Thinness is something that you inherit

Summary: Being thin is genetic

There is a genetic predisposition to being thin and avoiding putting on weight.

Slimness is, in part, the result of genetics

The study, published on January 24, 2018, confirmed that being thin, just like being fat, is due to the genes you inherited from your parents.

So slimness, just like obesity, is a matter of chance and is strongly influenced by the mix of genes that you received from your mother and father.

Obesity, which has been studied in more detail can be caused by over 250 common yet low-frequency genetic loci (loci is plural for locus, is a "marker," a specific physical location of a gene within a chromosome.)

Thinness, as defined by the World Health Organization, encompasses individuals whose body mass index or BMI is equal or lower than 18 kg⁄m2.

We discuss Body Mass Index on our "BMI" webpage:

The researchers took a group of 1,600 thin yet healthy individuals and compared their genetic makeup with another group of 2,000 severely obese subjects.

The comparison showed that:

• Obese people had a higher chance of having genes linked to being overweight.
• Thin people had fewer genes linked to obesity and therefore a lower risk of gaining weight.
• "Skinny" individuals and obese people share several genetic risk loci, but slim people had genetic changes in some genes linked to obesity.

Food for thought

If you are slim, try to be less critical and judgmental about overweight people, you were lucky to inherit the "good" combination of genes, while they got the "bad" combo.

If you are overweight, don't despair, you can take action and work on your body weight: exercise and a balanced low-calorie diet can help you lose weight and keep it off. You are not predestined to being overweight.

The "skinny gene"

Research by Orthofer et al. published in June 2020 identified the anaplastic lymphoma kinase gene (ALK) as a possible thinness gene. They also found that ALK increases energy expenditure, burns fat, and reduces weight gain (2).

References and Further Reading

(1) Riveros-McKay F, Mistry V, Bounds R, Hendricks A, Keogh JM, Thomas H, et al. (2019). Genetic architecture of human thinness compared to severe obesity. PLoS Genet 15(1): e1007603. https://doi.org/10.1371/journal.pgen.1007603

(2) M Orthofer, et al. (2020). Identification of ALK in Thinness. Cell Vol 181:6. pp1246-1262. June 11, 2020. DOI:https://doi.org/10.1016/j.cell.2020.04.034