A–Z Glossary of Weight-Loss Terms

A clear, clinic-friendly guide to the words you’ll see in weight management programs, nutrition labels, and doctor visits.

A

Adipose tissue (fat)
Body fat stored under the skin (subcutaneous) and around organs (visceral). Excess visceral fat is linked to insulin resistance and cardiometabolic risk.

Adequate protein
Protein intake high enough to preserve lean mass during weight loss (often ~1.2–1.6 g/kg/day, individualized).

Appetite suppressant
A medication or strategy that reduces hunger and cravings (e.g., phentermine, GLP-1/GIP agents when appropriate).

B

Bariatric (obesity) surgery
Operations on the stomach/intestine (e.g., sleeve gastrectomy, gastric bypass) for severe obesity (typically BMI ≥40, or ≥35 with comorbidities). Requires lifelong nutrition follow-up.

Basal Metabolic Rate (BMR)
Calories your body uses at complete rest; largest part of daily energy use.

Bioelectrical Impedance Analysis (BIA)
A quick, noninvasive estimate of body composition using a small electrical current.

Body composition
Proportions of fat mass and fat-free mass (muscle, bone, organs, water).

Body Mass Index (BMI)
Weight(kg)/height(m)². General categories for adults:

• 18.5–24.9 healthy, 25.0–29.9 overweight, ≥30 obese (screening tool; doesn’t directly measure fat).

C

Calorie
Unit of energy in food. Protein & carbs = 4 kcal/g; fat = 9 kcal/g; alcohol = 7 kcal/g.

Calorie deficit
Eating fewer calories than you burn; needed for fat loss.

Carbohydrate
Major energy source. Simple (sugars) and complex (starches, fiber).

Cholesterol
Waxy substance made by the body and found in animal foods. Carried in blood by LDL (“bad”) and HDL (“good”) lipoproteins.

Continuous Glucose Monitor (CGM)
Wearable sensor tracking glucose; sometimes used to guide nutrition choices.

D

Diabetes mellitus
High blood glucose from lack of insulin (Type 1) or insulin resistance/relative deficiency (Type 2).

Diet
Your habitual eating pattern; may be structured for weight or health.

Dietary fiber
Indigestible carbs that improve fullness, gut health, and glucose control (aim 25–35 g/day).

E

Energy density
Calories per gram of food. Lower energy-density foods (vegetables, broth-based soups) allow larger portions for fewer calories.

Energy expenditure
Calories you burn via basal metabolism, activity, and digestion.

Evidence-based
Supported by high-quality research; preferred for safe, effective weight care.

F

Fat (dietary)
Provides 9 kcal/g. Types: saturated, trans, monounsaturated, polyunsaturated (omega-3/omega-6). Helps absorb vitamins A, D, E, K.

Fatty liver (NAFLD/MASLD)
Excess fat in the liver, often tied to insulin resistance and central obesity.

Fad diet
Trendy plan promising fast results without science; typically unsustainable.

G

Gastrointestinal (metabolic) surgery
See Bariatric surgery.

Gestational diabetes
Diabetes first recognized in pregnancy; increases later risk of Type 2 diabetes.

Glycemic index (GI)/Glycemic load (GL)
GI: how fast a carb food raises blood sugar; GL: GI plus portion size impact.

Glucose
Primary sugar in blood; main energy source for cells.

GLP-1 / GIP medications
Injectables that enhance satiety and support weight loss (e.g., semaglutide, tirzepatide) when appropriate.

H

HDL (High-Density Lipoprotein)
“Good” cholesterol carrier that helps remove cholesterol from the bloodstream.

Healthy weight
Weight range associated with lower disease risk; often corresponds to BMI 18.5–24.9 but should be considered with body composition and health markers.

Hypertension (high blood pressure)
Persistent BP ≥140/90 mmHg (diagnostic thresholds may vary by guideline); raises cardiovascular risk.

Hyperinsulinemia
Chronically high insulin levels, commonly with insulin resistance.

Hydrogenation / Trans fats
Process turning liquid oils solid; creates trans fats that increase heart disease risk.

I

Ideal body weight (IBW)
Legacy estimate of “target” weight; less useful than individualized, health-based goals.

Insulin
Pancreatic hormone that helps glucose enter cells; high levels promote storage.

Insulin resistance
Cells respond poorly to insulin, raising blood glucose and insulin levels; central to metabolic syndrome.

Intensive Behavioral Therapy (IBT)
Structured coaching to change eating/activity/sleep habits for durable weight control.

J

Joint loading
Force on joints from body weight; weight loss can reduce knee/hip pain.

K

Ketogenic diet (“keto”)
Very low-carb, higher-fat diet that can reduce appetite and improve glycemia for some; requires planning and medical guidance for certain conditions.

Kilocalorie (kcal)
Same as “calorie” on food labels.

L

LDL (Low-Density Lipoprotein)
“Bad” cholesterol carrier; higher levels increase cardiovascular risk.

Lean body mass (LBM)
Everything minus fat mass; crucial to preserve during weight loss.

Low-Calorie Diet (LCD)
Typically ~1,000–1,500 kcal/day; often physician-guided.

