Gordon I Smith

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This study compared the full lipid profiles in blood across lean insulin-sensitive people, obese insulin-sensitive people, and obese people with insulin resistance and fatty liver. Very few lipid differences separated lean from obese-but-insulin-sensitive participants, while insulin resistance with fatty liver was linked to higher levels of specific fats like triglycerides and diacylglycerols. Insulin resistance — not obesity alone — is the main driver of abnormal complex lipid patterns in the blood.

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A normal-weight woman with lipedema — a condition causing disproportionate lower-body fat — lost 11% of her body weight through diet, and the study measured where that fat came from. About 85% of the weight lost was fat, and upper- and lower-body fat decreased at the same rate, so the proportion of fat in the legs did not change. Weight loss does reduce lipedema-affected fat tissue, making it a valid treatment even for people with lipedema who are not overweight.

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Fat cells release tiny particles called extracellular vesicles into the bloodstream, and this study found that immune cells — mainly macrophages — act as gatekeepers that normally clear these particles before they accumulate. In obesity, those immune cells become less effective at clearing the particles, causing more fat-cell vesicles to circulate. Higher circulating vesicle levels may drive harmful signaling between organs that contributes to metabolic disease.

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Researchers randomly assigned adults with overweight or obesity and short sleep to either extend their sleep by about one hour per night or keep their usual schedule for six weeks. The group that extended sleep slept more consistently and reported better sleep quality, but their insulin sensitivity and blood sugar control did not improve compared to the group that changed nothing. Getting more sleep helps sleep health but does not fix the metabolic problems linked to short sleep in people with obesity.

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Women with obesity and lipedema were compared to weight-matched women without lipedema, then both groups underwent about 9% diet-induced weight loss. At baseline, women with lipedema had more leg fat, higher insulin sensitivity, and fat tissue in the thigh with more inflammation, fibrosis, and fewer lymphatic vessel signals than abdominal fat. Weight loss reduced leg fat and improved insulin sensitivity but did not reduce the inflammation or fibrosis in the affected tissue, suggesting lipedema involves lasting structural changes beyond what weight loss alone can fix.

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Ten people with obesity and type 2 diabetes underwent marked weight loss of 16–20%, which more than doubled their whole-body insulin sensitivity. The improvements were accompanied by reduced fat tissue scarring signals, lower levels of a clotting-related protein (PAI-1), and a dramatic decrease in tiny fat-cell particles that block insulin signaling in muscle. The findings point to changes in fat tissue biology — not just less fat mass — as a key reason weight loss restores insulin action.

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Standard metabolomics can identify only a fraction of molecules detected in biological samples because most have no reference standard to match against. This study used carbon-13 isotope labeling to create a new identification method based on how metabolites are biochemically made, rather than their molecular structure. The approach identified 62% of previously unknown peaks and discovered a new amino acid derivative — trimethylglycyl-lysine — that changes in human muscle after intensive lifestyle treatment.

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A protein called GPR65 senses acidity outside cells, and this study found it is more active in fat tissue from obese people and inversely related to insulin resistance. Mice without GPR65 — either throughout the body or only in immune cells — had better insulin sensitivity, less liver fat, and less inflammation. GPR65 signaling in macrophages appears to promote the inflammation that drives insulin resistance in obesity.

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Fat cells release tiny particles into the bloodstream that carry signals to other organs, and this study found that tissue-resident macrophages normally clear these particles and set their circulating levels. In obese mice and humans, this clearance is impaired, so more fat-cell particles accumulate — and their levels are linked to worse insulin sensitivity in the liver. Macrophages in fat tissue act as a control valve for how much fat-cell signaling reaches the rest of the body.

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This study developed a new method to separately measure insulin-driven and non-insulin-driven sugar disposal after a glucose drink across a range of metabolic states — from lean and healthy to obese with type 2 diabetes. As insulin action worsens, the body increasingly relies on non-insulin pathways to clear blood sugar, but these backup mechanisms are not sufficient to prevent high glucose in people with diabetes. Weight loss therapy restored the insulin-driven component.

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Oxytocin — a hormone known for its role in social bonding and childbirth — was found to be a key regulator of fat breakdown, and this study identified the surprising source: a specialized subset of sympathetic nerve cells in the periphery, not the brain. Blocking these nerves reduced the ability of fat tissue to release stored fat in both mice and humans. This means the peripheral nervous system has a direct role in controlling fat metabolism through oxytocin, opening new avenues for metabolic therapies.

