Metabolic Health Glossary

Also known as: HbA1c, glycated hemoglobin, glycosylated hemoglobin

A blood test that measures the average blood sugar level over the past 2-3 months by assessing the percentage of hemoglobin with attached glucose. Normal is below 5.7%, prediabetes is 5.7-6.4%, and diabetes is 6.5% or above. A1C provides a longer-term picture than a single fasting glucose test.

Sugars and syrups added to foods during processing or preparation, as opposed to sugars naturally present in whole foods like fruit. The American Heart Association recommends limiting added sugars to 25g (women) or 36g (men) per day. Excess added sugar drives insulin resistance, promotes visceral fat storage, and feeds harmful gut bacteria.

Signaling molecules released by fat tissue that influence metabolism, inflammation, and insulin sensitivity. Pro-inflammatory adipokines (TNF-alpha, IL-6, resistin) from visceral fat promote insulin resistance, while anti-inflammatory adipokines (adiponectin) improve insulin sensitivity. The balance shifts toward inflammation as visceral fat increases.

A hormone released by fat cells that improves insulin sensitivity, has anti-inflammatory properties, and is protective against metabolic disease. Paradoxically, adiponectin levels are lower in people with excess body fat (especially visceral fat). Weight loss, exercise, and omega-3 fatty acids increase adiponectin levels.

Also known as: advanced glycation end products

Harmful compounds formed when proteins or fats combine with sugars (glycation). AGEs accumulate from both internal high blood sugar and external sources (foods cooked at high temperatures, especially grilled/fried meats). They increase oxidative stress, promote inflammation, and accelerate vascular damage. Lower-temperature cooking methods reduce dietary AGE formation.

An enzyme activated during exercise and fasting that acts as a cellular energy sensor. AMPK activation triggers GLUT4 translocation to the cell surface (allowing glucose entry without insulin), increases fat oxidation, and improves mitochondrial function. It is a key mechanism by which exercise improves blood sugar independently of insulin.

Acetic acid-containing vinegar that research suggests can reduce postprandial glucose by 20-30% when consumed before or with a carbohydrate-containing meal. The acetic acid appears to slow gastric emptying and inhibit certain carbohydrate-digesting enzymes. Typically used as 1-2 tablespoons diluted in water before meals.

The body's cellular recycling process that breaks down and recycles damaged proteins, dysfunctional mitochondria, and cellular debris. Autophagy is upregulated during fasting when nutrient-sensing pathways like mTOR are suppressed and AMPK is activated. It supports metabolic health by improving cellular function, reducing inflammation, and clearing dysfunctional components.

A plant alkaloid found in several herbs that has been shown in research to lower blood sugar through AMPK activation, similar to the mechanism of metformin. It improves insulin sensitivity, reduces hepatic glucose production, and supports beneficial gut bacteria. Used as a supplement for blood sugar management, though it should be discussed with a healthcare provider due to drug interactions.

The insulin-producing cells located in the islets of Langerhans in the pancreas. In the progression from insulin resistance to type 2 diabetes, beta cells initially compensate by producing more insulin, but over time they become exhausted and fail, leading to declining insulin production and rising blood sugar.

High-energy visible light (400-500nm) emitted by screens, LED lights, and the sun. Evening blue light exposure suppresses melatonin production and directly impairs glucose tolerance the following day. Using blue light blocking glasses, enabling night mode on devices, or avoiding screens 1-2 hours before bed helps protect both sleep quality and metabolic health.

Also known as: body mass index

A calculation based on weight and height (weight in kg / height in meters squared) used as a population-level screening tool. While useful for broad categorization, BMI does not distinguish between muscle and fat, nor between visceral and subcutaneous fat. A muscular person may have a 'high' BMI with excellent metabolic health, while a 'normal' BMI person may have dangerous visceral fat.

The proportions of fat, muscle, bone, and water that make up body weight. Body composition is more relevant to metabolic health than total body weight. Favorable body composition (more muscle, less visceral fat) improves insulin sensitivity regardless of what the scale shows. Resistance training and adequate protein intake improve body composition.

Macronutrients that break down into glucose during digestion, having the most direct impact on blood sugar of all nutrients. Types range from simple sugars (fast-absorbing, high blood sugar impact) to complex carbohydrates with fiber (slower-absorbing, lower impact). Quality and quantity of carbohydrates are key considerations for metabolic health.

A trace mineral that enhances insulin's action by helping insulin receptors function more effectively. Chromium picolinate supplementation has shown modest improvements in A1C and fasting glucose in some studies. Found in broccoli, green beans, whole grains, and nuts. Requirements are small but deficiency may worsen insulin resistance.

Prolonged activation of the stress response, whether from psychological stressors (work, relationships, financial pressure), physiological stressors (poor sleep, overexercise, chronic pain), or environmental stressors. Chronic stress keeps cortisol chronically elevated, which directly promotes insulin resistance, visceral fat accumulation, inflammation, and impaired immune function.

