Dr Casey Means and Good Energy: The Metabolic Root of Chronic Disease
Dr Casey Means is a Stanford-trained surgeon who left medicine to argue that the system she trained in is treating symptoms rather than causes. Her 2024 book Good Energy, co-written with her brother Calley Means, makes a specific and data-grounded case: the epidemic of chronic disease in the US — obesity, type 2 diabetes, heart disease, depression, infertility — shares a common root in metabolic dysfunction, and that dysfunction is largely driven by choices and environments that current healthcare has neither the incentive nor the framework to address. The book is not a self-help guide in the conventional sense. It is a structural critique of American healthcare delivered through the lens of metabolic science, with practical protocols attached.
- → Means argues that over 93% of American adults have suboptimal metabolic health — and that this underlies most chronic disease, including conditions not typically framed as metabolic
- → Mitochondrial function — the body’s capacity to convert nutrients into usable energy (ATP) — is the central mechanism linking lifestyle to disease risk
- → The book identifies six biomarkers — fasting glucose, triglycerides, HDL cholesterol, blood pressure, waist circumference, and HbA1c — as the practical scorecard for metabolic health
- → Means co-founded Levels, a continuous glucose monitoring platform, based on the thesis that real-time metabolic data changes behaviour in ways that retrospective advice cannot
- → Her practical interventions are evidence-grounded and non-extreme: dietary quality over restriction, consistent moderate exercise, sleep optimisation, and time-restricted eating
The Central Argument: Metabolic Dysfunction as Root Cause
The book’s foundational claim is that the major chronic diseases of the 21st century — which now account for 90% of US healthcare spending — are not separate conditions requiring separate treatments but expressions of the same underlying dysfunction: cells that cannot efficiently produce and use energy. When mitochondria — the organelles responsible for converting nutrients into ATP — are impaired by chronic glucose dysregulation, inflammation, oxidative stress, and nutrient deficiency, the downstream effects manifest across every organ system.
This framing is not new in metabolic medicine, but Means presents it accessibly and with specific mechanistic explanations. She traces how insulin resistance — the failure of cells to respond appropriately to insulin signalling — precedes and contributes to conditions as apparently unrelated as PCOS, Alzheimer’s disease, depression, and certain cancers. The common thread is impaired cellular energy metabolism, and the common driver is the modern environment’s combination of ultra-processed food, sedentary behaviour, sleep disruption, chronic stress, and environmental toxin exposure.
The premise of Good Energy is that feeling vibrant is not the absence of diagnosed disease. It is cells producing energy efficiently, hormones signalling correctly, and inflammation held in check — none of which show up in a standard annual physical until they have already deteriorated significantly.
The Six Metabolic Biomarkers
Means organises her diagnostic framework around six measurable markers that collectively indicate metabolic health. These are available through standard blood panels and do not require specialised testing:
Fasting glucose — the baseline blood sugar level after an overnight fast. Means argues that optimal is below 85 mg/dL; the clinical “normal” range extends to 99 mg/dL, which she considers meaninglessly wide given the continuous relationship between glucose and disease risk.
Triglycerides — blood fats that rise with dietary carbohydrate intake and insulin resistance. Optimal below 100 mg/dL; most labs flag anything below 150 as normal.
HDL cholesterol — the lipoprotein associated with reverse cholesterol transport and cardiovascular protection. Target above 60 mg/dL in men, above 70 mg/dL in women.
Blood pressure — systolic below 120 mmHg, diastolic below 80 mmHg. Hypertension is both a symptom and accelerator of metabolic disease.
Waist circumference — a proxy for visceral fat (fat stored around organs), which is metabolically active and inflammatory in ways subcutaneous fat is not. Below 94 cm in men, below 80 cm in women.
HbA1c — glycated haemoglobin, reflecting average blood glucose over the past 90 days. Optimal below 5.4%; anything above 5.7% is classified as pre-diabetic.
Means co-founded Levels, which integrates CGM data with dietary and activity tracking to show how individual foods, exercise, sleep, and stress affect blood glucose in real time. The core insight from CGM research is that glucose response is highly individual — the same meal can spike one person’s glucose sharply while barely affecting another’s, due to differences in gut microbiome, insulin sensitivity, and genetics. This variability makes population-level dietary advice imprecise; CGM enables personalisation.
The Practical Protocols
The book’s second half translates the mechanistic case into actionable interventions. Means is careful to position these as evidence-based rather than extreme — the protocols are demanding in their consistency but not in their complexity.
Dietary quality over macronutrient restriction. Means does not advocate a specific diet — keto, low-fat, vegan — but argues consistently for eliminating ultra-processed foods, refined seed oils, and added sugars while prioritising whole foods with high fibre density. The reasoning is mechanistic: ultra-processed foods are engineered to override satiety signals, disrupt the gut microbiome, and drive postprandial glucose spikes. The fibre target she cites — 50+ grams daily — is well above the average American intake of 15 grams.
Time-restricted eating. Concentrating food intake within a 10-hour window (e.g. 8am–6pm) allows for a daily metabolic rest period that improves insulin sensitivity, supports circadian rhythm alignment, and reduces the total insulin secretion burden. The evidence base here is substantial and growing, though optimal window duration remains debated.
Post-meal movement. A 10-minute walk after meals significantly blunts the postprandial glucose response by driving glucose into skeletal muscle through a non-insulin-dependent pathway. This is one of the most reproducible and accessible metabolic interventions in the literature — low effort, immediate measurable effect.
Sleep optimisation. Means frames poor sleep not as a productivity issue but as a metabolic one: a single night of sleep deprivation produces insulin resistance equivalent to six months of poor diet. Target is 7–9 hours with consistent sleep and wake times, dark and cool environment, and screen elimination in the hour before bed.
The Systemic Critique
Beyond the personal health framework, Good Energy makes a structural argument that has attracted both attention and controversy. Means and her brother argue that the US healthcare system — specifically the pharmaceutical industry’s influence on medical education, research funding, and clinical practice — has a financial incentive to treat chronic disease rather than prevent it, and that the food industry’s influence on dietary guidelines has systematically obscured the relationship between ultra-processed food and metabolic dysfunction.
This critique aligns Casey and Calley Means with RFK Jr.’s “Make America Healthy Again” movement, which Calley has been involved in as a policy advisor. This political association has complicated the reception of the book in some quarters — associating rigorous metabolic science with a politically controversial figure. The science in the book is, by and large, well-sourced and defensible; the political framing is a separate matter that readers should evaluate independently.
Good Energy is worth reading for its mechanistic explanations of metabolic dysfunction and its practical, evidence-grounded intervention framework — regardless of where you land on its political subtext. The core claim — that most chronic disease shares metabolic roots that are addressable through lifestyle change, and that the healthcare system is poorly designed to address those roots — is supported by substantial evidence and deserves serious engagement. The six biomarker framework gives readers a concrete starting point for assessing their own metabolic health without requiring specialised testing or medical referral. Start with your next blood panel, calculate where you sit on each marker, and let that data determine how urgent the interventions need to be.
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