The Gravity Doctors

Dr Brennan Spiegel (physician, gastroenterologist, and author of Pull) and Dr Lachlan Kent (cognitive scientist and founder of Mental Gravity) explore serotonin as a gravity-management molecule, reframing it not simply as a “happiness chemical,” but as a fundamental biological system that allows life to stand up, move fluids, regulate balance, and remain psychologically buoyant in a gravitational field.Together, Brennan and Lachlan unpack new research on serotonin’s role across the gut, cardiovascular system, lymphatics, vestibular system, reproduction, and mood—showing how 95% of serotonin is produced in the gut, in symbiosis with the microbiome. They trace serotonin’s evolutionary origins from ocean life to land, altitude, and even space, and discuss practical implications for diet, exercise, sunlight, microbiome care, and mental health.1. What Is Serotonin?A whole-body gravity resilience molecule, not just a brainneurotransmitter Exists in two largely separate compartments: brain and gutCentral to movement, circulation, balance, mood, and vitalityEvolutionarily conserved across plants, animals, and humansSerotonin as a Gravity-Management SystemGut & DigestionMotility against gravity in any body orientationPumps & TubesBlood pressure regulation, cardiac contractility, lymphatic returnBalance& OrientationVestibular function; dizziness during SSRI withdrawalReproductionRetrograde uterine contractions that move sperm upward against gravityMood &EnergyMental elevation, vitality, resilience, and time perceptionThe Microbiome–Serotonin AllianceTrillionsof microbes are required to trigger serotonin productionThe gut as a “dark, sulfurous, hydrothermal” evolutionary nicheA symbiotic bargain: microbes get mobility; humans get serotoninChanges in altitude, microgravity, and spaceflight rapidly alter serotoninbiologySTACK TEN: The Anti-Gravity Diet (introduced)A practical framework from Pull for supporting serotonin production via tryptophan-rich foods.Core principles:Tryptophan as substrateMicrobiome diversityDietary balance rather than supplementation aloneTherapeutic & Self-Care ImplicationsDietary modification (tryptophan-rich foods, microbiome-supportive diets)Exercise and movementSunlight and time outdoorsWorking with dietitians for GI and mood conditions (e.g., low-FODMAP when indicated)Understanding limits and side effects of SSRIsNaturally supporting serotonin across body and mindMetaphor & MeaningThe gutmicrobiome as the “spice factory” of human biologySerotonin as the true “spice of life”—powerful, regulating, and double-edgedGravity as the organizing principle linking biology, psychology, and medicineTimecodes00:00 —Welcome & why serotonin matters01:10 — Serotonin beyond the “happiness chemical”02:20 — Gut vs brain serotonin compartments03:20 — Pumps, tubes & whole-body effects04:25 — Lymphatics, reproduction & balance06:20 — Evolutionary origins & gravitation08:10 — Microbiome symbiosis metaphor10:15 — Altitude, spaceflight & serotonin disruption11:30 — STACK TEN diet introduced12:45 — Diet, microbiome & mood disorders13:50 — Dune, spice & serotonin metaphor15:45 — SSRIs: benefits, limits & side effects17:00 — Natural serotonin support & integration17:45 — Closing reflections & next stepsResourcesThe Gravity Doctors website: https://thegravitydoctors.comDr Brennan Spiegel: https://brennanspiegelmd.comDr Lachlan Kent: https://lachlankent.auBook — Pull: How Gravity Shapes Your Body, Steadies the Mind, and Guides Our Health 