The internal 24-hour biological clock that regulates sleep-wake cycles, hormone release, body temperature, and metabolic processes. Circadian rhythm directly governs the timing of insulin secretion, cortisol release, and glucose metabolism. Disrupting circadian rhythm through irregular sleep, shift work, or late-night eating impairs metabolic function even when total sleep hours are adequate.

A small sensor worn on the body (typically the arm) that measures interstitial glucose levels every few minutes, providing 24/7 data. For people with prediabetes, CGMs reveal real-time glucose responses to specific foods, exercise, stress, and sleep. This enables personalized nutrition and lifestyle decisions rather than relying on generic advice. Increasingly available without prescription.

The body's primary stress hormone, produced by the adrenal glands. Cortisol follows a circadian pattern—highest in the morning (helping wake you up) and lowest at night. Cortisol raises blood sugar by stimulating gluconeogenesis, reduces insulin sensitivity, and promotes visceral fat storage. Chronic elevation from poor sleep, stress, or disrupted circadian rhythm directly worsens metabolic health.

A natural rise in blood sugar that occurs in the early morning hours (typically 4-8 AM), caused by overnight release of cortisol, growth hormone, and glucagon that stimulate the liver to release glucose. In people with insulin resistance, the body cannot adequately suppress this glucose release, leading to elevated morning fasting glucose readings.

Also known as: slow-wave sleep, N3 sleep

The most restorative sleep stage (slow-wave sleep/N3), when growth hormone is released, tissues repair, the immune system strengthens, and the glymphatic system clears brain metabolic waste. Deep sleep is essential for next-day insulin sensitivity and glucose regulation. It is most abundant in the first half of the night and decreases with age, alcohol, and blue light exposure.

Also known as: DPP

A landmark NIH-funded clinical trial showing that lifestyle intervention (150 minutes per week of moderate exercise and 5-7% weight loss) reduced the progression from prediabetes to type 2 diabetes by 58%—nearly twice as effective as the medication metformin (31% reduction). The results were consistent across all ethnicities and age groups, with even greater benefit in adults over 60.

Also known as: deep breathing, belly breathing

Deep belly breathing that engages the diaphragm, activating the parasympathetic nervous system and directly lowering cortisol. A simple technique: inhale for 4 counts through the nose (expanding the belly), hold for 4 counts, exhale for 6-8 counts through the mouth. Even 5-10 minutes of diaphragmatic breathing measurably reduces cortisol levels and can improve acute blood sugar response.

The period of time each day during which food is consumed in a time-restricted eating pattern. Common windows range from 6 to 12 hours. Earlier eating windows (e.g., 8am-4pm) appear to offer greater metabolic benefits than later windows due to alignment with circadian rhythm—insulin sensitivity and glucose tolerance are naturally higher earlier in the day.

A diagnostic dietary approach that temporarily removes suspected problem foods (common triggers include gluten, dairy, soy, corn, eggs), then reintroduces them systematically to identify which foods may be causing inflammation, digestive issues, or blood sugar dysregulation. Should be done under professional guidance for best results.

Changes in gene expression that don't alter the DNA sequence itself, often influenced by lifestyle and environmental factors. Diet, exercise, sleep, stress, and environmental exposures can turn genes 'on' or 'off.' Epigenetic changes can influence metabolic health and insulin sensitivity, and some may be passed to future generations. This means lifestyle choices have deeper effects than simply 'burning calories.'

Brief bouts of physical activity (2-5 minutes) performed throughout the day to break up prolonged sitting. Research shows breaking up sedentary time with even 2-3 minutes of activity every 30-60 minutes significantly improves blood sugar control and insulin sensitivity compared to continuous sitting, even when total daily exercise time is equivalent.

Also known as: fasting blood glucose, FBG, fasting plasma glucose

A blood sugar measurement taken after at least 8 hours of fasting. Normal fasting glucose is below 100 mg/dL. Prediabetes is 100-125 mg/dL, and diabetes is 126 mg/dL or above on two separate tests. It's a standard screening tool but may miss early insulin resistance.

A blood test measuring insulin levels after an overnight fast. Elevated fasting insulin (generally above 8-10 uIU/mL) indicates the pancreas is working harder than normal to maintain blood sugar, suggesting insulin resistance. This test can detect metabolic dysfunction years before fasting glucose or A1C become abnormal.

The process of burning stored fat for energy. During fasting or low-carbohydrate states, insulin levels drop, allowing fat cells to release fatty acids that are then oxidized (burned) by mitochondria for energy. Improving fat oxidation capacity through exercise and time-restricted eating is a key component of restoring metabolic flexibility in insulin-resistant individuals.

