Body mass index

Body mass index reflects weight relative to height. This score estimates your inherited tendency toward a higher or lower BMI, which diet and activity strongly modify.

What this BMI score reads

This is PGS000770, a 231-variant score assembled by de Toro-Martín and colleagues in 2019 for the Quebec Family Study, drawing on BMI GWAS data from 884,136 people, about 77% of European ancestry. It includes variants that reached genome-wide significance plus some with suggestive evidence.

Its largest single weight belongs to the FTO variant rs9939609, the most famous common obesity variant, which this site also reads on its own page.

How well it predicts BMI

The score explained about 3.2% of the variation in BMI in the study's validation sample. For obesity as a yes-or-no outcome, people in the top fifth of the score had 4.77 times the odds of obesity compared with the bottom fifth, with an area under the curve of 0.66.

Those odds sound impressive until you see the sample: 177 people, 50 of them with obesity, in a study of related family members. Estimates from samples that small are imprecise, and the honest summary is the variance figure: this score accounts for a few percent of why people differ in BMI.

How to read a high or low score

A high percentile describes a leaning, not a destiny, and the leaning is modest. Studies of genetic risk and lifestyle in far larger samples consistently find that physical activity and diet quality shift weight within every genetic stratum.

BMI is also a crude measure. It does not distinguish muscle from fat or account for where fat sits, which is why waist measurement adds information a BMI-based score cannot.

What this score does not capture

Monogenic obesity, caused by variants in genes such as MC4R, LEP, LEPR and POMC, produces severe obesity from early childhood and is diagnosed by sequencing, not by a common-variant score. Obesity that began in early childhood, is extreme, or comes with developmental features is a reason to ask a clinician about that possibility.

The environmental side is missing entirely, and it is large: food availability and cost, sleep, medication effects including several antipsychotics and steroids, thyroid disease, and physical activity through the day.

Ancestry and accuracy

The source GWAS was about 77% European ancestry, and the score was developed and validated in a French Canadian family cohort. That is a narrow base, and body composition, fat distribution and their genetic correlates differ substantially across populations.

Variants in this score you can read on their own

This score includes variants that this site also explains individually, where you can see what each genotype means on its own: BDNF memory & stress variant (Val66Met) (rs6265) · Body mass (BMI) tendency (rs9939609) · Type 2 diabetes risk (rs7903146).

How much of this score your file covers

230 of the published score's 231 variants are present in a standard consumer DNA file (100%). The remaining one cannot be read from one, so a result computed here approximates the published score rather than reproducing it.

Common questions

Does a high BMI polygenic score mean I cannot lose weight? No. The score explains a few percent of BMI variation, and studies of physical activity and diet find effects within every level of genetic risk. It describes a starting tendency, not a limit.

How is this different from the FTO result? FTO is the single largest common variant for body weight and has its own page here, where you can read your genotype directly. This score includes it as its largest ingredient among 231 variants, so it gives a broader but blurrier picture.

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