A Heat-Generating Gene Linked to Weight Gain (UCP1)

There are three main types of fat (adipose) tissue:

• White fat: this is what many people think of as “body fat.” This is the body’s primary form of energy storage; people with too much white fat are considered obese [R]
• Brown fat: also called “good fat”. Brown fat is burned to generate heat and maintain body temperature [R]
• Beige fat: when white fat starts working like brown fat and burns calories, it is called beige fat. White fat is converted into beige fat in a process called “browning” [R, R]

UCP1 (uncoupling protein 1) is mainly found in the mitochondria of brown and beige fat cells. It’s also called thermogenin because it helps generate heat by a process called non-shivering thermogenesis, which helps our bodies stay warm in cold environments [R, R, R, R, R].

Because it prevents excess energy from being stored as body fat (and instead turns it into heat), many researchers believe that UCP1 could protect against weight gain and obesity [R, R, R].

In this post, we’ll look into the UCP1 gene, which may be associated with weight gain and obesity [R, R].

Before we proceed, however, it’s important to note that there are many different genes that affect your metabolism and likelihood of being overweight — and UCP1 is only one of them! We will address more weight-associated genes in our upcoming posts.

If you believe that your genes are making it more difficult to lose weight, talk to your doctor about the information and strategies in this post.

The UCP1 protein diverts energy from being stored as fat and instead helps turn it into heat. Because of this, some researchers believe that UCP1 activity protects against weight gain and obesity.

One of the best-studied SNPs in the UCP1 gene is rs1800592 (also known as the “-3826 A>G” polymorphism). It helps determine how your body uses and stores the energy that you get from food [R].

There are two possible variants (alleles): ‘T’ and ‘C’.

The ‘T’ allele is linked to increased activity of the UCP1 gene. It’s associated with a higher resting metabolic rate, higher body heat production, and less weight gain. According to some researchers, this variant helps turn more of the energy from food into heat instead of body fat (white fat) [R, R].

Conversely, the ‘C’ allele is linked to decreased activity of the UCP1 gene. It’s associated with a lower resting metabolic rate, lower body heat production, higher weight gain, and a higher BMI. If less of the energy acquired from food is turned into heat, then more of it would get stored as body fat [R, R].

You can see your genotype for this SNP in the table below:

(Note that alleles are given in the “plus” orientation to match with your raw data. Scientific studies may report it in the “minus orientation” — so if you click through to our sources, you may see ‘A’ and ‘G’ alleles rather than ‘T’ and ‘C’ alleles, but this isn’t a mistake! To convert between the two, ‘C’ = ‘G’ and ‘T’ = ‘A’.)
 

The ‘T’ allele is associated with increased metabolic rate and higher body heat production. The ‘C’ allele, by contrast, is associated with decreased metabolic rate and increased weight gain, body fat content, and BMI.

According to several studies, the ‘C’ allele (and especially the ‘CC’ genotype) is associated with increased weight gain as well as a higher chance of being obese [R, R, R, R, R, R, R, R].

For example, people with the ‘CC’ genotype were found to have lower basal metabolic rates than people with the ‘T’ allele. In other words, they burned less energy when resting. In fact, one study reported that ‘C’ carriers may burn as much as 200 fewer calories per day than people with the ‘TT’ genotype [R, R]!

Apart from burning less energy when resting, people with the ‘CC’ genotype also produced less heat when exposed to cold [R, R].

We all lose brown fat as we age. However, in one study, people with the ‘CC’ genotype had less brown fat at a younger age than people with the ‘T’ allele [R].

Finally, several studies link the ‘C’ allele and the ‘CC’ genotype to metabolic disturbances commonly associated with being overweight. In various studies, the ‘C’ allele has been associated with elevated blood pressure, greater insulin resistance, and higher LDL cholesterol and triglycerides [R, R, R, R, R, R].

Despite this strong body of evidence, additional research is required to determine whether the ‘C’ allele is the direct cause of these problems.

Researchers have found a potential link between the ‘C’ allele at rs1800592 and slower resting metabolism, weight gain, and obesity. According to some studies, the ‘C’ allele is also associated with high cholesterol and insulin resistance.

Fun fact: worldwide, about 30% of people have the ‘TT’ genotype, which is associated with higher resting metabolism and increased heat production. But this genotype is much more frequent in Europe, where 58% of people have it! Many researchers believe that the UCP1 gene and the rs1800592 SNP are in part responsible for human adaptation to colder climates [R].

Sure enough, a study of 52 populations worldwide found that the ‘T’ allele was considerably more common in colder regions [R].

However, although today we consider the ‘T’ allele beneficial in terms of its potential effect on body weight, this allele is essentially linked to lower metabolic efficiency. In other words, people with this allele may “waste” more of the energy that they get from food on generating body heat [R].

Some researchers have suggested that the more efficient ‘C’ allele may be advantageous when food is scarce and the climate is warm [R].

The ‘T’ allele is more common in colder climates, where increased body heat production is advantageous.