Indigestible carbohydrates that slow glucose absorption, feed beneficial gut bacteria, and improve satiety. Soluble fiber (oats, legumes, apples) forms a gel that slows digestion. Insoluble fiber (vegetables, whole grains) adds bulk. Adults should aim for 25-30g daily, but most consume only about 15g. Fiber is one of the most effective dietary tools for blood sugar management.

A blood test measuring average blood sugar over the past 2-3 weeks (shorter window than A1C). Useful for tracking rapid changes from dietary or lifestyle interventions, and in conditions that affect A1C accuracy (hemoglobin variants, anemia, recent blood loss). Provides faster feedback on the effectiveness of metabolic health changes.

The 'hunger hormone' produced primarily in the stomach that stimulates appetite. Sleep deprivation increases ghrelin levels, driving increased hunger and cravings for high-calorie, high-carbohydrate foods. This is one mechanism by which poor sleep promotes weight gain and worsens metabolic health.

An incretin hormone released by the gut after eating that stimulates insulin secretion, suppresses glucagon, slows gastric emptying, and promotes satiety. GLP-1 receptor agonist medications (semaglutide/Ozempic, liraglutide) mimic this hormone for diabetes and weight management. Natural GLP-1 release is enhanced by fiber, protein, and healthy gut bacteria.

A hormone produced by alpha cells in the pancreas that raises blood sugar by signaling the liver to release stored glucose (glycogen) and produce new glucose (gluconeogenesis). Glucagon works in opposition to insulin, and their balance determines blood sugar levels. In insulin resistance, glucagon signaling may become dysregulated, contributing to elevated fasting glucose.

Also known as: blood glucose meter

A portable device for measuring blood sugar using a small blood sample from a finger prick. Useful for spot-checking blood sugar levels, especially before and after meals. While less comprehensive than a CGM, periodic glucometer readings (particularly 1-2 hours after meals) provide valuable feedback on how specific foods affect your blood sugar.

The process by which the liver produces new glucose from non-carbohydrate sources (amino acids, glycerol, lactate). This process is normally suppressed after eating by insulin, but in insulin resistance, the liver continues producing glucose even when blood sugar is already elevated—a phenomenon called hepatic insulin resistance.

Also known as: OGTT, oral glucose tolerance test

A diagnostic test where blood sugar is measured before and after consuming a standardized glucose drink (typically 75g). Measures how efficiently the body clears glucose from the blood. A 2-hour reading of 140-199 mg/dL indicates prediabetes; 200+ indicates diabetes. Can detect impaired glucose tolerance that fasting tests miss.

Also known as: glycemic variability

The fluctuations in blood sugar levels throughout the day, including spikes after meals and drops between meals. High glucose variability—large swings between highs and lows—is associated with increased oxidative stress, inflammation, and cardiovascular risk, independent of average blood sugar levels.

The insulin-responsive glucose transporter found primarily in muscle and fat cells. When insulin binds to cell receptors, GLUT4 moves to the cell surface to allow glucose entry. Importantly, exercise activates GLUT4 independently of insulin through AMPK activation, which is why physical activity improves blood sugar even in insulin-resistant individuals.

The process by which sugar molecules attach to proteins and fats, forming harmful compounds called Advanced Glycation End Products (AGEs). Glycation is accelerated by high blood sugar and contributes to aging, cardiovascular damage, and diabetic complications. A1C itself is a glycated protein. Reducing blood sugar spikes reduces glycation.

A ranking system from 0-100 that measures how quickly a carbohydrate-containing food raises blood sugar compared to pure glucose (GI=100). Low GI (55 or below) foods include most vegetables, legumes, and berries. High GI (70+) foods include white bread, white rice, and sugary foods. Useful for food selection but should be considered alongside glycemic load.

A measure that accounts for both the glycemic index and the amount of carbohydrates in a typical serving, giving a more practical picture of a food's blood sugar impact. GL = (GI x grams of carbs per serving) / 100. Low GL is 10 or under; high GL is 20 or above. For example, watermelon has a high GI (72) but low GL (4) because a serving has few carbs.

The stored form of glucose, primarily in the liver and muscles. The liver releases glycogen as glucose between meals to maintain blood sugar, while muscle glycogen fuels exercise. Glycogen storage capacity is limited (about 400-500g total), and excess glucose beyond this capacity is converted to fat.

The brain's waste-clearing system, most active during deep sleep. It removes metabolic waste products including beta-amyloid (associated with Alzheimer's). Poor sleep reduces glymphatic clearance, and chronic sleep deprivation may accelerate neurodegeneration. This is one of many reasons adequate sleep is non-negotiable for long-term health.

The bidirectional communication network between the gastrointestinal tract and the brain, involving neural (vagus nerve), hormonal, and immunological pathways. The gut produces 90% of serotonin and influences mood, cognition, appetite, and stress response. Metabolic health is intimately connected to gut-brain signaling.

