PDF Summary:Lies I Taught in Medical School, by Robert Lufkin

For decades, mainstream medicine has told us that weight management is simply about calories in versus calories out, and that high cholesterol causes heart disease. In Lies I Taught in Medical School, Robert Lufkin challenges these assumptions and argues that the real culprits behind obesity and chronic disease are insulin and mTOR—two biological mechanisms that control how our bodies store energy and age.

Lufkin explains how modern eating patterns keep these mechanisms constantly activated, leading to metabolic dysfunction and diseases like diabetes, Alzheimer's, and cancer. He explores how dietary changes, fasting, and certain medications can help restore metabolic health by regulating insulin and mTOR. This guide covers the science behind metabolic syndrome, the role of different foods in triggering these pathways, and therapeutic approaches—including ketogenic diets—that may slow aging and prevent chronic illness.

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(Shortform note: Insulin and mTOR determine whether calories are burned or stored as fat by activating a series of signaling pathways inside cells. These pathways change which enzymes are active, steering nutrients into storage depots instead of being rapidly burned. Saxton and Sabatini explain that mTORC1 integrates signals from growth factors, nutrients, and cellular energy status through the PI3K–Akt–TSC–Rheb axis and the Rag GTPases to reprogram cellular metabolism. When activated, mTORC1 promotes increased uptake of glucose and amino acids, upregulates glycolysis and the pentose phosphate pathway, stimulates de novo synthesis of lipids, sterols, proteins, and nucleotides in part via SREBP and related transcriptional regulators, and simultaneously suppresses catabolic pathways such as autophagy and lysosomal protein degradation. mTORC2, acting downstream of PI3K, phosphorylates Akt to enhance glucose transport and glycogen synthesis while inhibiting FoxO-driven transcriptional programs associated with stress responses and oxidative metabolism.)

It senses sugars, the sugar-regulating hormone, IGF-1, oxygen, and the building blocks of protein. Once mTOR is switched on, it puts the body into growth mode, driving cellular proliferation. When deactivated, it puts the body in a state of repair, lowering inflammation, using stored energy and lipids as fuel, and creating ketones. It initiates catabolism. mTOR activation triggers amyloid-beta creation, which subsequently activates more mTOR. Inhibiting mTOR in rats has been found to stop Alzheimer's-like symptoms and reduce amyloid-beta levels, delaying the disease's development.

How mTOR Controls Growth and Repair

Robert A. Saxton and David M. Sabatini explain that mTOR controls whether cells build new components or clear out damaged ones. When mTOR is active, it tells cells to make proteins, lipids, and nucleotides, which are the building blocks for growth. At the same time, it stops the cell from recycling old or damaged parts. This happens at the lysosome, which is like the cell's recycling center. When mTOR is turned off, the cell switches to repair mode, cleaning up and reusing its components. This shift in cellular “cleanup” versus “construction” affects how much amyloid-beta builds up or gets removed.

In this section, we’ll explore dietary triggers of mTOR and insulin activation, as well as lifestyle and therapeutic approaches to modulating insulin and mTOR.

Dietary Triggers for Activating Insulin/mTOR

Lufkin explains that sugars like glucose and fructose can trigger insulin and mTOR activation. Glucose is the main sugar in the bloodstream, while fructose is a simple sugar found in fruit. Sucrose, or granulated sugar, combines glucose with fructose. HFCS is also a combination of glucose and fructose, but with a higher percentage of fructose.

Glucose spikes cause insulin spikes, which can lead to insulin resistance, fat storage, and mTOR activation. mTOR activation causes cell growth, increased cell production, and inflammation. The liver processes fructose and converts it into fat. It also leads to the liver and muscles becoming resistant to insulin.

(Shortform note: Luc Tappy and Kim-Anne Lê explain that the effects of fructose on the body depend on the amount consumed. They explain that the negative effects of fructose are only seen when it’s consumed in large amounts. When fructose is consumed in moderate amounts, it doesn’t have a significant impact on body weight, insulin sensitivity, or fasting blood lipids. This suggests that the negative effects of fructose are only seen when it’s consumed in large amounts, and that moderate consumption may not have the same negative effects.)

Lifestyle and Therapeutic Modulation of Insulin/mTOR

According to Lufkin, fasting and lifestyle changes can help regulate mTOR and insulin. When you fast, your body first depletes the liver's glycogen reserves. After about 12 hours, it starts using fat as fuel. This process decreases insulin and relieves your cells from constant insulin exposure. Fasting also turns off mTOR, which helps lessen resistance to insulin.

