Introduction: a psychiatrist on training
John Ratey is clinical professor of psychiatry at Harvard Medical School and a specialist in ADHD and the neurobiology of physical activity. His book "Spark: The Revolutionary New Science of Exercise and the Brain" (Little, Brown, 2008) was the first popular work to systematically synthesise the neurobiological literature on the effects of exercise on the brain.
In the 17 years since publication the book's main paradigm — BDNF as the key mechanism of exercise on the brain — has withstood serious scientific scrutiny and remained fundamentally correct. That is unusual for popular science. The book matters to an endocrinologist because metabolic health and neuropsychiatry are parts of one system, and physical activity is the single most powerful intervention affecting both.
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#first_exercise_is_medicine
The central thesis: physical activity is not "lifestyle support" but a specific biological intervention with effects comparable to pharmacotherapy for several neuropsychiatric conditions.
Depression: meta-analysis Schuch FB et al., *J Psychiatr Res* 2016 (PMID 27253131) — exercise produces an effect on mild-to-moderate depression comparable to CBT and SSRIs. RCT Blumenthal JA et al., *Arch Intern Med* 1999 (PMID 10547175) — 16 weeks of aerobic exercise in patients with major depressive disorder produced clinical efficacy comparable to sertraline; at 10 months the relapse rate in the exercise group was lower.
Anxiety: meta-analysis Aylett E et al., *BMC Health Serv Res* 2018 (PMID 30068345) — moderate-intensity exercise significantly reduces symptoms of generalised anxiety disorder; the effect is sustained at 12+ weeks.
ADHD: RCT Pontifex MB et al., *J Pediatr* 2013 (PMID 23159160) — 20 minutes of aerobic exercise in children with ADHD improves inhibition and goal-directed behaviour for the next 60–90 minutes; the effect is comparable to a single stimulant dose.
Cognitive function in older adults: meta-analysis Northey JM et al., *Br J Sports Med* 2018 (PMID 28438770) — aerobic and resistance exercise in older adults improves executive function, episodic memory and processing speed.
Neuroprotection: prospective cohorts show that regular physical activity is associated with a 30–40% reduction in the risk of Alzheimer's disease and vascular dementia (Larson EB et al., *Ann Intern Med* 2006, PMID 16418406). This is the strongest effect of any modifiable risk factor.
Clinical implication: in my practice, when assessing a patient with metabolic, neuropsychiatric or endocrine disturbance, physical activity is a mandatory part of the treatment plan, not "additional advice". I ask concrete questions: how many hours per week, what intensity, what types, what regularity. If activity is absent or irregular, this is a first-line target of intervention, sometimes a higher priority than pharmacotherapy.
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#second_bdnf_miracle_gro
The second central concept is BDNF (brain-derived neurotrophic factor) as "Miracle-Gro for the brain". Ratey popularised this metaphor and it has stuck.
BDNF is a neurotrophin that: - Stimulates neurogenesis in the dentate gyrus of the hippocampus (one of the two regions in the adult human brain with continuing neurogenesis) - Supports synaptic plasticity — the basis of learning and long-term memory - Protects neurons from damage by oxidative stress, excitotoxicity and amyloid toxicity - Regulates mood, appetite and glucose metabolism (BDNF also has peripheral receptors)
Physical activity is the most potent known inducer of BDNF. One hour of moderate-intensity aerobic exercise raises blood BDNF by 30–80% in healthy adults (Knaepen K et al., *Sports Med* 2010, PMID 20836577). Regular training (3–5 times per week for 8+ weeks) raises baseline BDNF and increases reactivity.
In parallel other neurotrophic factors rise: IGF-1 (insulin-like growth factor 1) — neurogenesis, neuroprotection; VEGF (vascular endothelial growth factor) — angiogenesis, cerebral perfusion; FGF-2 (fibroblast growth factor 2) — cellular proliferation; irisin — a recently discovered myokine with direct effects on neurogenesis.
This is not "supporting good wellbeing". It is direct biochemical reprogramming of the brain via physical activity.
An additional mechanism is reduction of neuroinflammation. Exercise reduces systemic pro-inflammatory markers (CRP, IL-6, TNF-α) and raises anti-inflammatory ones (IL-10). Neuroinflammation is a common mechanism in depression, neurodegeneration and cognitive impairment.
Clinical implication: when working with a patient for neuropsychiatric or metabolic indications I do not prescribe BDNF in tablets — it is not orally bioavailable and does not cross the blood-brain barrier when injected. The only reliable way to raise BDNF in the brain is physical activity plus other stimuli (cognitively complex tasks, social interaction, novelty, brief fasting).
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#third_naperville_cardio_before_learning
The third part of the book is a practical illustration. Ratey documents Naperville Central High School (Illinois) — the Zero-Hour PE programme. Pupils take intensive cardio (running, stationary bike, swimming) before academic classes start.
Results: over eight years of the programme the school went from ordinary to #1 in the international TIMSS test in mathematics and science among eighth-graders. Obesity among students fell from 30% (national norm) to 3%. Disciplinary incidents fell by 67%.