Also known as: high-density lipoprotein

High-density lipoprotein, often called 'good' cholesterol because it helps remove cholesterol from arteries. Low HDL (below 40 for men, 50 for women) is a component of metabolic syndrome. HDL is increased by exercise, healthy fats, and moderate alcohol, and decreased by refined carbohydrates, trans fats, and sedentary behavior.

Fats that support metabolic health, including monounsaturated fats (olive oil, avocados, nuts), omega-3 fatty acids (fatty fish, walnuts, flaxseed), and some saturated fats from whole foods. Healthy fats improve insulin sensitivity, reduce inflammation, support cell membrane integrity, and have minimal direct impact on blood sugar while slowing glucose absorption when paired with carbohydrates.

The variation in time intervals between consecutive heartbeats, reflecting the balance between sympathetic and parasympathetic nervous system activity. Higher HRV indicates greater stress resilience, better autonomic balance, and is associated with improved insulin sensitivity and lower inflammation. HRV improves with meditation, exercise, quality sleep, and stress management practices.

See A1C. The percentage of hemoglobin molecules in red blood cells that have glucose attached. Since red blood cells live about 120 days, A1C reflects the average blood sugar over the preceding 2-3 months. It can be affected by conditions that alter red blood cell lifespan.

A specific form of insulin resistance affecting the liver, where the liver fails to suppress glucose production in response to insulin. This means the liver continues releasing glucose into the blood even when blood sugar is already elevated—a major contributor to elevated fasting glucose in prediabetes and type 2 diabetes. Strongly associated with NAFLD.

Also known as: high-intensity interval training

Exercise alternating between short bursts of intense effort (80-95% max heart rate) and recovery periods. HIIT improves insulin sensitivity, increases mitochondrial capacity, and enhances VO2 max in less time than steady-state cardio. Studies show significant metabolic benefits with as little as 3 sessions per week of 20-30 minutes.

Also known as: Homeostatic Model Assessment

Homeostatic Model Assessment of Insulin Resistance—a calculation using fasting glucose and fasting insulin levels to estimate insulin resistance. A HOMA-IR below 1.0 is considered optimal, 1.0-2.0 suggests early insulin resistance, and above 2.0 indicates significant insulin resistance. It is one of the most sensitive early markers of metabolic dysfunction.

The concept that mild stress (exercise, fasting, cold exposure, certain plant compounds) triggers adaptive responses that make the body stronger and more resilient. Exercise stresses muscles, which respond by growing stronger. Fasting depletes energy stores, which triggers autophagy and improved insulin sensitivity. The key is appropriate dose—too little has no effect, too much causes harm.

Also known as: hypothalamic-pituitary-adrenal axis

The Hypothalamic-Pituitary-Adrenal axis—the body's central stress response system. When the brain perceives stress, the hypothalamus signals the pituitary gland, which signals the adrenal glands to release cortisol. Chronic HPA axis activation from ongoing stress leads to sustained cortisol elevation, which raises blood sugar, promotes visceral fat, and drives insulin resistance.

A blood marker measuring systemic inflammation, produced by the liver in response to inflammatory signals. Levels below 1.0 mg/L indicate low risk, 1.0-3.0 is moderate, and above 3.0 is high. Elevated hs-CRP is associated with insulin resistance, cardiovascular disease, and metabolic syndrome. It responds to lifestyle interventions including exercise, weight loss, and dietary changes.

Abnormally high levels of insulin in the blood, typically the body's compensatory response to insulin resistance. The pancreas produces more insulin to force glucose into resistant cells. Chronic hyperinsulinemia promotes fat storage, inflammation, and is a precursor to eventual pancreatic beta cell exhaustion and type 2 diabetes.

Gut hormones (primarily GLP-1 and GIP) released after eating that enhance insulin secretion in a glucose-dependent manner, slow gastric emptying, and suppress appetite. Incretin effect accounts for up to 50-70% of insulin secretion after a meal. This system may be impaired in type 2 diabetes and is the target of several diabetes medications.

The immune system's response to injury or threat. Acute inflammation is protective and healing. Chronic low-grade inflammation—driven by visceral fat, poor diet, stress, poor sleep, and gut dysbiosis—is a central driver of insulin resistance and metabolic disease. Inflammatory markers like hs-CRP and IL-6 are associated with metabolic dysfunction.

A measure of how much insulin the body releases in response to a given food, which can differ from the glycemic index. Some foods like dairy produce a high insulin response despite moderate blood sugar impact. Understanding the insulin index helps optimize food choices for people focused on reducing chronically elevated insulin levels.

A protein on the surface of cells that binds insulin and initiates the signaling cascade for glucose uptake. In insulin resistance, insulin receptors may be downregulated (fewer receptors) or their downstream signaling impaired. Regular exercise and weight loss improve insulin receptor function and sensitivity.

