BODY COMPOSITION
BMI (Body Mass Index)
A weight-to-height screening ratio used in population charts. It does not measure muscle, visceral fat, fitness, or disease. Two adults can share a BMI and not share a body or a risk story.
FORMULA
BMI = weight (kg) ÷ [height (m)]² · US form: BMI ≈ 703 × lb ÷ in²EXAMPLE
175 cm / 70 kg → BMI ≈ 22.9 (common adult “normal” band 18.5–24.9). Corridor edges for that height are about 56.7–76.3 kg.
WHY IT MATTERS
BMI is a fast map pin before deeper metrics (waist, labs, training context). It is a starting chart, not a diagnosis.
COMMON MISTAKES
- Treating BMI as a health verdict or moral score
- Ignoring height-squared sensitivity and memory height
- Using adult bands for children, teens, or pregnancy
BODY COMPOSITION
Ideal body weight (IBW)
Formula-based weight ranges by height (and sometimes sex), such as Devine, Robinson, Miller, or Hamwi. Different equations disagree. None is a personal goal prescription.
EXAMPLE
At the same height, Devine and Hamwi can differ by several kilograms. Treat the spread as a chorus, not a single target.
WHY IT MATTERS
IBW sketches are literacy for charts and some clinical dosing contexts. Your goal weight still needs clinician and lifestyle context.
COMMON MISTAKES
- Picking one IBW formula and treating it as destiny
- Confusing IBW with body-composition goals
BODY COMPOSITION
Body fat percentage
Estimated share of total mass that is fat tissue. Skinfold, Navy circumference, DEXA, and consumer scales use different methods and error bands.
EXAMPLE
Two people at BMI 28 can show very different fat vs lean splits. Composition explains why the same BMI looks different on a trained athlete.
WHY IT MATTERS
Composition adds signal BMI cannot provide. Still treat consumer estimates as sketches, not lab truth.
COMMON MISTAKES
- Treating handheld or smart-scale readings as DEXA accuracy
- Comparing methods that use different formulas week to week
ENERGY & NUTRITION
BMR (Basal Metabolic Rate)
Estimated calories burned at complete rest to maintain vital functions. Common equations include Mifflin-St Jeor and Harris-Benedict. They disagree by a meaningful delta for the same person.
EXAMPLE
A 30-year-old, 70 kg, 175 cm male might show BMR near 1,650–1,750 kcal/day depending on the equation.
WHY IT MATTERS
BMR is the floor under TDEE. Long-term intakes far below BMR are usually unsustainable and can backfire.
COMMON MISTAKES
- Confusing BMR with total daily burn
- Using BMR alone as a diet calorie target
ENERGY & NUTRITION
TDEE (Total Daily Energy Expenditure)
Estimated calories burned in a full day: BMR plus activity, exercise, digestion (TEF), and non-exercise movement (NEAT). Often sketched as BMR × activity multiplier.
FORMULA
TDEE ≈ BMR × activity multiplierEXAMPLE
BMR 1,700 kcal × 1.55 (moderately active) ≈ 2,635 kcal/day maintenance sketch.
WHY IT MATTERS
Weight change follows energy balance versus TDEE over weeks, not single-day scale noise.
COMMON MISTAKES
- Overstating activity level on the multiplier
- Expecting the scale to move in 2–3 days
ENERGY & NUTRITION
Calorie (kcal)
The unit used for food energy on labels. Consumer “calories” are kilocalories (kcal). Goal calorie tools sketch intake relative to TDEE for loss, maintain, or gain.
EXAMPLE
A mild loss pace might target about 0.5% of body weight per week, translated into a daily calorie budget above a BMR floor.
WHY IT MATTERS
Macro and calorie targets only work if portions and logging are consistent enough to learn from.
COMMON MISTAKES
- Crash deficits that ignore the BMR floor
- Treating burn estimates as exact banked calories
ENERGY & NUTRITION
Calories burned (activity)
Estimated energy cost of an activity from MET values, body weight, and duration. Gross burn includes resting metabolism during the session; net burn tries to isolate the activity increment.
WHY IT MATTERS
Useful for comparing sessions, not for “earning” food with perfect precision. Wearables and MET tables both have error.
COMMON MISTAKES
- Double-counting workout burn on top of an already-active TDEE multiplier
- Equating gross device burn with fat loss
ENERGY & NUTRITION
Macronutrients (macros)
Protein, carbohydrates, and fat: the nutrients that provide calories and structure a diet split. Fiber and alcohol also affect energy accounting.
EXAMPLE
2,000 kcal at 30% protein / 40% carbs / 30% fat ≈ 150 g protein, 200 g carbs, 67 g fat.
WHY IT MATTERS
Protein supports lean mass and satiety; carbs fuel training; fats carry fat-soluble vitamins. Balance depends on goals and tolerance.
COMMON MISTAKES
- Chasing ratios without hitting total calories
- Under-eating protein while dieting
ENERGY & NUTRITION
Protein intake
Dietary protein supports muscle repair, satiety, and enzyme function. Needs often rise with training and during a calorie deficit.
EXAMPLE
75 kg person at 1.6 g/kg/day → about 120 g protein daily (planning sketch, not medical advice).
