As the new year prompts many to set health goals, a leading scientist underscores that the struggle to lose weight is often rooted in biology, not just a lack of willpower. Dr Giles Yeo, a professor of molecular neuroendocrinology at the University of Cambridge, has detailed to The Independent how an individual's genetic makeup plays a decisive role in their relationship with food and body weight.
The Genetic Blueprint of Appetite
Dr Yeo states that more than 1,000 genes are involved in regulating our feeding behaviour, directly impacting body weight. He explains that people are driven to eat for complex reasons, making it inherently harder for some to refuse food and manage their weight. This genetic predisposition means that for two people following an identical diet and exercise regime, results can vary dramatically.
One of the most critical genes identified is the melanocortin 4 receptor (MC4R), a brain receptor key to regulating appetite and energy balance. Since 1998, scientists have known that mutations in this gene are linked to obesity, often beginning in childhood. Dr Yeo reveals that approximately 0.3% of the general UK population carries a mutation in the MC4R gene, equating to over 200,000 people.
"More than 200,000 people within this country will potentially have a broken fat sensor," Dr Yeo said. "What that means is they think they have less fat when they actually do." The impact is substantial: by age 18, individuals with this mutation are, on average, nearly 18kg heavier—or five BMI points higher—than those without it.
Beyond Genetics: The Environmental Factor
While genetics load the gun, Dr Yeo emphasises that our environment pulls the trigger. He points to the Health Foundation's 2025 report, which found around 60% of UK adults are now overweight, a figure that has risen steadily. Our 'obesogenic' environment—characterised by abundant processed foods and sedentary, office-based jobs—is a major driver.
"Genetics explains why some people find it difficult to say no to this energy-rich environment that we have," Dr Yeo notes. Consequently, narratives focusing solely on personal willpower and self-control are unhelpful for public health. Instead, he advocates for systemic change, such as fixing the food environment through measures like the new government ban on junk food advertising online at all times and on TV before 9pm.
Taking Control of Your Personal Food Environment
Recognising that individuals cannot single-handedly transform supermarket offerings, Dr Yeo advises people to focus on the environment they can control: their own homes. The first step is honest self-reflection. "If you're trying to lose weight, you need to be honest with yourself about why you're eating," he advises. "Some people eat because they're hungry, other people eat because they're stressed."
Understanding your personal triggers and food weaknesses allows you to strategically reduce the presence of those items in your household. This practical approach empowers individuals to work with their biology, rather than fighting against it with sheer willpower alone.