Lifestyle changes, such as adjusting your diet and eating habits, can also help regulate insulin and mTOR. By managing mTOR with lifestyle adjustments or medications such as rapamycin, we might be able to slow aging and its associated chronic illnesses, leading to additional years of well-being.

The History of Fasting and mTOR Inhibition

The idea of regulating insulin and mTOR through fasting, lifestyle changes, and drugs like rapamycin has a rich history. In the early 1900s, scientists discovered that rodents lived longer when they ate fewer calories. This finding sparked interest in how calorie restriction and fasting might extend lifespan. In the 1970s, researchers found a compound called rapamycin in soil samples from Easter Island. This drug could directly inhibit mTOR, a key protein involved in aging. These discoveries showed that changing how much we eat, making lifestyle adjustments, and using certain drugs could all target the same aging pathways. This laid the groundwork for using calorie restriction, lifestyle changes, and mTOR-targeting drugs to potentially extend healthy lifespan.

Lufkin also notes that substances like rapamycin and metformin can modulate mTOR and insulin for longevity benefits. Rapamycin is the best anti-aging drug on the market. It inhibits mTOR, increasing lifespan in every model organism, boosting function, and lowering pathology in virtually all mouse organs and tissues. It has been safely used by people for more than two decades for other purposes, but its impact on how long humans live is still unclear. Metformin is a primary medication used to manage type 2 diabetes. Alone, it minimally affects mortality, but when given with rapamycin, it extended median lifespan by 23% in mice.

(Shortform note: In a research article, scientists found that a compound that targets mTOR can extend the lifespan of mice. The study involved feeding the compound to mice and observing their survival rates compared to a control group. The results showed that the mice given the compound lived longer than those in the control group. This finding suggests that targeting mTOR could be a promising approach to increasing lifespan. The study provides valuable insights into the potential of mTOR-targeting compounds for promoting longevity and healthy aging.)

Metformin might be a therapeutic option for treating neurodegenerative diseases. Rapamycin seems to imitate the effects of calorie restriction and enhance autophagy, which enables it to slow down or potentially reverse aging. In animal tests, it postpones and even counteracts nearly all age-related illnesses or functional declines. Along with the persistent ailments discussed in the book, rapamycin also offers benefits for conditions like macular degeneration, mitochondrial disorders, muscle loss, stem cell function, and menopause.

(Shortform note: The study of metformin and rapamycin as potential treatments for age-related conditions is part of the broader field of geroscience. Geroscience is an interdisciplinary field that seeks to understand the relationship between aging and age-related diseases. It focuses on the molecular and cellular mechanisms that drive the aging process and how these mechanisms contribute to the development of chronic diseases. According to the authors, some of the key hallmarks of aging include genomic instability, loss of proteostasis, and cellular senescence.)

However, Lufkin warns that high doses of rapamycin can lead to oral ulcers, cataracts, hypertension, anemia, and diabetes. It can also raise the chances of infection, bleeding, and certain cancers, like skin cancer. At the low doses typically used in anti-aging trials, the drug seldom causes side effects beyond occasional mouth ulcers. While the book covers the positive outcomes of mTOR inhibition, it cautions against fully deactivating it. Activating mTOR increases protein creation and causes muscle hypertrophy. That's the process for developing muscle during exercise. Low mTOR levels may correlate with muscle atrophy. mTOR should probably be activated for people under 25 as they mature. This emphasizes how much we still need to discover in this field. Achieving longevity involves more than merely using rapamycin or other drugs.

mTOR Complexes

Saxton and Sabatini explain that mTOR forms two complexes, mTORC1 and mTORC2, which have different roles in the body. mTORC1 is involved in cell growth and metabolism, while mTORC2 helps regulate the cytoskeleton and cell survival. Rapamycin can inhibit both complexes, but the effects depend on the dose and duration of treatment. Low doses of rapamycin can extend lifespan in various organisms by partially inhibiting mTORC1, but complete loss of mTOR function is lethal. This suggests that carefully timed, low-dose rapamycin treatment might slow aging without completely shutting down mTOR activity, allowing for normal muscle growth and maintenance.

