With the acceptance of being a little overweight

I hear of people saying they were born morbidly obese and it was genetically passed on. I'm aware being so obese leads to countless health issues, yet we have people defending fat shaming and the likes. Is the excuse of having 'obese' genetics scientifically justified? Do people have genetics that make them ridiculously fat? Alongside, would this simply be down to the diet of the person from a young age?



3 Answers 3


It is certainly a very difficult question to answer.

There are some genetic disorders that can predispose individuals for becoming obese: https://www.ncbi.nlm.nih.gov/pubmed/18230893

There are also evidence of epigenetic influences on obesity: http://www.nature.com/nrendo/journal/v12/n3/full/nrendo.2016.18.html

Typically each case of obesity is caused a combination of both genetics, epigenetics and lifestyle: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3873060/

However also keep in mind that obesity is a fairly recent problem and as such the genetic changes are likely minimal between the 1980 and 2008 populations sampled by WHO: http://www.who.int/gho/ncd/risk_factors/obesity_text/en/ A doubling in the prevalence of obesity in the two populations are most likely caused by changes in lifestyle and the availability of food, rather than genetic changes as the time frame is so short.

So to sum up: Morbid obesity caused by currently unfavorable genetics exists but is very rare. People can be genetically and epigenetically predisposed for developing obesity, which when combined with certain lifestyles can further increase the risk of becoming obese.


Genetics is not a yes or no question, every gene is affected by its environment and often the environment is influenced by other genes as well. Are their genes that can make you more likely to be obese, Yes. There are also genes in our gut flora that influence it as well. How these genes are expressed may or may not be influenced by environmental factors. It likely varies by the gene. And of course no gene will make you obese in a absence of calories, but they can greatly change the number of calories you need to become obese.

Morbidly obese is a tricky phrase, since the BMI is not actually based on scientific measure of health. Many athletes score very high on the BMI. So you may want a more concrete definition to work from.


It's a myth that obesity is mostly caused by genes. Yes, there are many genes that predetermine your apetite but when a baby is born obese, it's not a matter of genes but a matter of the mother's health and diet. And because till the birth, the fetus shares a single bloodflow with the mother, it gets everything the mother has in her blood. Thus, some babies are born obese, some are born addict.

Indeed, there are papers showing that there's a higher chance for the newborn to die during birth, even though you can't always say what was the main cause of death (also it depends on what you connect with obesity).

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    $\begingroup$ It'd be great if you could link to a peer-reviewed paper instead of livescience.com small article $\endgroup$
    – Remi.b
    Dec 11, 2016 at 16:22
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    $\begingroup$ Down voted this answer due to poor sources. Also the point regarding newborn obesity is certainly true, but the strong dismissal of the influence of genetics on obesity is not scientifically correct! I have provided a more balanced and better documented answer, that also focuses on the effect of lifestyle on obesity. $\endgroup$ May 15, 2017 at 3:44

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