Part 11
Metabolism, Insulin Resistance, and the GLP-1 Era
ILLUSTRATION. A woman has lost substantial weight on a weekly injection. Her knees hurt less and her blood pressure has improved, but some days she struggles to eat enough and her strength is falling. The next decision is about the whole treatment: dose, nutrition, function, and maintenance. A successful weight-loss number can be the beginning of a better plan rather than the end of the visit.
Clinical scenes in this edition are explicitly labeled illustrations. They describe imagined situations used to explain medical decisions, not documented patients, diagnoses, conversations, or treatment outcomes. They should not be read as evidence that a particular intervention works. Personal recollections are recollections, not medical records.
Evidence grade (draft mapping). 23 questions; a question with mixed evidence counts under each grade.
- 137. What is metabolic health, and how do I know if I have it?It means your body handles sugar and fat properly. Five simple measures tell you, and most American adults fail at least one.GGuideline-based / consensus
- 138. What is insulin resistance?Insulin resistance means the body needs more insulin to produce a given effect. It may develop before glucose reaches the diabetes range, but one insulin result cannot reliably diagnose or rank everyone.EEstablished clinical knowledge
- 139. Can prediabetes be reversed?Glucose levels can return below the prediabetes range, and progression can often be delayed. In a major prevention trial, intensive lifestyle change outperformed metformin on average.ARobust human trials
- 140. How do I test for insulin resistance?For most people, begin with clinical risk assessment and established glucose tests. Routine fasting insulin and HOMA-IR screening are not recommended by the ADA/AACC laboratory guideline.GGuideline-based / consensus
- 141. What causes insulin resistance?Mostly fat stored in the wrong places, the liver, the pancreas, and around the organs, combined with reduced muscle function or activity, too little movement, and too little sleep.DPreclinical / mechanistic
- 142. Can a thin person be insulin resistant?Yes. Doctors sometimes call it “thin outside, fat inside.”EEstablished clinical knowledge
- 143. What is the fastest way to reverse insulin resistance?Lose fat from the liver, build muscle, and move after meals. Improvement shows up within days to weeks.ARobust human trials
- 144. Can type 2 diabetes itself be reversed?Often, yes, especially in the first several years. The key is substantial weight loss.ARobust human trials
- 145. Does insulin resistance affect the brain and cancer risk?Yes. It raises the risk of dementia and of several cancers.CObservational
- 146. What is PCOS, and is it a longevity issue?Polycystic ovary syndrome is a common hormonal condition in women, driven largely by insulin resistance. It raises lifetime risk of diabetes, fatty liver, and probably heart disease.GGuideline-based / consensus
- 147. What are GLP-1 medicines, in plain language?They copy a natural gut hormone that tells the brain you are full, slows the stomach, and helps the pancreas control sugar.ARobust human trials
- 148. Do they do more than cause weight loss?Yes. In people with obesity and heart disease, semaglutide cut heart attacks, strokes, and cardiac deaths by 20 percent, and the benefit appeared before much weight was lost.ARobust human trials
- 149. What are the real risks?Nausea, constipation or diarrhea, and reflux are common, especially early. Gallstones, pancreatitis, and severe stomach slowing are uncommon but real. I also pay close attention to nutritional adequacy, strength, and function during weight loss.RRegulatory status
- 150. How do I keep my muscle while losing weight on these drugs?Combine progressive resistance training with adequate nutrition, and follow function as well as weight. These measures support muscle; they cannot guarantee that none will be lost.GGuideline-based / consensus
- 151. Do I have to take them forever?For most people, the weight returns when the drug stops. Think of it like blood pressure medicine: it works while you take it.ARobust human trials
- 152. Should a lean, healthy person “microdose” a GLP-1 for longevity?The evidence does not yet justify it.FNot demonstrated / insufficient
- 153. What should I take and do while on a GLP-1 medicine?Plan food, activity, side-effect management, and follow-up with the prescriber. There is no mandatory supplement stack for every GLP-1 user.GGuideline-based / consensus
- 154. What if I do not lose weight on a GLP-1?You are not doing it wrong. About one in ten people respond poorly to a given drug, for biological reasons.GGuideline-based / consensus
- 155. I read that these drugs can cause blindness. Should I stop?Do not stop effective treatment because of a headline. There is a rare optic-nerve condition associated with semaglutide that deserves a clear discussion, especially if you have a relevant history.CObservational
- 156. What is new in 2026?A daily pill and a more powerful injection.RRegulatory status
- 157. Should healthy people take metformin for longevity?Not yet. The trial designed to answer that question has still not been completed, and metformin may blunt some benefits of exercise.FNot demonstrated / insufficient
- 158. What about SGLT2 inhibitors?These diabetes pills turned out to protect the heart and kidneys in people with and without diabetes. They are proven medicines for those conditions, not general anti-aging pills.ARobust human trials
- 159. What is fatty liver, and why should I care?Fat stored in the liver is now the most common liver disease in the world, affecting roughly one in three adults. It is an early warning for diabetes and heart disease, and it is reversible.CObservational