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Certain fat-like molecules that build up in muscle — specifically a ceramide called C18:0 — are thought to block insulin action, and this study tested whether weight loss changes them. After 18% weight loss in people with obesity and type 2 diabetes, insulin sensitivity doubled, but only the C18:0 ceramide in the mitochondrial compartment of muscle decreased significantly. Reducing this specific ceramide pool may be one way weight loss improves muscle's response to insulin.

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A fat-tissue protein called lipin 1 helps store fat inside fat cells, and this study found that people with obesity have lower lipin 1 expression, which correlates with insulin resistance across multiple organs and more fat being made in the liver. Mice engineered to lack lipin 1 only in fat cells developed insulin resistance, fatty liver, and early liver disease — effects that got worse on a high-fat diet. Healthy fat storage in fat cells appears to protect the rest of the body from metabolic damage.

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Fatty liver disease is common but hard to measure without expensive MRI or invasive biopsy, so this study validated a new ultrasound-based fat measurement called VDFF against MRI as the gold standard. VDFF detected liver fat above 5% with 97–99% accuracy and correlated strongly with MRI measurements in both development and validation groups. This tool could make routine screening for fatty liver disease far more accessible and affordable.

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Researchers compared detailed metabolic measurements in adults with obesity who were metabolically healthy versus metabolically unhealthy, including tests of muscle, liver, and fat tissue function. People with metabolically healthy obesity had more favorable muscle and fat tissue biology, lower circulating fats and sugars throughout the day, and less oxidative stress than those with metabolically unhealthy obesity. These findings outline specific biological mechanisms that may explain why some people with obesity avoid the metabolic complications that others develop.

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Researchers measured how the body produces and clears glucose during fasting in 239 people with varying blood sugar levels, from lean and normal to obese with diabetes. In people with mildly elevated fasting blood sugar, glucose production and clearance were both elevated but matched each other; in those with diabetic-range fasting glucose, clearance was severely impaired. Poor glucose clearance — not just excess production — is a central driver of fasting high blood sugar in obesity.

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A fat-tissue enzyme called lipin 1 helps fat cells store fat properly, and this study found that its expression is lower in people with obesity and correlates with worse insulin sensitivity and more fat being made in the liver. Mice lacking lipin 1 specifically in fat cells developed fatty liver, insulin resistance, and signs of liver disease — especially on a high-fat diet. This shows that proper fat storage in fat cells is essential for preventing metabolic disease elsewhere in the body.

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A 6-week worksite-based intensive lifestyle program that provided all meals and included exercise sessions three times per week was tested against standard care in people with overweight or obesity and metabolic risk factors. The intensive program produced significant decreases in body weight, HbA1c, cholesterol, triglycerides, and blood pressure, along with better exercise tolerance, while standard care changed little. Providing all food and making the program convenient at work dramatically improved adherence and metabolic outcomes.

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Brain scans using fMRI showed that lean people have a positive brain response to tasting food in the reward center (dorsal striatum), while people with obesity and metabolic disease had a blunted or reversed response. The degree of brain response predicted how much people craved food, and weight loss partially restored normal responses in metabolically unhealthy individuals. Disrupted brain reward signaling in obesity may make it harder to feel satisfied after eating, creating a barrier to sustaining weight loss.

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In early fatty liver disease in humans, this study found that a specific type of immune cell — monocyte-derived macrophages recruited from the blood — accumulates in proportion to the degree of liver fat. Mouse models confirmed these recruited cells arrive before native liver macrophages decline and before liver damage occurs, and they appear to absorb fat. This early immune response to liver fat may be a key target for treating fatty liver disease before it progresses.

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A 25-year-old woman with rigorously confirmed metabolically healthy obesity gained 30 kg over 5 years, bringing her BMI from 37.7 to 49.6, yet her blood sugar, insulin sensitivity, liver fat, and cardiovascular markers all remained normal. Fat tissue showed mild increases in inflammation genes but no rise in circulating inflammatory proteins. This case provides direct evidence that some people are genuinely resistant to the metabolic harm of obesity and major weight gain.

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Researchers compared the metabolic effects of losing 10% of body weight through diet alone versus diet plus structured exercise in people with obesity and prediabetes. Those who exercised in addition to dieting had twice the improvement in whole-body insulin sensitivity and showed stronger changes in muscle genes related to energy metabolism and blood vessel growth. Adding regular exercise to a calorie-restricted diet produces substantially greater metabolic benefits than dieting alone in people with obesity and prediabetes.

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A protein channel called SWELL1 supports insulin signaling in fat, muscle, and pancreatic cells, and it is reduced in diabetic tissue. Using cryo-electron microscopy to map the channel's structure, researchers designed a drug-like molecule that restores SWELL1 protein levels and improved blood sugar control, reduced liver fat, and boosted insulin secretion in diabetic mice. This represents a new class of potential diabetes treatment targeting SWELL1.

