes are considered obese based on their BMI alone but for them the weight is predominantly muscle.  For the average person, however, BMI remains a useful tool.
Body weight is a balance between output and intake.  If your intake is greater than your output, the likelihood is that you will put on weight.  While this seem quite disheartening, there can be a number of other factors that come into play, such as your physiology and potential medical conditions.  Some people find that they are able to lose weight more with certain exercises than others and for some it’s about combining different types of exercise to optimise outcomes.
Hormone conditions, such as thyroid and adrenal diseas can also affect your weight and it maybe that there is an underlying issue with this.
Without getting too disheartened, why don’t you seek some help with your goals.  It might be work visiting a sports clinic that has physicians, dietitians and physiotherapists available to help with your diet, exercise plans and conditioning.  Usually a combined approach is helpful.  Once you have started to see the benefits, you can then move onto a more general public gym or attend a program that you enjoy.
I hope this helps.
Dr Dinesh 

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

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