M

Maintenance calories
Calories at which weight is stable (a moving target as weight/activity change).

Meal replacement
Portion-controlled shakes/bars/soups used to create a calorie deficit with adequate protein/micronutrients.

Metabolic adaptation
Decrease in energy expenditure with weight loss beyond what size changes predict.

Metabolism
All processes that convert food to usable energy.

Monounsaturated fat
Found in olive/avocado oils, nuts, seeds; heart-friendly when replacing saturated fat.

Metabolic syndrome
Cluster (abdominal obesity, high BP, high triglycerides, low HDL, elevated glucose) raising diabetes/heart disease risk.

N

NEAT (Non-Exercise Activity Thermogenesis)
Calories burned by everyday movement (walking, chores, fidgeting); big driver of daily burn.

Nutrition
How the body uses food; also the science of food and health.

Non-alcoholic fatty liver disease
See Fatty liver.

O

Obesity
Excess body fat (commonly BMI ≥30) with increased health risk.

Obesogenic environment
Settings that promote overeating and inactivity (ubiquitous snacks, large portions, sedentary work).

Overweight
BMI 25.0–29.9 (screening category).

P

Pancreas
Gland that makes digestive enzymes and hormones including insulin.

Plate method
Visual guide: ½ non-starchy veggies, ¼ protein, ¼ smart carbs; add healthy fats.

Polyunsaturated fat
Includes omega-3 and omega-6 fats; liquid at room temp; found in fish, nuts, seeds, certain oils.

Portion size
Amount of food you actually eat (often larger than the serving size on labels).

Protein
Builds/repairs tissues; 4 kcal/g; key for satiety and muscle preservation during weight loss.

Q

Quality of calories
Protein- and fiber-rich whole foods aid fullness and health beyond the raw calorie number.

R

Resting Metabolic Rate (RMR)
Calories burned at rest; measured (indirect calorimetry) or estimated (formulas like Mifflin-St Jeor).

Resistance (strength) training
Exercise to preserve/build muscle; supports metabolism and long-term weight maintenance.

S

Saturated fat
Solid at room temp; high intakes can raise LDL cholesterol.

Satiety
Fullness/satisfaction after eating; enhanced by protein, fiber, and volume.

Set point
A hypothesized weight range the body defends; habits and sustained behaviors can shift it over time.

Sleep apnea (OSA)
Breathing pauses during sleep; common in obesity and can hinder weight loss; treatable.

Sodium
Excess raises blood pressure; common in processed foods.

T

TEF (Thermic Effect of Food)
Energy used to digest/absorb food (~10% of daily burn; higher for protein).

Total daily energy expenditure (TDEE)
All calories burned in a day (RMR + activity + TEF).

Trans fatty acids
Formed via hydrogenation; increase heart disease risk; avoid.

Type 1 diabetes
Autoimmune insulin deficiency; requires insulin therapy.

Type 2 diabetes
Insulin resistance with relative insulin deficiency; managed with lifestyle and medications.

U

Ultra-processed foods (UPFs)
Industrial formulations high in refined grains, sugars, fats, and additives; often energy-dense and less satiating.

Unsaturated fats
Mono- and polyunsaturated fats; generally heart-healthy when replacing saturated fats.

V

Very-Low-Calorie Diet (VLCD)
~800 kcal/day or less; doctor-supervised with medical monitoring; often uses meal replacements.

Visceral fat
Fat around abdominal organs; more metabolically harmful than subcutaneous fat.

VO₂ max
Maximal oxygen uptake; indicator of cardiorespiratory fitness.

W

Waist circumference / Waist-to-height ratio
Central fat markers linked to risk. Common cutoffs: >35″ (women) and >40″ (men) indicate higher risk; WHtR goal often <0.5.

Weight management
Achieving and maintaining a healthier weight with nutrition, activity, sleep, and behavior strategies.

Weight cycling (“yo-yo” dieting)
Repeated loss/regain; reduced by sustainable plans and maintenance skills.

X

Xerostomia
Dry mouth—can occur with some weight-loss medications or dehydration; may affect hunger, taste, and food choices.

Y

Yield (food prep)
How much cooked food you get from raw ingredients; helps accurate calorie logging.

Z

Zzz (sleep)
7–9 hours nightly supports appetite hormones, recovery, and weight-loss success.

Related clinical ranges & tools (quick reference)

• BMI: healthy 18.5–24.9; overweight 25.0–29.9; obese ≥30

• HDL: ≥60 mg/dL protective; <40 mg/dL low

• LDL: lower is generally better; individualized targets

• Blood pressure: aim <120/80 mmHg (individualized)

Need help applying these terms to your plan?

W8MD Medical Weight Loss & Sleep – Northeast Philadelphia (Primary)
1718 Welsh Road, 2nd Floor, Ste C, Philadelphia, PA 19115 • (215) 676-2334
NYC: 2632 East 21st Street, Ste L3, Brooklyn, NY 11235 • (718) 946-5500

Educational only; not a substitute for medical advice. Your W8MD clinician can tailor targets, labs, and therapies to your health profile.