A condition where cells in the body become less responsive to the hormone insulin, requiring the pancreas to produce more insulin to maintain normal blood sugar levels. Insulin resistance is the root driver of prediabetes and type 2 diabetes, and is linked to cardiovascular disease, fatty liver, PCOS, and metabolic syndrome.

The degree to which cells respond effectively to insulin's signal to absorb glucose. High insulin sensitivity means cells respond well to even small amounts of insulin. Insulin sensitivity is improved by exercise, quality sleep, stress management, and healthy body composition, and worsened by sedentary behavior, poor sleep, chronic stress, and excess visceral fat.

The chain of molecular events triggered when insulin binds to its receptor on a cell surface, ultimately resulting in GLUT4 translocation and glucose uptake. In insulin resistance, defects at various points in this cascade impair the cell's response to insulin. Exercise and weight loss can improve signaling efficiency at multiple points in the cascade.

Also known as: IF

An eating pattern that cycles between periods of fasting and eating. Common approaches include time-restricted eating (daily eating window), 5:2 (normal eating 5 days, reduced calories 2 days), and alternate-day fasting. Benefits for metabolic health include improved insulin sensitivity, reduced fasting insulin, enhanced autophagy, and better body composition.

Also known as: leaky gut, increased permeability

A condition where the gut lining becomes more permeable than normal, allowing bacterial endotoxins (lipopolysaccharides/LPS) to enter the bloodstream. This triggers chronic low-grade inflammation (metabolic endotoxemia) that directly promotes insulin resistance. Caused by poor diet, chronic stress, alcohol, NSAIDs, and dysbiosis. Supported by fiber, fermented foods, and stress management.

Also known as: ketone bodies

Molecules produced by the liver from fatty acids during fasting, carbohydrate restriction, or extended exercise when glucose availability is low. Ketones (beta-hydroxybutyrate, acetoacetate, acetone) serve as alternative fuel for the brain and muscles. Low-level ketone production during overnight fasts indicates healthy metabolic flexibility. Ketones also have anti-inflammatory and neuroprotective properties.

Also known as: low-density lipoprotein

Low-density lipoprotein, traditionally called 'bad' cholesterol. However, LDL particle size matters: large, buoyant LDL is relatively benign, while small, dense LDL is more atherogenic (artery-damaging). Insulin resistance shifts LDL toward the small, dense pattern. Advanced testing (NMR lipoprofile) can measure particle size and number for better risk assessment.

A hormone produced by fat cells that signals satiety (fullness) to the brain. Sleep deprivation decreases leptin levels, reducing the feeling of fullness after meals. In obesity, leptin resistance can develop (similar to insulin resistance), where the brain no longer responds effectively to leptin's satiety signal.

A blood test measuring cholesterol and triglyceride levels. A standard panel includes total cholesterol, LDL, HDL, and triglycerides. For metabolic health, the triglyceride-to-HDL ratio is particularly informative—a ratio below 2.0 is ideal, while above 3.0 suggests significant insulin resistance. Advanced panels measuring LDL particle size and number provide additional cardiovascular risk information.

Blood markers indicating liver health. Alanine aminotransferase (ALT) is particularly relevant for metabolic health—elevated ALT can indicate non-alcoholic fatty liver disease (NAFLD), which is strongly associated with insulin resistance. Even 'high-normal' ALT values may indicate early fatty liver. ALT levels respond to lifestyle interventions.

The three main categories of nutrients that provide calories: carbohydrates, proteins, and fats. Each macronutrient affects blood sugar differently—carbohydrates have the most direct impact, protein has a moderate effect, and fat has minimal direct impact but slows absorption of other nutrients when eaten together.

An essential mineral involved in over 300 enzymatic reactions including glucose metabolism, insulin signaling, and blood pressure regulation. Magnesium deficiency is common and associated with increased insulin resistance. Found in leafy greens, nuts, seeds, dark chocolate, and avocados. Supplementation (glycinate or threonate forms) may improve insulin sensitivity and sleep quality.

The order in which you eat different components of a meal, which significantly affects the blood sugar response. Research shows eating vegetables first, followed by protein and fat, and carbohydrates last can reduce the postprandial glucose spike by up to 73% compared to eating carbohydrates first. This is a simple, free strategy for blood sugar management.

A dietary pattern emphasizing vegetables, fruits, whole grains, legumes, nuts, olive oil, and fish, with moderate dairy and limited red meat and processed foods. One of the most studied dietary patterns for metabolic health, associated with reduced insulin resistance, lower cardiovascular risk, and decreased progression from prediabetes to type 2 diabetes.

A hormone produced by the pineal gland that regulates sleep-wake cycles and has direct metabolic effects. Melatonin production increases in darkness and is suppressed by light, especially blue light from screens. Beyond sleep, melatonin plays a role in insulin secretion and glucose metabolism—evening light exposure that suppresses melatonin impairs glucose tolerance the following day.