WHY IT MATTERS
Adequate protein helps preserve muscle in a deficit, especially with resistance training.
COMMON MISTAKES
- Anchoring protein only as a calorie percentage with no gram floor
- Ignoring kidney or clinical constraints without clinician guidance
ENERGY & NUTRITION
Intermittent fasting (IF)
An eating-window protocol (for example 16:8 or 14:10) that schedules when you eat, not magically what energy balance does. Weight change still follows calories over time.
EXAMPLE
16:8 with a noon–8 PM window means overnight and morning hours are fasted; total daily calories still decide the trajectory.
WHY IT MATTERS
IF can help some people control intake timing. It is not a substitute for nutrient needs, medical constraints, or pregnancy guidance.
COMMON MISTAKES
- Assuming the window alone creates fat loss without a deficit
- Using aggressive fasts with eating-disorder history or without medical clearance
The heaviest load you can lift once with good form for a given lift. Often estimated from submaximal sets (Epley, Brzycki, and similar).
EXAMPLE
100 kg × 5 reps → Epley-style estimate ≈ 116.7 kg; Brzycki ≈ 112.5 kg. Formulas diverge as reps rise.
WHY IT MATTERS
1RM estimates program intensity (% of max) without testing a true max every week.
COMMON MISTAKES
- Using 1RM formulas on high-rep sets (10+)
- Skipping warm-up before true max tests
Time per distance (min/mile or min/km). Pace, speed, and finish time convert each other for race and long-run planning.
EXAMPLE
8:00 min/mile ≈ 7.5 mph; a 10K at that pace ≈ 49:40.
WHY IT MATTERS
Even pacing prevents blowing up early in races and long runs. Convert units carefully (mile vs km).
COMMON MISTAKES
- Mixing mile and kilometer pace without converting
- Ignoring elevation and heat when predicting finish time
CARDIO
Target heart rate zones
Training ranges based on estimated or measured maximum heart rate. Zones map roughly to easy, aerobic, and hard efforts. Age formulas are population sketches.
FORMULA
Common estimate: max HR ≈ 220 - age (population rule of thumb)EXAMPLE
Age 40 → estimated max ~180 bpm; a moderate band might sit near 60–80% of that estimate.
WHY IT MATTERS
Zones help pace cardio without making every session all-out. Medications and fitness change the picture.
COMMON MISTAKES
- Treating 220 - age as exact personal physiology
- Ignoring medications that affect heart rate
CARDIO
Resting heart rate (RHR)
Heartbeats per minute at true rest, usually measured seated or lying after quiet time. Trends over days matter more than one noisy reading.
EXAMPLE
Count 30 seconds of pulse and double to get bpm. Average a few morning samples before stressing about a single day.
WHY IT MATTERS
RHR trends can reflect recovery, illness, or fitness change. It is not a diagnosis by itself.
COMMON MISTAKES
- Measuring after caffeine, stress, or a hard workout
- Treating one elevated reading as an emergency without context (seek care for concerning symptoms)
PREGNANCY
Gestational age & due date
Standard obstetric dating often counts from the first day of the last menstrual period (LMP), not the conception day. Due date is an estimate; term is a window.
EXAMPLE
LMP-based EDD is commonly LMP + 280 days. Ultrasound dating can revise the estimate later.
WHY IT MATTERS
Dating drives prenatal visit timing and trimester language. Clinical care owns final dating decisions.
COMMON MISTAKES
- Treating EDD as a guaranteed birthday
- Using adult BMI tools as pregnancy weight guidance
PREGNANCY
Ovulation window
The fertile window is typically a few days before and through ovulation. Cycle length and luteal phase vary. Calendar tools are estimates, not contraception.
WHY IT MATTERS
Timing around ovulation can improve conception odds versus guessing alone. Irregular cycles need clinical guidance.
COMMON MISTAKES
- Using ovulation apps as birth control
- Assuming every cycle is exactly 28 days
PREGNANCY
Conception date estimate
A back-dated estimate of when fertilization likely occurred, often derived from LMP, due date, or ultrasound dating. It is a planning sketch with uncertainty.
WHY IT MATTERS
Useful for personal timelines and some paperwork literacy. Clinical dating still rules medical decisions.
COMMON MISTAKES
- Treating a single calendar day as certain when sperm and egg timing span days
HABITS & WELLNESS
Daily water intake
Fluid needs depend on body size, climate, activity, and pregnancy or breastfeeding status. Urine color and thirst are practical checks beside any formula.
WHY IT MATTERS
Dehydration hurts performance and cognition. Extreme over-hydration without electrolytes can be risky.
COMMON MISTAKES
- Forcing huge fixed liters regardless of sweat and climate
- Ignoring that coffee, tea, and food water also count toward fluid
HABITS & WELLNESS
BAC (blood alcohol content)
Estimated alcohol concentration in blood from drinks, body size, sex assigned in the model, and time. Impairment rises with BAC. Legal limits and rules vary by place.
WHY IT MATTERS
Estimates support planning safe transport and understanding how pace and food change risk. They are not courtroom evidence.
COMMON MISTAKES
- Treating calculator output as legal proof of sobriety
- Assuming coffee or a cold shower instantly reverses impairment
- Driving based on a “feel sober” guess