Dr Len De Nys, a postdoctoral researcher and lecturer in physiotherapy at the Vrije Universiteit Brussel (VUB), is set to release his book "Waar rook is, is vuur" in early March. In it, he explores the impact of chronic inflammation and how a healthy lifestyle can help combat it. His popular podcast, Lifestyle as Medicine, has already featured interviews with numerous medical experts. But Len also speaks from personal experience—the consequences of chronic back pain profoundly changed his life.
How did this book come about?
“Ten years ago, I started working as a physiotherapist, but I soon began suffering from chronic back pain. As a result, I had to give up volleyball and eventually even took a year off work. The pain was accompanied by periods of depression, digestive issues, and tendon inflammation throughout my body. I consulted countless specialists, underwent scans, received spinal injections, and took anti-inflammatory medication—yet nothing provided lasting relief.”
“It was only when I started researching on my own that I realised my symptoms weren’t isolated but had an underlying cause: chronic inflammation, heavily influenced by my lifestyle. That discovery changed everything. I altered my diet, sleep habits, and exercise routine. I discussed my findings with colleagues and gradually began applying this knowledge to my patients—initially hesitantly, through occasional lectures, but later as the central theme of my doctoral research on lifestyle, stress management, and healthy ageing. At some point, I found myself being called an ‘expert’—not because I had discovered a miracle cure, but because I was addressing the root of the problem.
"Waar rook is, is vuur" is the result of that journey—a book about what I’ve learned, backed by scientific research and practical experience. And the best part? I now feel fitter and more energetic than ever. This book is here to help others find the same path.”
Dr Len De Nys
"Health Is Not One-Size-Fits-All"
When do we talk about chronic inflammation?
“You have acute inflammation, like when you cut your finger. Your body reacts immediately by sending inflammatory cells to the wound, fighting off pathogens, and beginning the healing process. This is a useful, temporary response—like a small fire that’s quickly extinguished. Chronic inflammation, however, works differently. Instead of a short-term reaction, it’s a persistent, low-grade immune response that affects the entire body. Rather than a controlled healing process, there’s an ongoing, smouldering inflammation—like a slow-burning fire that gradually damages cells and organs. Because this process often goes unnoticed, it can continue for years, laying the groundwork for serious health issues.”
“In the Western world, aside from accidents, the five leading causes of death are cardiovascular disease, cancer, diabetes, obesity, and dementia. What do they all have in common? Chronic inflammation plays a key role in each of them. It contributes to atherosclerosis, stimulates the growth of cancer cells, disrupts insulin regulation, triggers metabolic imbalances related to obesity, and accelerates neurodegeneration in the brain. The good news? You can put out this smouldering fire—and it all starts with a healthy lifestyle.”
Is the medical world acknowledging this issue?
“Research is increasingly highlighting chronic inflammation as an underlying factor in many diseases. That’s why scientific studies often measure inflammatory markers, such as CRP and interleukins, to better understand and reduce inflammatory processes. However, clinical practice has been slow to catch up. Many healthcare professionals still focus on treating symptoms and acute conditions, while chronic inflammation as a root cause is often overlooked. This is partly because it remains a relatively underexplored area in conventional medicine, where lifestyle is primarily seen as a preventive measure—helpful in avoiding disease but less so as an active therapeutic tool.”
“But now that we understand a healthy lifestyle not only prevents disease but also actively reduces chronic inflammation, there’s enormous potential for treatment. Unfortunately, this awareness is still underutilised in practice—when, in fact, it could be the key to better healthcare and recovery.”
"Lifestyle is still underrepresented in our university Curricula—though Some professors are making progress"
How do you adapt your lifestyle?
“It really comes down to what your grandmother already knew: eat healthily, stay active, get good sleep, and manage stress. However, the exact approach depends on your individual circumstances. For a healthy person, the 80-20 principle can be a good starting point: 80% of the time, you make conscious, healthy choices, while the remaining 20% allows for enjoyment without guilt. This creates a sustainable balance and helps prevent obsessive behaviour around food and exercise.”
“For those with chronic illnesses, autoimmune diseases, or other inflammation-related issues, a more targeted approach is needed. It’s not just about ‘living healthier’ but actively reducing inflammation through diet. That means eating anti-inflammatory foods rich in omega-3 fatty acids (such as oily fish and flaxseeds), polyphenols (like turmeric, green tea, and dark berries), and fibre (from vegetables, legumes, and whole grains) to support the immune system. At the same time, inflammatory foods should be avoided—this includes highly processed foods, sugars, trans fats, and potential triggers like gluten or dairy, depending on individual sensitivities. In addition, movement should be carefully adapted, while sleep and stress management must become top priorities.”
“Health isn’t one-size-fits-all. The key is understanding your own body and adjusting your lifestyle to support both recovery and prevention.”
So why don’t we just do it?
“The environment we live in plays a major role in shaping our lifestyle choices, often leading to less healthy habits. Most of us have sedentary jobs. At the same time, life is made ‘easier’ for us—you no longer need to wash up, cook, or even move much at all.”
“Inflammation is influenced by genetic factors, gender differences, and lifestyle. The latter is the one you can control. That means looking at the habits that contribute to your overall health. In my case, I exercised daily and played beach volleyball at a national level. But I drank too much alcohol, which affected my sleep. I didn’t feel good in myself, my gut microbiome was in bad shape because I wasn’t eating enough fibre, and I consumed too many processed foods.”
“Both personally and professionally, I can finally do what I’ve always wanted to do. Strangely enough, I have my chronic back pain to thank for that.”
Has the medical sector evolved enough?
“In my podcast Lifestyle as Medicine, I interviewed one of Belgium’s leading neurologists, VUB Professor Steven Laureys, who strongly advocates meditation. Ten years ago, that would have been dismissed as ‘hippy nonsense’. But there’s a shift happening—more and more doctors and health professionals recognise that we need to move towards lifestyle medicine. However, when I look at how this is integrated into medical education, we’re still taking very small steps. Lifestyle is still not embedded deeply enough in university curricula, though fortunately, some professors are pushing for change.”
How has your personal situation evolved?
“During the period when I was forced to stop playing sports, my relationship also ended. And rightly so—I wouldn’t have wanted to be around me back then either. Now, I’m very happy with my wife and physically fitter than ever. Both personally and professionally, I can finally do what I’ve always wanted to do. Strangely enough, I have my chronic back pain to thank for it all.”
‘Waar rook is, is vuur’
Waar rook is, is vuur: Everything you need to know about the hidden dangers of chronic inflammation and how to reclaim your Health by Dr Len De Nys is published by Borgerhoff & Lamberigts.
This book reveals the often-underestimated impact of chronic inflammation—a silent threat that can go unnoticed for years, gradually causing significant harm. Unless you take control in time.
Health scientist and physiotherapist Dr Len De Nys not only shares his personal battle with chronic pain but also offers a fresh perspective on how simple lifestyle changes can make a world of difference. In a clear and scientifically grounded way, he explains how this ‘hidden fire’ develops—and, more importantly, how you can put it out before it’s too late.
