Why some people find it harder to lose weight, according to science

The start of a new year is a time when tradition dictates we set goals for the months ahead.

For many, this can mean thinking about healthier diets and shedding the pounds, especially after indulging during the festive period.

But while eating well and moving more is a great place to start, weight loss isn’t necessarily all about willpower and self-control. Scientists have proven that some find it easier than others to drop the pounds, and it’s all down to your genetics.

Dr Giles Yeo, professor of molecular neuroendocrinology at the University of Cambridge and author of Gene Eating, spoke to The Independent about how your genetic makeup can influence your attitude towards food, and therefore your weight.

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“Simply put, some people are driven to food for a myriad of different reasons,” he said. “Hence they find it more difficult to say no, they eat more, and they’re going to be larger than someone else.

“So for the same reason, some people find it more difficult to lose weight.”

Dr Yeo said there are “over 1,000 genes” that are involved in our feeding behaviour, and that these have a clear impact on our body weight. One of the most researched is the melanocortin 4 receptor (MC4R) - a key brain receptor that helps regulate appetite, body weight, and energy balance.

In 1998, scientists first discovered that genetic mutations in this receptor are linked to obesity as early as childhood. Dr Yeo said today, it is known that about 0.3 per cent of the general population has one of a variety of mutations in this gene. When extrapolated to the UK population, this is more than 200,000 people.

“More than 200,000 people within this country will potentially have a broken fat sensor,” he said. “What that means is they think they have less fat when they actually do.”

Dr Yeo explained how the mutation can have a huge and proven impact on people’s body weight. “When people with this mutation reach 18 years old, they are on average nearly 18kg heavier than those without,” he said. “That’s five BMI points.”

Significantly, out of the population who struggle with health issues related to “severe obesity” and are treated in a clinic, the percentage with an MC4R mutation jumps to anything from 2 per cent to 10 per cent, he said.

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“So if you go to the population with severe obesity, the number of people with the mutation really jumps,” he added.

Hunger cues are another factor that can influence how easy people find it to lose weight, according to Dr Yeo. He told The Independent broadly the brain needs two pieces of information to influence your hunger cues - how much fat you have, and what you are currently eating and have just eaten.

It gets these through sensing hormones from your gut and intestines - but people’s brains sense these differently, hence why some people feel hunger cues differently from others.

But Dr Yeo pointed out that genetics does not tell the whole story. According to the Health Foundation’s 2025 report, around 60 per cent of UK adults are overweight, with this number rising steadily over the last decade.

He said both our food environment - essentially the choice of food available to us and the accessibility of processed foods - and our built environment, such as the prevalence of office-based jobs, are also major contributors to why some people struggle to lose weight.

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“That has driven the prevalence of obesity, but not everyone has obesity,” he said. “Genetics explains why some people find it difficult to say no to this energy-rich environment that we have.”

Narratives of self-control and willpower can therefore be “unhelpful” in conversations about how to help society as a whole become healthier, according to Dr Yeo.

Instead, he believes we need to “fix the food environment” - something he said a new government ban on junk food advertising online at all times and on television before 9pm can help with.

But Dr Yeo acknowledged radical transformations to our supermarket offerings are not something individuals have the power to choose. Instead, he encouraged people to focus on the food environment they can control - their own homes.

“If you’re trying to lose weight, you need to be honest with yourself about why you’re eating,” he said. “Some people eat because they’re hungry, other people eat because they’re stressed.

“Then you need to know what you like to eat. What is your weakness? If you understand what you like to eat under those circumstances, you can try and reduce those particular foods within your household.”