The condition where bacterial endotoxins (lipopolysaccharides/LPS) from the gut enter the bloodstream due to increased intestinal permeability. These endotoxins trigger an immune response causing chronic low-grade inflammation that directly promotes insulin resistance. High-fat, high-sugar diets low in fiber increase metabolic endotoxemia; fiber-rich diets with fermented foods reduce it.

The body's ability to efficiently switch between burning carbohydrates and fats for fuel depending on availability and demand. Metabolically flexible people can easily use fat during fasting and carbohydrates after meals. Insulin resistance impairs metabolic flexibility, trapping the body in a carb-dependent state. Exercise and time-restricted eating improve metabolic flexibility.

Also known as: syndrome X, insulin resistance syndrome

A cluster of interconnected metabolic risk factors that together significantly increase the risk of type 2 diabetes and cardiovascular disease. Diagnosed when three or more are present: elevated waist circumference, elevated triglycerides (150+ mg/dL), reduced HDL cholesterol, elevated blood pressure (130/85+), and elevated fasting glucose (100+ mg/dL).

The most commonly prescribed medication for type 2 diabetes and sometimes used for prediabetes. Metformin primarily works by reducing hepatic glucose production and improving insulin sensitivity through AMPK activation. The Diabetes Prevention Program showed lifestyle changes (58% risk reduction) outperformed metformin (31% reduction) for preventing progression from prediabetes to diabetes.

Also known as: gut flora, microbiota

The community of trillions of microorganisms (bacteria, fungi, viruses) living in the gut. The gut microbiome influences metabolic health through short-chain fatty acid production, inflammation modulation, incretin hormone regulation, and gut barrier integrity. A diverse, fiber-fed microbiome is associated with better insulin sensitivity and metabolic function.

The 'powerhouses' of cells that produce energy (ATP) from glucose and fatty acids. Mitochondrial dysfunction is a hallmark of insulin resistance—when mitochondria don't function well, cells can't efficiently use glucose for energy. Exercise, particularly endurance and high-intensity interval training, stimulates mitochondrial biogenesis (creation of new mitochondria).

The process of creating new mitochondria within cells, stimulated by exercise (especially endurance and HIIT), fasting, and cold exposure. More and better-functioning mitochondria improve the cell's ability to use glucose and fatty acids for energy, directly improving insulin sensitivity and metabolic flexibility.

A nutrient-sensing protein that promotes cell growth when nutrients are abundant and is suppressed during fasting. mTOR inhibition during fasting allows autophagy (cellular cleanup) to occur. Chronic mTOR activation from constant eating and excess protein/sugar may accelerate aging and impair metabolic health. Periodic fasting helps balance mTOR activity.

The total weight of skeletal muscle in the body. Muscle is the largest organ of glucose disposal, responsible for approximately 80% of insulin-mediated glucose uptake. Maintaining and building muscle mass through resistance training is one of the most important strategies for long-term insulin sensitivity and metabolic health, especially with aging when muscle naturally declines.

Also known as: fatty liver, hepatic steatosis, MASLD

Accumulation of excess fat in the liver not caused by alcohol consumption, strongly associated with insulin resistance and metabolic syndrome. The liver becomes less responsive to insulin, continuing to produce glucose even when blood sugar is already elevated. NAFLD affects roughly 25% of the global population and is reversible through lifestyle changes, particularly reduced sugar/fructose intake and exercise.

Also known as: non-exercise activity thermogenesis

The energy expended through daily activities that are not deliberate exercise—walking, standing, fidgeting, household chores, taking stairs. NEAT can vary by 2,000+ calories per day between individuals and is a major contributor to total daily energy expenditure. Increasing NEAT through more daily movement supports metabolic health beyond structured exercise.

Also known as: n-3 fatty acids

Essential polyunsaturated fats that the body cannot produce, with potent anti-inflammatory properties. Include EPA (anti-inflammatory) and DHA (structural, brain health). Found in fatty fish (salmon, sardines, mackerel), walnuts, and flaxseed. Omega-3s reduce inflammation—a driver of insulin resistance—and improve triglyceride levels and cardiovascular health.

Also known as: glucose tolerance test, GTT

A diagnostic test where blood sugar is measured before and 2 hours after drinking a 75g glucose solution. A 2-hour value of 140-199 mg/dL indicates prediabetes; 200+ indicates diabetes. The OGTT can detect impaired glucose tolerance that fasting glucose alone may miss.

An imbalance between free radical production and the body's antioxidant defenses. Blood sugar spikes and glucose variability generate oxidative stress that damages blood vessels, proteins, and DNA. Chronic oxidative stress contributes to insulin resistance and diabetic complications. Managed through stable blood sugar, antioxidant-rich foods, exercise, and adequate sleep.