Metabolic Conditions Resulting From Insulin/mTOR Dysregulation

Pathological Consequences of Insulin/mTOR Dysregulation

Lufkin states that insulin and mTOR dysregulation may result in syndromes related to metabolism and other diseases. Metabolic syndrome is a group of symptoms that include obesity, elevated blood sugar, hypertension, low HDL cholesterol, and elevated triglycerides. Having a minimum of three symptoms indicates metabolic syndrome. Chronic mTOR activation leads to insulin insensitivity and persistent inflammation. Insulin resistance may cause illnesses such as diabetes (type 2), cancer, and cardiovascular conditions. Chronic inflammation leads to diseases such as Alzheimer's, arthritis, and cancer. mTOR activation also leads to cellular proliferation, which can lead to cancer.

(Shortform note: The insulin-mTOR pathway may not explain all cases of metabolic syndrome. In a 2023 review, Norbert Stefan, Hans-Ulrich Häring, and Frank B. Hu describe a phenotype called “metabolically healthy obesity.” These individuals have a lower risk of developing type 2 diabetes and cardiovascular disease than other obese individuals. They have normal insulin sensitivity and low levels of systemic inflammation. The authors note that this phenotype can persist for many years, suggesting that the insulin-mTOR pathway may not be the primary driver of metabolic dysfunction in these cases.)

Eating, especially high-carbohydrate foods, activates mTOR. Contemporary eating habits keep mTOR constantly activated, promoting growth while allowing unchecked aging and decay. In the past, fasting would deactivate metabolism, allowing for bodily repairs and autophagy. However, nowadays, we eat more frequently, and what we ingest isn't much better. Foods rich in carbohydrates are ideal for mTOR activation. We're constantly in an anabolic state of growth when what we need is a catabolic state to eliminate damaged cells and mend them.

(Shortform note: The International Olympic Committee (IOC) has a consensus group called RED-S (Relative Energy Deficiency in Sport) that argues that athletes should remain in an anabolic state. According to Mountjoy et al., prolonged catabolic states can suppress anabolic hormones, disrupt reproductive function, impair bone formation, and increase the risk of stress fractures. They recommend that athletes maintain adequate energy availability to support normal endocrine function, bone health, and optimal training adaptations.)

Therapeutic Approaches to Restore Metabolic Health

Lufkin argues that metabolic therapy, such as following a keto eating plan, can help restore metabolic health. A ketogenic diet is a high-fat, low-carb eating plan that mimics fasting and causes the body to use ketones for energy instead of glucose. Humans prospered in a beneficial nutritional condition known as ketosis for two and a half million years, up until around twelve millennia ago with the Agricultural Revolution. Our metabolism developed to flourish while in ketosis.

(Shortform note: While Lufkin argues that ketosis is a natural and beneficial state for humans, some people have inherited disorders of mitochondrial fatty-acid oxidation that make ketosis dangerous. For these individuals, a ketogenic diet can trigger life-threatening metabolic decompensation. These disorders prevent the body from properly breaking down fats for energy, leading to the accumulation of toxic byproducts and severe energy deficits. Symptoms can include hypoglycemia, muscle breakdown, liver dysfunction, and even coma. For these patients, a ketogenic diet can be life-threatening rather than metabolically restorative.)

Ketones supply greater energy than glucose and don't set off a range of long-term illnesses. They're readily utilized by the cardiac muscles and kidneys for energy, and ketones can penetrate the blood-brain barrier to fuel the brain. Ketone bodies generate a higher quantity of adenosine triphosphate than glucose, enabling the body to efficiently generate fuel even with fewer calories. They also reduce damage from free radicals and enhance antioxidant capacity. A keto diet provides substantial health advantages. A study had a group of participants follow a ketogenic diet for three days. Over just those few days, they lost weight, improved their sensitivity to insulin, and lowered inflammation. Ketosis isn't a passing health trend. It is a way of living that will enhance long-term health and lifespan.

Keto and Bone Health

While the ketogenic diet has been shown to have many health benefits, there are some potential risks associated with long-term adherence to the diet. One concern is the impact on bone health. Some studies have found that people who follow a strict ketogenic diet for extended periods may experience a decrease in bone mineral density, which can increase the risk of fractures and osteoporosis. This is thought to be due to the diet's potential to cause metabolic acidosis, which can lead to the leaching of calcium from bones. Additionally, the diet's restriction of certain foods that are important for bone health, such as fruits, vegetables, and dairy products, may contribute to this effect. However, it's important to note that the impact of the ketogenic diet on bone health may vary depending on individual factors such as age, sex, and overall health status. Some studies have found that the diet may not have a significant impact on bone health in the short term, but the long-term effects are still not fully understood.