Methodology · research note
Why nutrient density needs vary by ~3× across people
Calories scale with body mass and activity. Most micronutrient targets do not. A smaller, less-active, or older person eats fewer calories - but still needs roughly the same iron, calcium, and vitamins as everybody else. The result: their food has to be much denser per calorie. We ran this calculation across 420 profiles. Here is what falls out.
Spread
2.86×
Required density between most and least demanding profile
Lowest demand
0.69
18y man, 110kg, extremely active (4,043 kcal)
Highest demand
1.98
75y woman, 45kg, sedentary (1,134 kcal)
The whole landscape
Each dot is one profile. Lower calorie budgets sit on the left and need a higher density score on the y-axis to cover the same daily targets. The dashed line at 1.00 is the calibration anchor: a 30-year-old, 75 kg, moderately active man.
Six archetypes side-by-side
The same six daily targets cost very different amounts of density work depending on who is eating.
| Profile | Activity | Calories | Density |
|---|---|---|---|
Active young man male, 18y, 95kg · Highest calorie budget - lowest required density | very active | 3,412 | 0.80 |
Average man male, 35y, 75kg | moderately active | 2,624 | 1.02 |
Older lightly-active man male, 65y, 75kg | lightly active | 2,122 | 1.26 |
Average woman female, 35y, 62kg | moderately active | 2,038 | 1.11 |
Older lightly-active woman female, 65y, 62kg | lightly active | 1,602 | 1.45 |
Petite older sedentary woman female, 75y, 45kg · Most demanding profile in the grid | sedentary | 1,134 | 1.98 |
Which nutrients vary the most across profiles?
For each nutrient we computed the required intake per 1,000 kcal under every profile, then took the ratio of the largest to the smallest. A high ratio means the density requirement for that nutrient swings dramatically depending on who is eating. The top entry is iron.
Why iron is an outlier (6.81×)
The DRI for iron is 18 mg/day for premenopausal women versus 8 mg/day for men - a 2.25× gap that compounds with the calorie gap between, say, a young woman and a heavier active man. The result is the largest per-kcal density swing of any nutrient in the system: from 2.0 mg/1,000 kcal at the easiest profile to 13.7 mg/1,000 kcal at the hardest. Phosphorus, vitamin D, vitamin K, and calcium follow a similar pattern: their RDAs are largely fixed by age, while calories are not.
What this means for meal planning
- A “healthy average meal” calibrated for a young active man under-delivers nutrients to lower-calorie profiles. Iron, calcium, vitamin D, and vitamin K are the first to fall out of reach.
- Per-calorie density targets, not per-meal calories, are the right unit for cross-profile recommendations. Two people eating the same plate hit different fractions of their daily needs.
- Older women are the binding constraint. If a meal plan works for a sedentary 75-year-old woman on 1,200 kcal, it comfortably works for everyone above her on the calorie ladder.
- Generic “eat the rainbow” advice is insufficient. The harder profiles need targeted dense foods - liver, leafy greens, dairy, fortified cereals, oily fish - to clear daily targets without an unrealistic calorie budget.
How the numbers were computed
The score for each profile is K · Σ(positive_weight · RDA_db_unit) / calories. The constant K is chosen so the reference profile (30-year-old man, 75 kg, moderately active) lands at exactly 1.00. Higher score = profile needs more nutrient per calorie to hit its RDAs.
The grid covers 420profiles: 2 sexes, 7 age bands (18–75), 6 weights, and 5 activity levels. 27nutrients contribute to the positive side - vitamins, minerals, omega-3, plus protein and fiber from the app's calculator functions so the analysis matches what users actually see in the app. Calorie targets use the Mifflin-St Jeor equation with activity multipliers; RDAs come from the U.S. Dietary Reference Intakes.
Caveats: pregnancy and lactation rows are excluded from the grid; height is held at population-average per sex; the “extremely active” multiplier represents an upper bound that few users sustain in practice. Carotenoid forms of vitamin A are excluded from the positive side because they have no per-profile RDA in the DRI tables.
Read further
- How nutrient targets are calculated - the DRI / RDA / UL framework these numbers sit on top of.
- Foods ranked by nutrient density - the food-side companion to this profile-side analysis.
- Dietary Reference Intakes (National Academies)