Dr Brennan Spiegel (physician, gastroenterologist, and author of Pull) and Dr Lachlan Kent (cognitive scientist and founder of Mental Gravity) explore how diet, microbiome diversity, and serotonin production shape your capacity to stand up to gravity—physically and mentally.They introduce the Anti-Gravity Diet and Brennan’s STACK TEN framework, a simple, evidence-informed way to support the gut’s serotonin “factories” and improve whole-body gravity resilience. Along the way, they unpack how food, fibre, omega-3s, polyphenols, vagus-nerve activation, and mindful rest all participate in the body–mind system that keeps us upright and energised.Together, Brennan and Lachlan discuss babies as “gravity novices,” leaky gut, the gut–brain axis, evolutionary embodiment, time dilation in depression, and why serotonin—serum tone—is essential for managing the constant downward pull of Earth’s gravity.A holistic framework for supporting natural serotonin production—the body’s anti-gravity molecule.Grounded in gastrointestinal physiology, microbiome science, and biogravitational medicine. Not a restrictive diet — a practical, everyday toolkit for gravity resilience.A memory device for foods that supply the raw material (tryptophan) for serotonin production:SalmonTurkeyAvocadoChickpeasKidney beansTofu/TempehEggsNutsPaired with:Fibre → feeds microbes that create short-chain fatty acidsOmega-3s → shift the microbiome toward serotonin-supporting speciesPolyphenols → found in berries, cocoa, turmeric, and green tea00:00 — Welcome & overview of the Anti-Gravity Diet01:20 — Serotonin as the body’s anti-gravity molecule04:20 — Microbiome diversity & the gut barrier06:30 — Babies, serotonin & early gravity resilience09:40 — Tryptophan, fibre & short-chain fatty acids11:00 — Leaky gut, inflammation & decoherence13:00 — Food–mood science & depression16:40 — What to eat: introducing STACK TEN17:00 — The ten tryptophan-rich foods18:50 — Polyphenols, omega-3s & microbiome tuning19:50 — Beyond diet: exercise, nature, sunlight21:20 — Balancing sympathetic vs parasympathetic tone23:00 — Vagus-nerve stimulation & rest-and-digest24:30 — Gravity as the integrator across biological levels26:00 — Life as a system for managing gravity27:20 — Closing reflections & future topicsThe Gravity Doctors website: ⁠https://thegravitydoctors.com⁠Gravitype Quiz: virtualmedicine.org/pullDr Brennan Spiegel: brennanspiegelmd.comDr Lachlan Kent: lachlankent.auBook — Pull: How Gravity Shapes Your Body, Steadies the Mind, and Guides Our Health

In this episode, Dr Brennan Spiegel (physician, gastroenterologist, and author of Pull) and Dr Lachlan Kent (cognitive scientist and founder of Mental Gravity) dive deep into gravity resilience and introduce listeners to the new Gravitype Quiz—a wellness tool that blends biomechanics, neuroscience, and psychology to help people understand their personal relationship with gravity.Together, Brennan and Lachlan take the quiz live on the show and compare results, unpacking the three pillars of biogravitational health: gravity fortitude, gravity sensing, and mental gravity. Along the way, they explore back pain, dizziness, cold exposure, resilience, interoception, emotional balance, and how experiences like roller coasters or elevators reveal something about your gravitational tendencies.You can try the full interactive quiz here:brennanspiegelmd.comvirtualmedicine.org/pullthegravitydoctors.com1. What Is a Gravitype?A personalised profile of gravity resilienceBased on the framework in Pull and grounded in emerging concepts in biogravitational medicineNot a diagnostic tool — currently evidence-informed and intended for education/wellnessGravity FortitudeMuscles, bones, pumps, and tubesCardiovascular and postural strengthBack pain, leg swelling, stair climbing, grip strengthGravity SensingInner ear, proprioception, vestibular functionBalance tests (like one-leg standing)Cold sensitivity, interoception, dizziness/vertigoMental GravityWeighted-down vs upliftedStress tolerance, emotional recovery, “flow” statesDual-continuum model of mental healthGrip strength as a predictor of longevityBMI and physical load on the spineOrthostatic light-headedness and blood pressure regulationInner-ear disorders (e.g., BPPV) and sensory hypersensitivityThe anterior insula as the “gravity conductor” of the body–mind symphonyThey answer questions on:Opening a jarClimbing stairsBack painLight-headednessBalanceCold toleranceEmotional reactivity and resilienceRoller coaster sensitivityPositive emotional absorption (flow)Each reflects personally on past injuries, thyroid health, yoga, meditation, diet, travel, and evolving gravitational resilience across their lives.Durable fortitudeNormosensitive sensingLifted mental gravityNotes how training (cold exposure, yoga, flying) reshaped Lachlan's sensitivity over time.Reflections on vertigo, cold intolerance, and emotional uplift as part of Brennan's profile.Both discuss how gravitypes can change with training, awareness, and targeted practices.Examples include:Down-regulating sensory overload (slow nasal breathing, longer exhales, box breathing)Strengthening the gravity fortitude system (movement, posture, reducing sitting time)Noticing “watch-outs” such as back pain, dizziness, or emotional ruminationLinks included in the show notes.00:00 — Welcome, origins of the gravitype01:30 — Gravity resilience basics03:00 — Gravity fortitude (muscles, tubes, pumps)06:45 — Mental gravity explained08:00 — Starting the quiz09:00 — Grip strength & longevity11:00 — Stair climbing & cardiovascular load12:00 — Back pain & evolution15:00 — Orthostatic dizziness & fainting18:00 — BMI, weight, and gravitational load20:00 — Leg swelling, pumps & tubes23:30 — Gravity sensing & vertigo25:00 — Balance tests (one-leg stance)26:30 — Cold sensitivity & nervous-system tuning29:30 — Interoception & the anterior insula33:00 — Stress, heaviness & mental gravity36:00 — Roller coasters, turbulence & fear responses38:00 — Emotional resilience and bouncing back41:00 — Flow states and uplift43:00 — Revealing their gravitypes46:30 — What their results mean48:00 — Final reflections & where to take the quizThe Gravity Doctors website: https://thegravitydoctors.comGravitype Quiz: available on BrennanSpeigelMD.com & virtualmedicine.orgDr Brennan Spiegel: brennanspiegelmd.comDr Lachlan Kent: lachlankent.auBook — Pull: How Gravity Shapes Your Body, Steadies the Mind, and Guides Our Health