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The liver makes glucose from amino acids in people with diabetes, worsening high blood sugar, and this study found that an enzyme called ALT2 is overexpressed in diabetic livers and drives this process. Knocking out ALT2 specifically in liver cells lowered blood glucose in diabetic mice without affecting lean mice. Targeting ALT2 in the liver could be a viable approach for reducing glucose production in type 2 diabetes.

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This study examined whether lifestyle habits explain why some obese people stay metabolically healthy while others do not, finding that metabolically healthy obese individuals performed about 45 more minutes of light physical activity per day than both lean and metabolically unhealthy obese individuals. Sleep duration, sleep quality, and diet showed no meaningful differences between the groups. Light daily movement — not diet or sleep — appears to be a key modifiable factor protecting against metabolic disease in obesity.

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Researchers carefully mapped how obesity, insulin resistance, and declining beta-cell function interact across five groups ranging from lean and healthy to obese with type 2 diabetes. Obesity itself — independent of insulin resistance — increased insulin secretion, and reduced insulin clearance amplified this effect to maintain normal blood sugar in moderately insulin-resistant people. It is a breakdown in beta-cell function, not worsening insulin resistance, that ultimately triggers impaired fasting glucose and type 2 diabetes.

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An 8-month intensive lifestyle program delivered at the worksite produced 17% average weight loss and broad metabolic improvements in 18 people with obesity and type 2 diabetes. Improvements spanned blood sugar control, insulin sensitivity in multiple organs, heart-lung fitness, muscle strength, and liver fat — linked to changes in muscle energy metabolism and fat tissue remodeling. Providing the program at work substantially improved adherence and demonstrates that intensive lifestyle therapy is feasible and highly effective.

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In people with obesity and fatty liver disease, fat tissue inflammation was higher and tiny fat-derived particles (exosomes) circulating in the blood blocked insulin signaling in muscle and liver cells in lab tests. However, the elevated inflammation in fat tissue did not translate into higher levels of most inflammatory proteins in the bloodstream. Both local fat tissue inflammation and circulating fat-derived exosomes appear to contribute to the whole-body insulin resistance seen in fatty liver disease.

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Hyaluronan is a sugar-based molecule found in tissue, and while high levels in the blood are associated with diabetes, this study found that producing more hyaluronan specifically inside fat cells actually protects mice from obesity and blood sugar problems on a high-fat diet. The improvement was tied to crosstalk between fat tissue and the liver rather than elevated blood hyaluronan levels. Blanket inhibition of hyaluronan production — proposed as a diabetes treatment — may backfire by harming fat tissue function.

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Researchers measured fat production and collagen production in belly fat tissue from lean people, obese people with healthy livers, and obese people with fatty liver disease. Fat tissue production capacity was equally high in both obese groups regardless of liver fat, while collagen production — a marker of tissue scarring — was elevated specifically in those with fatty liver and correlated with worse insulin sensitivity. Fatty liver in obesity is linked to fat tissue scarring, not to the fat tissue running out of room to store fat.

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Dopamine is released in the brain's reward center during food anticipation, and this study tested whether that response changes between fasting and fed states in people with obesity and prediabetes. After eating a full meal, these individuals showed no suppression of dopamine release when viewing high-calorie food images — a normal brain would suppress this signal after satiation. Impaired dopamine signaling in obesity may make it harder to stop eating once satisfied, contributing to overconsumption.

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A protein called Grb14 acts as a brake on insulin signaling, and previous work showed removing it from the whole body improves insulin action but causes heart problems. This study used a targeted gene-silencing approach to reduce Grb14 in liver and fat tissue in obese mice and found improved blood sugar control with no measurable effect on heart function. Selectively blocking Grb14 in metabolic tissues — while sparing the heart — may be a viable therapeutic strategy for type 2 diabetes.

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This study measured exactly how the liver and rest of the body handle insulin after a glucose drink in lean people versus those with obesity, with and without fatty liver disease. Obese people produced much more insulin, but the liver's maximum capacity to extract it is limited — so more insulin spills into the bloodstream, reaching muscle and other tissues. In obesity with fatty liver, this flood of insulin still cannot overcome the severe insulin resistance, explaining why blood sugar control breaks down.

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Fat tissue in people with obesity gets less oxygen than in lean people, and this study showed that lower oxygen levels correlated with worse insulin sensitivity and more fat tissue inflammation and scarring. Low oxygen in fat tissue was also tied to higher blood levels of branched-chain amino acids, which independently worsen insulin action. Reduced fat tissue oxygenation appears to be an upstream driver connecting obesity to multiple features of metabolic disease.

