No One Should Be Surprised That There Are Skinny Genes

Anyone who has ever seriously looked at the genetics of obesity should be well aware that body weight and size is a highly heritable trait.

As one may expect, this heritability extends across the entire spectrum of body size. Thus, if there are genes that explain obesity, then perhaps certain variations of these very same genes may do the exact opposite – i.e. promote “skinniness”.

In fact, we all  know these people, who appear to be highly weight-gain “resistant”, in that they can apparently eat all day without gaining a gram of body fat or simply find it very difficult to “overeat” even when surrounded by highly-palatable food.

Now, a study by Fernando Riveros-McKay and colleagues, published in PLOS Genetics, compares the genetics of thinness with that of severe obesity.

Using genome-wide association studies, the researchers not only show that the heritability of thinness was comparable to that of severe obesity but they also confirmed the existence of 10 genetic loci that had been previously associated with obesity (as well as an addition obesity and BMI-associated locus (PKHD1).

As there may well be non-genetic reasons for people to fall into the “thin” end of the size spectrum, the researchers were careful to only include individuals who appeared in good health and especially excluded individuals with anorexia.

Overall, these finding are consistent with animal studies that have also identified loci/genes associated with thinness/decreased body weight due to reduced food intake/increased energy expenditure/resistance to high fat diet-induced obesity, mechanisms that the authors hypothesise may also contribute to human thinness.

Clearly, further genetic and phenotypic studies focused on persistently thin individuals may provide new insights into the mechanisms regulating human energy balance and may uncover potential anti-obesity drug targets.

@DrSharma
Edmonton, AB

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