Inspired by an article by Giles Yeo, PhD, one of the smartest (and funniest) researchers I know.
We’ve long been told that managing weight is simple: eat less, move more. But anyone who’s ever struggled with hunger knows it’s not that easy. In a recent article for BBC Science Focus, geneticist Giles Yeo offers a powerful reminder: weight regulation is governed by biology as much as behavior—and for many people, genes play a starring role.
Your Genes, Your Appetite
While diet culture has trained us to blame weight on discipline, science tells a different story. Studies of identical twins raised apart show that body weight is 40–70% heritable—meaning that much of our size is written into our DNA, especially when it comes to appetite.
Yeo explains that genetics don’t just dictate our metabolism or how we store fat. More importantly, they influence how our brain perceives hunger, fullness, and reward. Think of appetite like a conversation between your gut and your brain. Hormones like leptin (which signals fullness) travel through the bloodstream and activate specific brain circuits, telling you when you’ve had enough. But in some people, that message doesn’t get through clearly.
It’s Not Just One Thing
Weight is complex. While some people are more genetically predisposed to feel hungrier or less full, others may be driven to eat more by emotional stress, disrupted sleep, or even social conditioning. That’s why, in my recent Wellness Wednesday webinar—Stress, Sleep, & Metabolic Health—I discussed another powerful (and underappreciated) driver of weight gain: chronic stress. When we’re under pressure, our cortisol levels rise, our sleep suffers, and our cravings for high-calorie comfort foods spike—all of which can work against our metabolic health.
The truth is, biology, environment, and behavior are all deeply intertwined. There’s no single “cause” of weight gain, and no one-size-fits-all solution.
Time to Rethink the Blame Game
One of the most liberating takeaways from Yeo’s work is that willpower is not the problem. For those with strong genetic drivers of appetite, hunger isn’t just a fleeting craving—it’s a chronic signal that their brain perceives as real and urgent. Fighting it isn’t about weakness; it’s about biology.
Thankfully, science is catching up. From new medications that target brain pathways to lifestyle interventions that reduce stress and improve sleep, we’re learning to address weight in more compassionate, individualized ways.
The Bottom Line
If you’ve struggled with weight, it may be time to let go of the guilt and recognize the many forces at play—from your DNA to your daily stress. Yes, lifestyle matters. But so do your hormones, your sleep, and how your brain interprets hunger and reward.
As Giles Yeo says, “It’s not about what you eat—it’s about why you eat.” And sometimes the answer starts in your genes... and is amplified by your life.