No one could accuse Dr Nick Tiller of taking health and wellness issues lightly. In his latest book he recounts an occasion in which a friend asked him whether he was an extrovert or an introvert – the kind of question most of us would treat as small talk to pass the time. Tiller, though, took it seriously. What did she mean by those terms, he asked, hearing in response that it depended on whether he got energy from being around others, or not. OK, then: what did she mean by energy? ‘At this point,’ he writes, ‘she got frustrated and didn’t speak to me for the rest of her wedding. Which was awkward, since I was the best man.’

The wellness industry lacks many of the safeguards of mainstream medicine, and it’s putting us at risk

This anecdote characterises the tone of the book. Tiller sets himself up as a man who follows the science and evidence, and gets immensely frustrated when others don’t – especially when they use pseudoscience to play on our ingrained fears about health and mortality to sell us stuff. He is at his best in that crusading mode. At one point he reveals how he was approached by a company with an eye to recruiting him for ‘stealth marketing’ – the effort to persuade experts who appear across the media to drop certain key words that might direct the public to a product while avoiding directly naming it. The result is a clever way to navigate rules on disclosure and advertising.

The section on nutritional supplements and vitamin pills, often mass-manufactured in China, is even more alarming. Some contain barely a fraction of the active substance they claim to, while others are adulterated. Certain herbal or homeopathic pills for insomnia are laced with pharmaceutical sleeping medications. Supplements to help you gain muscle mass secretly contain steroids. The wellness industry lacks many of the safeguards and controls of mainstream medicine, and it’s putting us at risk.

For those who are already signed up to his crusade, Tiller is a convincing and entertaining guide, often indignant in the name of a cause he clearly sees as righteous. But if he’s trying to convince people who are tempted by the health and wellness industry, realistically this book is not for them. Tiller’s tone is so strident and his frustration so palpable that anyone who gives the time of day to these ideas is likely to bounce right off. The title alone is enough on that front.

The reality of dietary and exercise advice is boring: eat a broad diet, don’t eat too much, cut back on red meat and build moderate exercise into your routine. Do that and you may live longer than you would otherwise, and you’ll probably lose weight if you’re obese. It’ll take months, and you’ll have to keep it up for the rest of your life.

That’s hardly a great sales pitch, even if it’s the only one that actually works. No wonder fad diets, miracle supplements and magic devices are more tempting. Tiller is ultimately left trying to do what doctors and dieticians have done for decades: give us the same dull advice and hope this time we’ll listen. Trying the same thing and expecting different results, though, isn’t exactly the best demonstration of the scientific method.

This makes it all the more frustrating that Tiller seems unexcited by recent developments such as GLP-1 weight loss drugs like Wegovy and Mounjaro. He avoids scaremongering, but is extremely cautious as to their potential. We would do better, he insists, if we just stuck to the longstanding advice – ignoring the fact that obesity has continued to escalate over the decades during which that advice has been endlessly repeated.

His devotion to the evidence has other blind spots, too. His long list of villains inevitably includes social media and online advertising – an area I know far better than nutrition, and one in which he seems to have accepted every doubtful marketing claim, even if only to rail against it. He confuses his terminology and vastly exaggerates the effectiveness of online advertisements, showing none of the scepticism he deploys so well elsewhere – maybe because, in this case, the exaggeration serves his argument. It is perhaps a useful reminder that critical thinking can only get us so far. However well-trained we are, we will never escape our biases.

The Health and Wellness Lie is a timely and often sharp investigation of a multi-billion-dollar global industry. But, ultimately, it is also yet another reminder that we should all just eat our greens.