Genes may hold the secret to how easily you gain or lose weight

Weight gain isn’t just about what you eat – it also depends on your genes. That’s the message from a large study out of Estonia that examined more than 200,000 people to understand how DNA influences body weight.

This isn’t a new question. Scientists have searched for an “obesity gene” for years, but that idea has mostly fallen flat. Instead, this new research shows it’s not just one gene at work.

Obesity is more like a team effort among many genes, each contributing just a little. Add in environment, lifestyle, and age, and the picture gets even more complicated.

Early signs in body weight

Scientists examined body mass index (BMI) data from 204,747 Estonian adults. BMI is an easy method to compare height and weight. It’s not perfect – it doesn’t account for anything like muscle or age – but it provides a good snapshot of weight trends in a population.

They zeroed in on each person’s earliest recorded BMI. That’s because genes tend to show their strongest effects early on.

“As people grow older, environmental factors, such as diet, accompanying illnesses, and lifestyle, begin to play a greater role,” said Erik Abner, functional genomics researcher at the University of Tartu and author of the study.

Estonia’s DNA tells a story

Using a technique called a genome-wide association study (GWAS), the researchers scanned millions of genetic markers to spot differences linked to BMI.

What made this study stand out was its use of Estonia’s own population-specific genetic data. That enabled the researchers to detect smaller effects that may not be captured in more global studies.

Although Estonians are genetically similar to other Europeans, the research revealed subtle differences in how certain genes contribute to weight and appetite.

Hunger written in our genes

One of the more interesting findings involved a gene called MC4R. A particular version of this gene, found in 3.5 percent of Estonians, is linked to lower BMI. People with this version generally feel full faster and eat less.

On the other hand, a variant within a gene named POMC, occurring in only 0.85 percent of Estonians, appears to have the opposite effect.

This version influences how the brain produces appetite-suppressing hormones. Individuals with it feel full later and eat more. In women, this can result in approximately 6.6 pounds of additional weight. In men, it’s roughly 2.2 pounds.

Abner made an interesting connection to dogs – specifically Labrador Retrievers. A similar genetic variant is known to make Labs more food-motivated and prone to weight gain. The Estonian POMC variant seems to have a similar effect in humans.

Appetite begins in the brain

The study also found links between BMI and two other genes – ADGRL3 and PTPRT. These genes help the brain send and receive signals.

They’ve previously been tied to attention and learning disorders. Now, they also appear to influence how the brain controls appetite.

The researchers think these genes may affect how the brain manages hunger hormones. If that’s true, they could eventually be targets for new obesity drugs.

Genes could tailor weight-loss plans

Weight-loss treatments have mostly taken a one-size-fits-all approach, but the truth is, bodies don’t all respond the same way.

Two people might follow the same diet and exercise routine, but if their genes affect hunger differently, they won’t see the same results.

These findings suggest that treatment could work better if it’s tailored to the individual. Instead of trial and error, doctors could eventually use genetic info to choose what’s most likely to work for each person.

The researchers are now starting a new study to see how today’s obesity drugs – like semaglutide – affect people with certain genetic traits. Since the drug targets hunger hormones, its effects might vary depending on someone’s DNA.

Obesity rates are rising in Estonia and around the world. This kind of research could help slow that trend, not with blanket advice, but with personalized medical tools based on how each body works.

The full study was published in the journal Nature Communications.

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