The 'rest and digest' branch of the autonomic nervous system that promotes relaxation, digestion, and recovery. Activating the parasympathetic system through deep breathing, meditation, or vagus nerve stimulation lowers cortisol, reduces blood pressure, and improves glucose metabolism. Chronic stress shifts the balance away from parasympathetic toward sympathetic (fight-or-flight) dominance.

Plant compounds with antioxidant and anti-inflammatory properties found in berries, dark chocolate, green tea, coffee, red wine, olive oil, and colorful vegetables. Polyphenols improve insulin sensitivity, support gut microbiome diversity, reduce inflammation, and may improve endothelial function. Many metabolic benefits of the Mediterranean diet are attributed to polyphenols.

The practice of walking for 10-15 minutes within 30-60 minutes after eating, when blood sugar is peaking. Muscle contractions during walking activate GLUT4 transporters to clear glucose from the blood independently of insulin. Research shows post-meal walks can reduce glucose spikes by 20-30%. One of the simplest and most effective metabolic health interventions.

Also known as: post-meal glucose, PPG

Blood sugar measured after eating, typically 1-2 hours after a meal. Even when fasting glucose is normal, high postprandial spikes can indicate early insulin resistance and contribute to oxidative stress, inflammation, and vascular damage. A target of below 140 mg/dL at 2 hours post-meal is generally recommended.

Non-digestible fibers that feed beneficial gut bacteria, supporting the production of short-chain fatty acids that improve insulin sensitivity and gut barrier function. Found in garlic, onions, leeks, asparagus, bananas, oats, and apples. Prebiotics work synergistically with probiotics to support metabolic health.

Also known as: impaired glucose tolerance, impaired fasting glucose

A metabolic condition where blood sugar levels are higher than normal but not yet high enough for a type 2 diabetes diagnosis. Diagnosed by fasting glucose 100-125 mg/dL, A1C 5.7-6.4%, or OGTT 140-199 mg/dL. About 98 million Americans have prediabetes, and without intervention, 15-30% develop type 2 diabetes within 5 years. Prediabetes is reversible through lifestyle changes.

Live beneficial bacteria that, when consumed, support the gut microbiome. Found in fermented foods (yogurt, kefir, sauerkraut, kimchi, kombucha) and supplements. Different strains have different effects on metabolic health, with some specifically shown to improve insulin sensitivity and reduce inflammation. Diversity of strains is generally more beneficial than high doses of one strain.

A macronutrient composed of amino acids, essential for muscle maintenance, enzyme production, and immune function. Protein has a moderate effect on blood sugar and stimulates both insulin and glucagon. Including protein with meals slows gastric emptying and glucose absorption, reducing postprandial blood sugar spikes. Adequate protein intake supports muscle mass, which is key for glucose disposal.

Also known as: postprandial hypoglycemia

A drop in blood sugar that occurs 2-5 hours after eating, typically following a high-carbohydrate meal that triggers an excessive insulin response. Symptoms include shakiness, sweating, anxiety, and brain fog. Common in early insulin resistance when insulin regulation is dysregulated. Managed by balancing meals with protein, fat, and fiber.

Also known as: strength training, weight training

Exercise involving working muscles against resistance (weights, bands, bodyweight) to build strength and muscle mass. Critical for metabolic health because skeletal muscle is the primary site of insulin-mediated glucose disposal, accounting for roughly 80% of glucose uptake after meals. More muscle mass literally increases the body's glucose disposal capacity.

Age-related loss of muscle mass and strength that accelerates after age 40-50. Since muscle is the primary site of glucose disposal, sarcopenia directly contributes to declining insulin sensitivity with age. Resistance training and adequate protein intake (1.2-1.6g per kg of body weight) are key prevention strategies.

Extended periods of sitting or lying down with minimal energy expenditure. Prolonged sitting impairs insulin sensitivity independently of exercise—meaning you can exercise daily but still suffer metabolic consequences from sitting 8+ hours. Regular movement breaks throughout the day are important in addition to dedicated exercise sessions.

Metabolites produced when beneficial gut bacteria ferment dietary fiber—primarily butyrate, propionate, and acetate. Butyrate is the primary fuel source for colon cells and strengthens the gut barrier. SCFAs reduce systemic inflammation, improve insulin sensitivity in muscle and liver, help regulate appetite, and support immune function.

The structure and pattern of sleep cycles throughout the night, including light sleep (N1, N2), deep sleep (N3/slow-wave sleep), and REM sleep. Adequate deep sleep is critical for metabolic health—growth hormone is released during deep sleep, and glucose metabolism is regulated during specific sleep stages. Poor sleep architecture impairs metabolic function even if total sleep time appears adequate.

The cumulative effect of not getting enough sleep over time. Sleep debt cannot be fully 'repaid' on weekends—metabolic damage from chronic sleep restriction accumulates. Even a few nights of 5-6 hours of sleep significantly impairs insulin sensitivity and glucose tolerance. Consistent 7-9 hours nightly is the foundation of metabolic health.

