If you’ve been struggling to lose weight and can’t quite figure out why, Dr. Giles Yeo might have the answers you’re looking for. Whether you’re curious about why cravings for dinner hit right after a filling lunch, or why those stubborn pounds seem to keep coming back, he’s the expert to consult.
Dr. Yeo, who has been delving into the genetics of obesity for over three decades, is a professor at the University of Cambridge and leads a program at the MRC Metabolic Diseases Unit. During our chat, he casually admits that, like many, he constantly thinks about what he’ll eat next, even just moments after finishing his meal. He jokingly adds that he’s probably due to lose a bit of weight—around a stone or a stone and a half, according to his wife.
Beyond his research on how the brain regulates food consumption and the effects of GLP-1 medications, Yeo has authored books like Gene Eating and Why Calories Don’t Count, in addition to presenting science documentaries for the BBC. His newest project, The Hunger Game, which premiered recently, is a five-part series on Radio 4 that investigates the emergence of weight loss drugs, their health impacts, and the true nature of obesity—spoiler alert: it’s not merely a moral failing or a lack of willpower.
Dr. Yeo views obesity as a disease rooted in brain function. Interestingly, the World Health Organization shares this view. However, he points out a common misconception: many people equate obesity solely with excess body weight, leading to confusion about labeling it as a disease. “A clearer perspective,” he says, “is recognizing obesity as carrying too much fat to the point that it negatively affects your health.” This raises another question: why are some heavier individuals healthy while some who appear thin may struggle with conditions like type 2 diabetes? Yeo attributes this variance to individual differences in fat storage capacity.
He goes on to explain how our genetic make-up influences our relationship with food. “Some individuals have brain mechanisms that drive them to seek food more,” he says. This genetic predisposition can determine how we respond to our hunger cues based on energy reserves. He notes that our brains require both short- and long-term signals about our energy levels—short-term data comes from the gut, while long-term information stems from our fat stores. If someone is storing more fat than their brain perceives, they might instinctively overeat to balance things out.
Dr. Yeo’s own family experience lends insight into health trends in younger generations. He shares that they encouraged their 24-year-old son, Harry, to use GLP-1s after he gained a considerable amount of weight during university. Harry, who enjoys good food but isn’t much for exercise, faced challenges in changing his habits. Now, after over a year on the medication, he has successfully lost the weight he gained.
What’s Dr. Yeo’s advice for those using GLP-1s? While the medication can aid weight loss, it can’t substitute for dietary changes. To truly improve health, individuals must also focus on eating better. For example, he helped Harry by providing a simple cooking setup with an air fryer and easy-to-make meals. Since then, Harry has started going to the gym, reinforcing the idea that losing weight can also make exercising easier.
Dr. Yeo remarks on the inherent difficulty of maintaining weight loss, particularly when a small gain seems to “lock” into a personal weight range. “If you find yourself a few pounds heavier with no clear reason, that might indicate your body’s set point,” he explains. The brain perceives a loss below this set point as a threat to survival, triggering hunger and a slower metabolism to bring weight back up—a frustrating cycle for many. Interestingly, individuals genetically similar to each other can end up needing different caloric intakes to maintain similar weights.
He mentions that while sustained weight gain can shift one’s range upwards—studies in mice suggest this occurs over extended periods—there’s no evidence the range can decrease. This complexity underscores the challenges faced by many individuals trying to manage their weight effectively.
On maintaining muscle while using GLP-1s or after rapid weight loss, Dr. Yeo stresses keeping a balanced diet rich in protein. This is essential because, unlike fats and carbs, our bodies do not store protein in an inert form—it’s all active. However, he cautions against excessive protein intake, which can lead to fat conversion and strain the kidneys. He suggests a moderate intake for the average adult, emphasizing that athletes or individuals with specific needs might require more.
In terms of combating weight regain after dieting, Yeo shares that exercise has a crucial role—not necessarily for weight loss, but for maintaining weight once it’s lost. Any form of activity can raise metabolism temporarily and, he insists, is key to offsetting metabolic slowdowns after weight reduction.
Yeo offers practical advice for feeling full without consuming more—primarily, incorporating high-fiber and nutrient-dense foods into the diet. Foods that digest slowly keep you feeling satisfied longer. He cites the Mediterranean diet as an example, emphasizing the importance of plant-based foods. Although increasing fiber intake is effective, it won’t work for everyone, so it’s not a one-size-fits-all solution.
That said, he insists that if someone really wants to lose weight, they should focus on enhancing both protein and fiber intake, as both come primarily from plant sources. The average UK intake of fiber is still low, so increasing it could provide significant benefits.
The Hunger Game: The Rise and Rise of Weight Loss Drugs is available now on BBC Radio 4 via BBC Sounds.
