On Wednesday evening, the Medical Society were honoured to present Dr Giles Yeo MBE, Professor of Molecular Neuroendocrinology at the Medical Research Council and Scientific Director of Genomics at the University of Cambridge, for their first meeting of 2025. His talk, titled ‘Is Obesity a Choice?’, attracted many boys, staff, and students from partner schools. This interest is largely due to the relevance of the topic in today’s news, especially as a result of the rise in popularity of the weight-loss drug Ozempic. Despite the complex topics covered, the audience remained engaged throughout – thanks to Dr Yeo’s lively and accessible speaking style.
Dr Yeo explained how the body regulates levels of hunger and weight. Fat tissue releases a hormone called leptin, which signals to the brain when enough energy has been stored. When leptin levels are high, the brain tells the body to eat less and burn more energy. When leptin is low, such as during fasting, the brain responds by increasing hunger and slowing metabolism to conserve energy. However, in some cases, people’s brains stop responding to leptin properly, meaning they still feel hungry even when their bodies have enough fat stored. This issue, known as leptin resistance, can lead to overeating.
To illustrate how genetics can influence obesity, Mr. Yeo discussed a rare case where children with a genetic condition could not produce leptin at all. As a result, they were constantly hungry and gained excessive weight. When given leptin as a treatment, their appetite reduced, and they started losing weight, proving to the audience that biology plays a key role in body weight regulation.
However, Dr Yeo outlined that for most people with obesity, the issue isn’t a lack of leptin but rather how the brain responds to it. Mr. Yeo made it clear that obesity is not simply a matter of willpower. While diet and exercise are important, factors like genetics, brain chemistry, and the modern food environment make weight management harder for some people than others. He compared genetics to a ‘hand of poker’, saying that while some people are dealt a more challenging set of genes, they can still make choices that help them maintain a healthy weight. He emphasised that obesity does not mean someone is lazy or lacks self-control – rather, it is a complex issue influenced by both biology and lifestyle.
The talk left the audience with a deeper understanding of the science behind weight gain and an appreciation for the challenges faced by those struggling with obesity.