rs1800592
Brown fat, the tissue that burns calories as heat
What this position does
Brown fat does something unique: it uncouples the process that normally makes energy and releases the result as heat instead. It is how a baby stays warm, it is far more active in people who spend time in the cold, and UCP1 is the protein that does the uncoupling.
Fat tissue. Shaped by cold. This is one of the variants that differs sharply between human populations, because something in the environment made one version worth having.
Cold
Staying warm costs energy. Populations that wintered in the north did it partly with tissue that burns calories as heat, which is much less useful in a heated building.
What changed: Industry, roughly the last two centuries. Indoor work, heated buildings, refined food, cheap salt and sugar, tobacco at scale, and a collapse in infectious disease. This is where most of the deals in your genome came undone.
Why it spread: a strong case, not settled. There is a clear signal of recent selection and a widely favoured explanation for it, which is not the same as a proven one.
Spiral Staircase, chapter 25: The Thermoneutral Trap Spiral Staircase is written by the same author as this site.
What each result means
| If you carry | What it means |
|---|---|
| No copies of the effect version TT | You have the higher-activity version on both copies Associated with more heat production from brown fat on average. |
| One copy CT | You carry one lower-activity copy Intermediate. |
| Two copies CC | You have the lower-activity version on both copies Associated with less heat production from brown fat, and in some studies with slightly greater weight gain over time. The effects are small and the studies disagree, which is why this is graded moderate. |
Worth knowing. Brown fat activity responds strongly to actually being cold. Behaviour moves this far more than genotype does.
How common each version is
| Ancestry group | C (the effect version) | |
|---|---|---|
| African | 73.4% | |
| American | 40.6% | |
| East Asian | 46.5% | |
| European | 23.7% | |
| South Asian | 39.4% |
1000 Genomes Project phase 3, via Ensembl, retrieved 2026-09-23. These groupings are coarse and flatten a great deal of internal diversity, particularly within Africa. A variant being common somewhere tells you where a piece of your ancestry probably comes from, and nothing else.
How many people carry each result
| Ancestry group | TT | CT | CC |
|---|---|---|---|
| African | 43 / 661 | 265 / 661 | 353 / 661 |
| European | 292 / 503 | 184 / 503 | 27 / 503 |
| East Asian | 139 / 504 | 261 / 504 | 104 / 504 |
| South Asian | 182 / 489 | 229 / 489 | 78 / 489 |
| American | 121 / 347 | 170 / 347 | 56 / 347 |
Counts of people, not modelled frequencies: every one of the 2,504 individuals sequenced by the 1000 Genomes Project phase 3, tallied by the genotype they carry. Deriving these from allele frequencies instead would assume random mating inside each group and undercount the homozygotes.
How to find out which you have
If you have taken a test with 23andMe, AncestryDNA, MyHeritage, Family Tree DNA, TellMeGen or Living DNA, this position is very likely already in the raw data file they gave you. You do not need another test.
One thing to watch if you look it up by hand: testing companies report some positions from one DNA strand and some from the other, and the file does not say which. Read the letters as they appear and you will get the opposite of the truth for some positions. Sequencings resolves that automatically.
Source
Coordinates and allele pair verified against Ensembl GRCh37. Direction of effect verified against VEP protein consequences or 1000 Genomes population frequency. Category: Population adaptation.
Where this fits
Common questions
What is rs1800592?
rs1800592 is a position in the UCP1 gene on chromosome 4. Brown fat does something unique: it uncouples the process that normally makes energy and releases the result as heat instead. It is how a baby stays warm, it is far more active in people who spend time in the cold, and UCP1 is the protein that does the uncoupling.
What does it mean if I have CC at rs1800592?
You have the lower-activity version on both copies. Associated with less heat production from brown fat, and in some studies with slightly greater weight gain over time. The effects are small and the studies disagree, which is why this is graded moderate.
What does it mean if I have TT at rs1800592?
You have the higher-activity version on both copies. Associated with more heat production from brown fat on average.
How do I find out my rs1800592 genotype?
If you have taken a home DNA test, this position is very likely in the raw data file you were given. Sequencings reads that file in your browser without uploading it, and resolves which DNA strand each position was reported from, which is the step most manual lookups get wrong.
This is reference information, not medical advice, and not a diagnosis. See the medical disclaimer. Category: Population adaptation.