Different people need different approaches. Some benefit from more structure, others from flexibility. Increasingly, I’ve also come to see the importance of spiritual recovery, which involves addressing the deeper human need for connection and meaning.
David Wiss, PhD, RDN, FMCP, is a functional medicine clinician and mental health researcher who specializes in identifying the biological root causes that conventional care often misses—because most people aren’t treatment-resistant; they’re just undertested. His work is grounded not only in rigorous science but in a deep respect for the healing intelligence encoded in living systems. Dr. Wiss has authored more than 30 peer-reviewed publications, and his research has been cited in the New York Times, National Geographic, and the Washington Post. He is also Invited Faculty at the Nova Institute for Health.
Q: Your work intersects with nutritional psychology, eating disorders, and addiction recovery. Can you share your journey into this field and how you wove these different areas together?
David Wiss (DW): It’s been a wild ride, especially recently. The path I’m on now is not at all what I envisioned as a kid. In college, I was pretty lost, bouncing around between different departments and trying to figure out where I fit. I wasn’t fully committed to becoming an adult yet, and there’s definitely a countercultural thread in my story.
Ironically, my early exposure to nutrition didn’t go well. I took a class in college and ended up dropping it. It was very math-heavy—tracking calories, BMI—and it just didn’t resonate with me. That experience actually left me with a negative impression of the field for a while.
Things shifted in my mid-20s when I went through a major personal wellness transformation. My mental health improved dramatically as I focused on foundational habits like nutrition, exercise, sleep, sunlight, and hydration. That led me to ask deeper questions about identity and purpose, and ultimately drew me toward the healing arts. I went on to become a registered dietitian and earned a master’s in nutrition, motivated by a desire to be part of the solution.
But early on, I felt disillusioned with the field. My training seemed heavily influenced by corporate interests, particularly the food industry. That didn’t sit right with me, so I became involved in some renegade efforts to call out conflicts of interest.
I gravitated toward substance use disorder work because there weren’t many people integrating nutrition into that space. It felt like an opportunity to make a meaningful, novel contribution. That led to my master’s thesis and eventually to building my company, Nutrition in Recovery, which focuses on the intersection of nutrition and mental health.
Later, I pursued a doctorate in public health at UCLA, with a minor in health psychology. My training became very interdisciplinary—social science, biology, psychology, epidemiology—while I continued to deepen my independent work in nutrition, neuroscience, gut health, and functional medicine. I eventually became certified through the Institute for Functional Medicine.
More recently, I’ve become increasingly interested in psychedelic medicine. That wasn’t intentional at first, but rather emerged organically as patients and colleagues began sharing their experiences. Over time, I came to see functional medicine as a natural bridge between physical and mental health, and a compelling home for these emerging therapies.
Most recently, I launched a new practice called FxMed Mental Health, which brings together functional medicine, nutrition, psychiatry, mental health, psychedelics, and so much more.
Q: Your work often challenges conventional mental health models. How do you see the role of biology in mental health today?
DW: The dominant biological model in mental health has been heavily shaped by pharmaceutical research, primarily the idea that neurochemical imbalances can be corrected with medication. While medications can be helpful, in my view, that framework is incomplete.
There’s growing recognition that many biological systems influence mental health: the gut microbiome, immune function, inflammation, nutrient status, even metabolic states like ketosis. Functional medicine tries to explore these root causes more deeply through the use of tools like stool testing, genetic analysis, and nutrient assessments to personalize care.
What’s frustrating is that these approaches are often labeled “alternative,” even though they actually do aim to address underlying biology. Meanwhile, many people aren’t getting better with standard treatments, in part because we treat conditions like depression as if they’re uniform. In reality, there are many different subtypes, each of which requires different interventions.
At the same time, there are real equity issues with this space. Functional medicine tools can be expensive and aren’t widely covered by insurance, which risks widening health disparities. I see this as a major challenge that must be solved.
Throughout his career, David has worked to bridge the cultural divide between traditional eating disorder and addiction recovery nutritional approaches and science-based, functional models.
Q: You’ve done extensive work on food addiction and ultra-processed foods. How do you see this fitting into the broader mental health landscape?
DW: We’re in the middle of a nutritional crisis that’s deeply tied to chronic disease and mental health. Ultra-processed foods are engineered to be highly rewarding and, in many cases, addictive. Even those with education and adequate access can struggle with them, especially given the high stress lifestyles of the modern moment.
I’ve been particularly focused on what I call “ultra-processed food use disorder.” Unlike substances, we can’t abstain from food entirely, so the goal becomes harm reduction—reducing exposure and improving dietary patterns without creating additional psychological harm through patterns like rigid dieting and restriction.
