Chris van Tulleken's episode on Diary of a CEO became one of the most-watched health episodes in the show's history — and for good reason. The infectious disease doctor and author of Ultra-Processed People sat down with Steven Bartlett to expose how the food industry is engineering products that hijack your brain, destroy your gut, and shorten your life. This is everything you need to know.
This episode sent shockwaves through the health and wellness space. If you've ever wondered why you can't stop eating certain foods, van Tulleken's research provides the disturbing answer. For more health-focused episodes, check out our best Diary of a CEO health advice roundup.
Van Tulleken begins by defining what ultra-processed food actually is — and it's not what most people think. UPF isn't just "junk food." It's any food that contains ingredients you wouldn't find in a domestic kitchen: emulsifiers, stabilizers, humectants, flavour enhancers, and modified starches.
"If a product contains an ingredient you wouldn't find in your grandmother's kitchen, or if it's wrapped in packaging with a health claim on it, it's almost certainly ultra-processed."
— Chris van Tulleken, Infectious Disease Doctor & Author of Ultra-Processed People, on Diary of a CEO
The alarming statistic: over 60% of the average British diet is now ultra-processed food. For children and teenagers, that number climbs even higher. Van Tulleken argues this isn't a matter of willpower — the food is literally designed to override your body's natural satiety signals.
One of the most powerful moments in the episode comes when van Tulleken explains the neuroscience behind food addiction. He describes how ultra-processed food activates the same reward pathways in the brain as addictive substances.
"These foods are not food in any traditional sense. They are industrially produced edible substances designed to be over-consumed. The companies know exactly what they're doing."
— Chris van Tulleken, Infectious Disease Doctor & Author, on Diary of a CEO
Steven Bartlett was visibly shaken during this segment. He admitted to looking at his own diet differently after hearing van Tulleken's research. The conversation touched on how flavour scientists use "bliss points" — precise combinations of salt, sugar, and fat that maximize consumption while minimizing feelings of fullness.
Van Tulleken famously put himself on an 80% ultra-processed diet for four weeks as a controlled experiment. The results were devastating:
"After just four weeks, my brain had physically changed. The connections that formed looked like the early stages of addiction. And I'm a doctor — I knew what I was doing to myself, and I still couldn't stop."
— Chris van Tulleken, Infectious Disease Doctor & Author, on Diary of a CEO
Van Tulleken doesn't hold back when discussing the food industry's tactics. He draws direct parallels to the tobacco industry, arguing that food corporations use the same strategies: fund misleading research, lobby against regulation, and blame consumers for their own poor choices.
The conversation reveals how "healthy" labels — low-fat, high-protein, wholegrain — are often marketing tools slapped onto ultra-processed products. Van Tulleken urges listeners to ignore front-of-pack marketing entirely and focus on the ingredients list.
Despite the alarming information, van Tulleken is careful to offer practical solutions. He's not advocating for a perfect diet — he's advocating for awareness.
"I'm not saying never eat ultra-processed food. I'm saying: know what it is, understand what it does, and make an informed choice. Right now, most people have no idea what they're eating."
— Chris van Tulleken, Infectious Disease Doctor & Author, on Diary of a CEO
His practical advice includes:
At the end of the episode, Steven shared that this conversation genuinely changed his perspective on food. He described it as one of the most important health conversations he's had on the podcast — a sentiment echoed by millions of viewers.
The episode has since become a cultural touchstone, cited by nutritionists, doctors, and health influencers worldwide. It's proof that Diary of a CEO at its best can change how people think about their daily choices.
For more insights on health and wellness from the podcast, explore our guides on gut health and nutrition advice and Matthew Walker's sleep advice. You can also browse all best Diary of a CEO episodes.
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