Practices and environmental factors that promote quality sleep: consistent sleep/wake times (within 30-60 minutes daily), dark and cool bedroom (65-68F), no screens 1-2 hours before bed, limiting caffeine after noon, avoiding large meals close to bedtime, and a calming pre-sleep routine. These practices support circadian-driven metabolic processes including insulin secretion and glucose metabolism.

The discrepancy between sleep timing on workdays versus free days (e.g., sleeping late on weekends). This misalignment disrupts circadian rhythm and is associated with impaired glucose tolerance, higher BMI, and increased metabolic risk—even without reducing total sleep hours. Keeping sleep timing consistent within 30-60 minutes daily supports metabolic health.

Fat stored directly under the skin, throughout the body. While excess subcutaneous fat can be a health concern, it is less metabolically harmful than visceral fat because it doesn't release the same inflammatory signals. Two people with the same BMI can have very different health profiles depending on how much of their fat is visceral versus subcutaneous.

The 'fight or flight' branch of the autonomic nervous system that prepares the body for action by raising heart rate, blood pressure, and blood sugar. While essential for acute stress response, chronic sympathetic activation (from ongoing stress, poor sleep, or overexercise) promotes insulin resistance and metabolic dysfunction.

Also known as: TRE, time-restricted feeding

A form of intermittent fasting that limits the daily eating window, typically to 8-12 hours, and extends the overnight fast. TRE aligns eating with circadian rhythm and allows insulin levels to drop during the fasting period, improving insulin sensitivity. Research shows metabolic benefits even without calorie reduction. The 16:8 pattern (16 hours fasting, 8 hours eating) is most commonly studied.

A simple calculation from a standard lipid panel (triglycerides divided by HDL cholesterol) that strongly correlates with insulin resistance and cardiovascular risk. A ratio below 2.0 is ideal; above 3.0 suggests significant insulin resistance. Many people with 'normal' total cholesterol have an elevated TG:HDL ratio, revealing hidden metabolic dysfunction.

A type of fat in the blood, measured as part of a lipid panel. Elevated triglycerides (above 150 mg/dL) are a component of metabolic syndrome and strongly associated with insulin resistance. High triglycerides often result from excess carbohydrate intake (the liver converts excess carbs to triglycerides), excess alcohol, and insulin resistance. Ideally below 100 mg/dL.

Also known as: T2D, type 2 diabetes mellitus, T2DM

A chronic metabolic disease characterized by sustained high blood sugar due to insulin resistance and eventual beta cell dysfunction. Diagnosed by fasting glucose of 126+ mg/dL, A1C of 6.5%+, or OGTT of 200+ mg/dL. It develops gradually and is strongly influenced by lifestyle factors including diet, exercise, sleep, and stress.

Industrial formulations containing many ingredients including additives, preservatives, emulsifiers, and artificial flavors, typically made from extracted or refined substances rather than whole foods. Associated with insulin resistance, obesity, inflammation, and gut microbiome disruption. Examples include most packaged snacks, fast food, sugary drinks, and processed meats.

A waste product from purine metabolism that, when elevated (hyperuricemia), is associated with gout, kidney stones, insulin resistance, and cardiovascular disease. Fructose consumption is a major driver of elevated uric acid. Elevated uric acid can both result from and contribute to metabolic dysfunction, making it a useful metabolic health marker.

The longest cranial nerve, connecting the brain to the gut, heart, and other organs. It is the primary pathway of the parasympathetic nervous system. Vagal tone (vagus nerve activity) affects digestion, heart rate, inflammation, and mood. Stimulating the vagus nerve through deep breathing, cold exposure, singing, or gargling activates the relaxation response and can improve metabolic function.

Also known as: intra-abdominal fat, central adiposity

Fat stored within the abdominal cavity around internal organs (liver, pancreas, intestines). Unlike subcutaneous fat (under the skin), visceral fat is metabolically active, releasing inflammatory cytokines and hormones that directly drive insulin resistance, raise triglycerides, and increase cardiovascular risk. Waist circumference is a better indicator of visceral fat than BMI.

A fat-soluble vitamin synthesized through sun exposure and obtained from fatty fish, fortified foods, and supplements. Vitamin D receptors are present on pancreatic beta cells, and deficiency is associated with increased insulin resistance and higher type 2 diabetes risk. Many people are deficient, especially those with limited sun exposure.

The maximum rate of oxygen consumption during exercise, considered the gold standard measure of cardiovascular fitness. Higher VO2 max is strongly associated with better insulin sensitivity, lower diabetes risk, and reduced all-cause mortality. It can be improved at any age through regular aerobic exercise.

A measurement taken around the natural waistline (above the hip bones) that serves as a proxy for visceral fat. Elevated waist circumference (above 40 inches for men, 35 inches for women) is a component of metabolic syndrome and a stronger predictor of metabolic and cardiovascular risk than BMI alone.