Dr. Brennan Spiegel (Cedars-Sinai) and Dr. Lachlan Kent explore how gravity shapes not only our bodies but our minds. Through the lens of Cathy Freeman’s gold-medal run, they discuss mental gravity — the feeling of emotional “weight” and lightness that defines human experience.From Einstein’s relativity to embodied cognition and Cedars-Sinai’s virtual-reality therapy, they connect physics, psychology, and physiology to show how alignment with gravity may be the key to wellbeing. Topics include depression as a “mental gravity well,” glucose and perception, VR and levity, and how mindfulness, diet, and physical balance can help us stay buoyant in heavy times.Key themes:Mental Gravity: The experience of emotional and cognitive “weight,” shaped by our alignment with the physical world’s gravitational pull.Embodied Cognition: How bodily states and forces (like gravity, glucose, or posture) shape perception and thought.Gravity Intolerance: A unifying framework for disorders where physical and mental balance are disrupted.Mind over Matter: Using imagery, mindfulness, and movement to generate upward momentum and emotional lightness.Timecodes:00:00 – 01:30 | Welcome to The Gravity DoctorsIntroducing Brennan and Lachlan; overview of physical and mental gravity.01:30 – 03:50 | The Cathy Freeman StoryHow Cathy transcended the “weight of expectation” to run with joy and lightness — an example of mental gravity at its best.03:50 – 06:00 | The Weight of EmotionExploring why positive emotions feel light and negative emotions feel heavy — from embodied metaphors to physical postures of depression.06:00 – 08:10 | Embodied Cognition and Glucose StudiesBrennan cites research showing blood-glucose levels alter perception of hill steepness — a literal bridge between physiology and perception.08:10 – 11:00 | The Birth of the Theory of Mental GravityLachlan recalls his “aha” moment linking Einstein’s general relativity lecture on black holes to psychological depression — both described using the same language of heaviness, collapse, and isolation.11:00 – 12:40 | Gravity Wells, Black Holes, and RecoveryComparing mental “gravity wells” to depression — but unlike black holes, people can pull themselves out.12:40 – 16:20 | Champagne, Joy, and the Physics of EmotionWhy celebration rituals mirror gravitational metaphors — bubbles rising, buoyancy, and the inevitable “come-down.”16:20 – 19:30 | Virtual Reality as a Gravity-Hacking ToolCedars-Sinai research: VR experiences that simulate floating or flying reduce pain, anxiety, and inflammation — measurable physiological effects of simulated levity.19:30 – 22:00 | Mindfulness and Mental ImageryUsing mental imagery and meditation to reshape the brain-body landscape and foster feelings of lightness and alignment.22:00 – 25:50 | The Continuum of Mind and BodyWhy mind and body aren’t separate but part of one continuous system — like a cross-country landscape shifting seamlessly from desert to sea.25:50 – 28:30 | Gravity Intolerance and Health ResilienceReframing conditions like IBS, POTS, and anxiety as variations of gravity intolerance; maintaining physical and mental balance as the essence of wellbeing.28:30 – 30:00 | Everyday Applications & Closing ReflectionsFrom mindfulness to serotonin-rich diets and time in nature — practical tools to stay buoyant.Final reflections on finding balance between empowerment and medical treatment.Want to discover your 'Gravitype'? Visit The Gravity Doctors website:https://thegravitydoctors.com/Order Brennan's book "Pull" to learn more about how gravity shapes your health in both body and mind via his personal ⁠⁠personal website⁠⁠: https://www.brennanspiegelmd.com/pullVisit ⁠⁠Lachlan's website ⁠⁠to learn more about his work in mental gravity: https://lachlankent.au/Music by ⁠ALLIRA⁠ and Visceral Sound - https://www.youtube.com/@ALLIRAmusicRecording at ⁠JTB Studio⁠ by David Iskandaryan.