There’s also a broader systems issue. Food environments are shaped by powerful industries that exploit neurobiological vulnerabilities, especially in marginalized communities. This isn’t just about personal responsibility, it’s about policy, regulation, and accountability.
At the same time, labeling something as addiction can be tricky because of stigma. But interestingly, some research suggests that understanding overeating through a neurobiological lens can actually reduce shame by shifting blame away from moral failure.
Q: You’ve worked across both eating disorder treatment and addiction recovery. What tensions do you see between these fields?
DW: There’s a real cultural divide. On one side, you have traditional eating disorder approaches like “all foods fit.” On the other, there are more neuroscience-based addiction models that emphasize the impact of highly processed foods from a psychological and biological perspective.
Patients often feel caught in the middle, receiving conflicting advice from different providers. That creates confusion and noise. A big part of my work has been helping people navigate these competing frameworks. I encourage metacognition rather than pushing a single philosophy.
Different people need different approaches. Some benefit from more structure, others from flexibility. Increasingly, I’ve also come to see the importance of spiritual recovery, which involves addressing the deeper human need for connection and meaning that often underlies both addiction and disordered eating.
I recently wrote a paper that unpacks this and proposes a unified theory.
Q: You’ve mentioned spirituality and plant medicine as part of your work. How did that enter the picture?
DW: It started with my patients. About six or seven years ago, I worked with someone who had struggled with bulimia for over a decade. We made progress, but some core issues, like body image, persisted. She later went on a plant medicine retreat in South America, and when she came back, it was evident that something profound had shifted. She felt more at ease in her body and more connected to natural foods and her environment.
That experience changed my perspective. I began to see how these experiences could help people reconnect with themselves, with nature, and with something larger than themselves. I see spiritual recovery as a component of finding balance that is just as important as addressing brain chemistry, psychosocial factors, isolation, loneliness, etc. The root of so many challenges is a yearning for connection, and in my view, this can be an intergenerational struggle. In my experience, many mental health challenges can be understood as forms of disconnection, whether that disconnection is from community, the body, or meaning itself. Psychedelic experiences, when used responsibly, seem to accelerate reconnection. Plant medicine also represents a disruption to the pharma-controlled system, providing people with alternatives that have the potential to really revolutionize mental health care.
At the same time, this is a complex and evolving space, especially for people with addiction histories. There’s a lot we still need to learn, and I’m actively engaged in those conversations.
Q: You’ve also studied the influence of industry on health. How does that shape your perspective?
DW: Industries like food and pharmaceuticals have enormous influence over public discourse and research. They’re highly sophisticated in how they shape narratives and even polarize conversations.
Understanding these dynamics is important if we want to create meaningful change. Whether it’s the opioid crisis or the rise of ultra-processed foods, we see patterns where harm becomes normalized as part of doing business. I see that nutrition has been an unspoken tool of oppression in society, such as institutional nutrition in carceral settings.
At the same time, I’m seeing growing resistance. More practitioners and researchers are willing to challenge the status quo and explore new models of care.
Q: What does the future of your work—and the field more broadly—look like?
DW: I see a more integrated, collaborative model of care. Nutrition, psychiatry, psychology, and functional medicine all working together. There’s also a huge role for technology—especially AI—in helping us synthesize complex data from multiple systems and identify patterns we might otherwise miss.
I’ve developed a mobile app that uses nutritional and functional health data to support mental health. The goal is to move beyond siloed thinking and toward a truly biopsychosocial model that incorporates and synthesizes functional labs, behavioral patterns, and nutritional inputs.
Overall, I’m focused on bridging modern technology with more holistic approaches to care, and I’m encouraged by a growing community of practitioners who are willing to question the status quo and move the field forward together.
Q: As you reflect on your journey to arrive where you are today, would you say that there was a personal turning point that shifted how you view mental health?
DW: Yes, absolutely, my own lived experience with addiction in my early twenties. That period was pretty gnarly, and it absolutely impacted everything that followed. I’ve been in recovery ever since, and that identity informed the first decade of my career. When I launched Nutrition in Recovery, I was committed to bringing nutritional therapy to people in the system—I had the knowledge and the lived experience that really appealed to people.
Over time, though, I realized I needed to expand beyond that lens to reach a broader and more diverse spectrum of people, which is what led me toward a more holistic focus on mental health, functional medicine, and systems-level change. Despite the complexities of this moment, I am hopeful about where we stand today. Change is happening, and it’s an honor to play a role in helping people heal.
This interview is part of the Nova Institute for Health’s Insight Collaborative for Mental Well-Being project. The Insight Collaborative is supported by a generous seed grant from the Mental Insight Foundation.
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