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This study investigated what drives fat buildup in the liver in people with fatty liver disease and whether weight loss reverses it. The liver's own fat production was three times higher in obese people with fatty liver compared to lean people, and this overproduction was tightly linked to elevated blood insulin and glucose levels. Losing 10% of body weight reduced liver fat by lowering the liver's fat production, identifying insulin resistance as the key driver.

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Glucagon raises blood sugar, and abnormally high glucagon is common in obesity and thought to worsen diabetes, but this study found that obese mice and humans actually respond to fasting with a blunted glucagon rise rather than an exaggerated one. In lean animals, fasting clearly raised glucagon; in obese animals, it did not — and refeeding briefly restored high glucagon. Obesity disrupts normal fasting-state glucagon regulation, which may make it harder for the body to respond appropriately to changes in eating.

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This review examines the concept of metabolically healthy obesity — why some obese people avoid diabetes, fatty liver, and cardiovascular disease while others do not — and finds that popular definitions are too loose, capturing many people who simply have fewer metabolic problems rather than true metabolic health. Evidence from animal studies points to differences in how fat tissue responds to weight gain as a likely explanation. The review argues that understanding true metabolic health in obesity requires more rigorous definitions and investigation of fat tissue biology.

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Reduced oxygen in fat tissue during obesity is thought to cause inflammation and metabolic problems, and this study identified increased oxygen demand by fat cells — driven by a protein called ANT2 — as the primary cause of that oxygen shortage. Removing ANT2 specifically from fat cells restored normal oxygen levels, reduced inflammation, and improved insulin resistance in obese mice. Reducing fat cell oxygen demand, rather than just boosting blood flow, may be a better strategy for treating obesity-related metabolic disease.

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This review synthesized 43 research articles on emergency nurse practitioners to examine how their training, experience, and scope of practice are reported and how patient outcomes are evaluated. Most studies were descriptive rather than experimental, and few provided details on practitioner training or practice parameters — making it impossible to explain why outcomes varied. Consistent reporting of practitioner characteristics and outcome measures is needed to build reliable evidence for the nurse practitioner role in emergency settings.

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Adding extra whey protein to the diet during weight loss in middle-aged postmenopausal women with obesity slightly reduced early muscle loss, but this effect disappeared by the time 10% weight loss was reached, and muscle strength was unaffected by the extra protein. The overall muscle loss with diet-induced weight loss was small in both groups. High protein supplementation during calorie-restriction weight loss does not provide meaningful protection of muscle in this population.

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This study tested the common belief that leucine, an amino acid in protein, is solely responsible for triggering muscle protein synthesis after eating protein. When women consumed protein or an equivalent dose of leucine alone during controlled insulin conditions, only protein — not leucine alone — increased muscle protein synthesis. Leucine activates signaling pathways but is not sufficient by itself; other amino acids in protein are also needed to fully build muscle.

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Researchers investigated why eating protein reduces the body's response to insulin, looking at a valine breakdown product (3-HIB) and the hormone FGF21 as potential mediators. Protein ingestion blocked the normal insulin-driven decrease in 3-HIB and increase in FGF21, while leucine alone did not affect insulin sensitivity. This implicates 3-HIB and FGF21 as part of the mechanism by which protein in the diet can temporarily blunt insulin action in humans.

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This study compared how gastric bypass surgery and gastric banding affect two gut hormones, FGF19 and FGF21, after eating. Both surgeries raised FGF19 after meals, but only bypass surgery — which reroutes food rapidly to the small intestine — uniquely elevated FGF21 after meals. The finding suggests the physical rearrangement of the gut in bypass surgery, not just weight loss itself, drives specific hormonal changes that may contribute to metabolic improvement.

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This review summarizes human studies on fish oil-derived omega-3 fatty acids and their effects on muscle in older adults, finding that 8–24 weeks of supplementation increases muscle protein synthesis, stimulates growth signaling pathways, and may increase muscle volume. Higher omega-3 levels in red blood cells are also linked to greater muscle strength and physical function. Omega-3 supplementation is a potentially low-cost strategy to slow age-related muscle loss.

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Eating a high-protein diet (1.2 g per kg per day) during weight loss in postmenopausal women with obesity reduced lean mass loss by about 45% compared to the standard recommended protein intake — but it also completely blocked the improvements in muscle insulin sensitivity and glucose uptake that weight loss normally produces. High protein intake also prevented beneficial changes in muscle oxidative stress and structural pathways. The protein content of a weight-loss diet matters: more protein preserves lean mass but appears to come at the cost of metabolic improvements.