In this uplifting and deeply human episode of The Gravity Doctors, Dr. Brennan Spiegel (Cedars-Sinai gastroenterologist and author of PULL) and Dr. Lachlan Kent (cognitive scientist and theorist of Mental Gravity) sit down with Harmon Clarke, a patient-turned-researcher whose remarkable recovery story illuminates the future of biogravitational medicine.From septic shock and 200 days in hospital to yoga teacher, breathwork practitioner, and health researcher, Harmon’s journey embodies resilience, creativity, and the healing power of re-engaging with gravity. Together, they explore how movement, inversions, virtual reality, and breathwork can transform pain and depression into buoyancy and balance — culminating in a spontaneous “Gravity Rap” that captures the spirit of the show.Core ThemesGravity as a unifying metaphor for physical and mental healthMovement and inversion therapy for resilience and recoveryVirtual reality and embodied cognitionTensegrity, balance, and the biomechanics of wellbeingPatient empowerment and the hero’s journey in healingBiogravitational medicine as a synthesis of East–West paradigms00:00 – Welcome and Introductions01:00 – Facing the Grave03:00 – Virtual Reality and the Mind–Body Connection06:00 – Yoga, Breathwork, and Natural Recovery08:00 – The Science of Inversion and Tensegrity14:00 – Hospitals and Gravity Intolerance18:00 – Depression as a Gravitational Condition24:00 – Cathy Freeman and Gravitational Flow25:45 – East Meets West30:00 – Rebalancing Medicine33:00 – The Simple Tools of Healing35:00 – Designing the Future of Biogravitational Medicine38:00 – Generational Health and Modern Comfort41:00 – The Gravity Rap Finale Order Brennan's book "Pull" to learn more about how gravity shapes your health in both body and mind via his personal ⁠⁠personal website⁠⁠.Visit ⁠⁠Lachlan's website ⁠⁠to learn more about his work in mental gravity. Music by ⁠ALLIRA⁠ and Visceral SoundRecording at JTB Studio by David Iskandaryan. Editing by Dr Karisma Suchak.

Biogravitational Medicine is a holistic approach to maintaining health in both body and mind. It's like a toolkit where you can find what works for you and your particular situation. Here are our top ten that work for most people most of the time. (As always, consult a doctor for personalised medical advice before attempting anything that might pose a risk to your physical or mental health, or for treatment of acute or chronic conditions. The information here is for educational and information purposes only.) Order Brennan's book "Pull" to learn more about how gravity shapes your health in both body and mind via his personal ⁠personal website⁠.Visit ⁠Lachlan's website ⁠to learn more about his work in mental gravity.Music by ALLIRA and Visceral SoundThis episode was recorded at ⁠Myst Music⁠.Audio engineering by Jeremy Roberts.Audio and video editing by Dr Karisma Suchak.

Dr Spiegel has written a book about gravitational health called 'Pull' on the wide ranging themes underpinning this podcast - gut health, mental gravity, serotonin, the inner ear, the body's pumps and tubes, the gravitostat, and many more. The hosts take a tour through the world of biogravitational medicine by telling the story of what inspired the book, where the science is heading, and how people can apply the principles in their daily lives.Order Brennan's book "Pull" to learn more about how gravity shapes your health in both body and mind via his personal personal website.Visit Lachlan's website to learn more about his work in mental gravity.Music by ALLIRA and Visceral Sound.This episode was recorded at Myst Music.Thanks to Jeremy Roberts for audio engineering and Dr Karisma Suchak for editing.

You know the feeling you get in your belly when falling on a rollercoaster? Ever wondered why we get similar gut feelings when we're "falling" in love?  In this episode, Brennan (a gastroenterologist) and Lachlan (a cognitive scientist) talk about how gravity shapes gastrointestinal function and what relation gut feelings have to physical and mental health. They discuss Brennan's viral scientific paper, "Gravity and the Gut: A Hypothesis of Irritable Bowel Syndrome" and Lachlan's breakthrough theory of the mind called "Mental Gravity", and the connections between their shared ideas. Conditions like IBS often lead to anxiety and depression, which are the mental equivalent of "falling" and having "fallen", and so they draw a connection between gut health, gut feelings, and mental health. Strap yourself in for a rollercoaster ride through the topsy-turvy world of gut feelings in both body and mind.Order Brennan's book "Pull" to learn more about how gravity shapes your health in both body and mind via his personal personal website.Visit Lachlan's website to learn more about his work in mental gravity.Music by ALLIRA and Visceral Sound.This episode was recorded at ⁠Myst Music⁠.Thanks to Jeremy Roberts for audio engineering.