Naperville is a case study, not an RCT, so causation is not strictly established. But parallel laboratory data support the interpretation: 20 minutes of aerobic exercise immediately before a cognitive task improves executive function, attention and processing speed (Tomporowski PD et al., *Educ Psychol Rev* 2008).
The biological mechanism: acute increase in cerebral blood flow + rise in BDNF + catecholaminergic activation + reduction in anxiety. These effects persist for 60–120 minutes after exercise — a window for learning.
Clinical implication: for patients with cognitive complaints (brain fog, concentration problems, fatigue during the workday) I recommend cardio before an intellectually loaded day, not in the evening. 20–30 minutes of moderate aerobic activity in the morning gives a cognitive bump for the first 2–3 hours of work — particularly effective for intellectual professions.
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#critique
Ratey's book is foundational and scientifically grounded but has limitations:
Nonetheless the basic neurobiological model — BDNF and related growth factors as mediators of exercise effects on the brain — remains fundamentally sound and corroborated over the past 17 years.
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#summary
What is strong: systematic description of the neurobiological effects of exercise; BDNF and related growth factors as mechanism; the parallels between exercise and pharmacotherapy for a range of neuropsychiatric conditions; a concrete illustration (Naperville).
What requires caution: some mechanisms are outdated; "exercise for everything" is in places overstated; not all forms of activity are equivalent.
What is critically important: the book is for understanding the biological significance of regular physical activity and its effect on the brain. It is not a textbook for the treatment of clinical depression or neurodegeneration — the standards remain in the relevant specialties. But as a mandatory component of preventive, therapeutic and rehabilitative strategy, exercise belongs in every patient's plan.
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#practical_minimum
Applied to daily clinical practice:
Minimum neuroprotective dose: - Moderate-intensity aerobic exercise (60–70% of maximum heart rate) 150 minutes per week — the minimum for a basic neurobiological effect - Resistance training twice a week — for maintenance of muscle mass, IGF-1 and insulin sensitivity - High-intensity intervals (HIIT) 1–2 times a week — for the mitochondrial and BDNF effect
Timing: morning training gives the greatest cognitive effect during the day; evening training can disturb sleep in some patients (individual). For depressed patients, morning training in daylight combines the exercise effect with circadian regulation.
For neuropsychiatric indications: exercise as a first or second line for mild-to-moderate depression, ADHD and anxiety; as a mandatory adjunct to pharmacotherapy for moderate-to-severe conditions; as a neuroprotective strategy in APOE4 carriers or those with a family history of neurodegeneration.
Barriers to practice: depression and chronic fatigue reduce motivation to exercise — a paradox. Start with very small doses (10 minutes of a morning walk) and increase gradually. Social context (group classes, walks with loved ones, pets) significantly improves adherence.
Laboratory for response assessment: blood BDNF is not yet a routine marker but is used in research. Indirect markers of exercise effect: hsCRP (falls), HOMA-IR (improves), HDL (rises), HbA1c (falls), HRV (improves).
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#about_the_reviewer
Dr. Vladimir Pereligyn — endocrinologist. Functional medicine with a focus on preventive strategies: metabolic health, thyroid function, hormonal balance, and individualised risk profiling based on extended laboratory diagnostics. Consultations in person and online: [universum.earth/consultation](/consultation). App Store: Teremok (type 2 diabetes, remission).
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Source
▸ Ratey JJ, Hagerman E. *Spark: The Revolutionary New Science of Exercise and the Brain*. Little, Brown and Company, New York, 2008. ISBN 978-0316113502. 304 pages.
Further reading on the topics of this review: ▸ Schuch FB, Vancampfort D, Richards J, et al. Exercise as a treatment for depression: A meta-analysis adjusting for publication bias. *J Psychiatr Res* 2016;77:42-51. PMID 27253131 ▸ Knaepen K, Goekint M, Heyman EM, Meeusen R. Neuroplasticity - exercise-induced response of peripheral brain-derived neurotrophic factor: a systematic review of experimental studies in human subjects. *Sports Med* 2010;40(9):765-801. PMID 20836577 ▸ Northey JM, Cherbuin N, Pumpa KL, et al. Exercise interventions for cognitive function in adults older than 50: a systematic review with meta-analysis. *Br J Sports Med* 2018;52(3):154-160. PMID 28438770 ▸ Larson EB, Wang L, Bowen JD, et al. Exercise is associated with reduced risk for incident dementia among persons 65 years of age and older. *Ann Intern Med* 2006;144(2):73-81. PMID 16418406 ▸ Pontifex MB, Saliba BJ, Raine LB, Picchietti DL, Hillman CH. Exercise improves behavioral, neurocognitive, and scholastic performance in children with attention-deficit/hyperactivity disorder. *J Pediatr* 2013;162(3):543-51. PMID 23159160
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*This review reflects the author's clinical interpretation and does not replace consultation with a physician. Before changing therapy, diagnostic protocols or lifestyle, discuss the plan with your treating specialist.*
