Sources & methodology
Phlo shows
its work.
Understand the numbers behind your wellness.
The research, the calculations, and the choices Phlo makes.
What published research and guidance support.
How Phlo applies itThe product decisions behind Phlo’s numbers.
Calories
A starting estimate. A clear calculation.
Research says
The Mifflin–St Jeor equation estimates resting energy needs. It was developed from 498 healthy adults ages 19–78. A 2005 review found it more reliable than the other equations compared, but individual errors remain.
How Phlo applies it
For adults 19+, Phlo multiplies that resting estimate by a Phlo activity factor to estimate maintenance calories. The resting equation comes from research; the activity mapping is Phlo’s decision.
Maintenance = resting estimate × activity factor
See the adult formulas & sources
Mifflin–St Jeor resting metabolic rate (RMR)
Weight in kilograms, height in centimeters, age in years. Results are in kcal/day.
Male equation10 × weight + 6.25 × height − 5 × age + 5
Female equation10 × weight + 6.25 × height − 5 × age − 161
The 2005 review compared Mifflin–St Jeor, Harris–Benedict, Owen and WHO/FAO/UNU. Mifflin predicted within 10% of measured RMR for more individuals; that is not a promise of 10% accuracy for every person.
The combined maintenance calculation is Phlo methodology, not a formula validated as a whole by the original Mifflin study. Ages 13–18 follow a separate approach.
Activity & Steps
Steps are one part of the picture.
Research says
Tudor-Locke and Bassett proposed adult step classifications, from under 5,000 steps a day to highly active levels above 12,500. These are preliminary public-health indices, not precise measures of calorie expenditure.
How Phlo applies it
Phlo groups the step ranges into four activity levels. Its multipliers and initial step goals are product choices, not values prescribed by Tudor-Locke.
Compare step ranges, Phlo factors & starting goals
How Phlo applies the evidence · adults 19+
| Phlo level | Steps/day | Factor | Initial goal |
|---|---|---|---|
| Mostly sitting | Under 5,000 | 1.20 | 2,500 |
| Somewhat active | 5,000–7,499 | 1.375 | 5,000 |
| Active day-to-day | 7,500–9,999 | 1.55 | 7,500 |
| Very active | 10,000+ | 1.725 | 10,000 |
The original research classifications
Under 5,000: sedentary lifestyle index; 5,000–7,499: low active; 7,500–9,999: somewhat active; 10,000 or more: active; above 12,500: highly active. Phlo’s labels differ from those research labels.
Cycling, swimming, strength training and physical labor can provide meaningful activity evidence even when steps are low. See the planned adjustment methodology.
Lose / Maintain / Gain
A selected pace is an estimate, never a promise.
Research says
CDC describes about 1–2 lb/week as a gradual weight-loss pace. Adult guidelines support calorie deficits, but a fixed deficit does not produce an exact weekly scale change.
Evidence for gain-rate settings is weaker. A 2022 review describes roughly 300–500 additional kcal/day as a common starting recommendation.
How Phlo applies it
Phlo’s adult settings use maintenance calories, then subtract or add 500 or 1,000 kcal/day for the selected rate. Actual changes in weight and body composition vary.
The evidence does not strongly validate +1,000 kcal/day as a reliable 2 lb/week gain prescription.
See all rate settings, guardrails & sources
| Selected setting | Daily calorie calculation |
|---|---|
| Lose ~1 lb/week | Maintenance − 500 kcal |
| Lose ~2 lb/week | Maintenance − 1,000 kcal |
| Maintain | Maintenance estimate |
| Gain ~1 lb/week | Maintenance + 500 kcal |
| Gain ~2 lb/week | Maintenance + 1,000 kcal |
Major adult guidelines describe calorie-restricted ranges of 1,200–1,500 kcal/day for women and 1,500–1,800 for men, and calculated deficits such as 500–750 kcal/day. These ranges inform Phlo’s hard blocks; they do not establish the exact product rules or guarantee that a given intake is appropriate for everyone.
The gain review focuses on athletes and military personnel; it does not establish a precise gain rate for all users, particularly as lean mass. Adult offsets and floors are not automatically applied to ages 13–18.
Macros
A simple default within established adult ranges.
Research says
The National Academies’ adult Acceptable Macronutrient Distribution Ranges are 45–65% carbohydrate, 10–35% protein and 20–35% fat.
Standard general energy factors are 4 kcal/g for carbohydrate and protein, and 9 kcal/g for fat.
How Phlo applies it
Phlo chose this general-wellness default. The National Academies supports the ranges, not this exact split.
See the calorie-to-gram formulas & sources
Carbohydrate gramsCalorie goal × 0.50 ÷ 4
Protein gramsCalorie goal × 0.20 ÷ 4
Fat gramsCalorie goal × 0.30 ÷ 9
The ranges above are adult reference ranges. They are not a personalized prescription or proof that one ratio is best for everyone.
Water
A practical starting goal, with room for real life.
Research says
UC Irvine and Military Health System guidance describe half your body weight in ounces as a practical hydration starting point. Needs vary with activity, heat, illness and individual circumstances.
Hydration includes fluid from more than plain water; the military guidance also recognizes other beverages.
How Phlo applies it
Phlo’s Water metric counts plain water only. That tracking boundary is a Phlo product choice, not a claim that other drinks do not hydrate.
Daily Water goal (fl oz) = weight (lb) × 0.5
Read the hydration limits & sources
The National Academies did not establish a universal Tolerable Upper Intake Level for water. It discusses acute toxicity when rapid intake greatly exceeds the kidneys’ approximate maximum excretion rate of 0.7–1.0 L/hour. This is not an individual safe-drinking limit.
Cleveland Clinic advises that more than about 32 oz / 1 liter per hour is probably too much. Phlo’s approximate warning should be read in that practical context.
Phlo does not impose a universal daily maximum for healthy adults. The weight-based starting goal is not a universal clinical requirement; individual fluid needs and clinician-directed restrictions can differ.
Ages 13–18
Growing bodies need a different approach.
Research says
Mifflin’s original study involved adults ages 19–78. The National Academies’ 2023 youth Estimated Energy Requirement methodology accounts for age, activity and energy for growth.
NIDDK advises working with a health professional on a child’s or teen’s weight-management needs. Some young people may need to gain weight more slowly as they grow, rather than lose it.
How Phlo applies it
Phlo does not apply its adult Mifflin weight-change system to teenagers. Where it uses a teen energy reference, the scientific basis is the National Academies’ growth-aware youth methodology.
No automatic adult calorie deficits, surpluses, calorie floors or calculated goal weight.
See the youth boundaries & sources
- No adult Mifflin calculation for ages 13–18.
- No automatic −500 / −1,000 kcal deficits or +500 / +1,000 kcal surpluses.
- No adult 1,200 / 1,500 calorie-floor logic.
- No automatically calculated goal weight.
Youth activity context
HHS guidance for ages 6–17 is at least 60 minutes of moderate-to-vigorous physical activity each day. That age range differs from Phlo’s 13–18 energy-methodology boundary. Phlo does not translate the 60-minute guidance into a specific step count or calorie deduction without separately validating such a method.
How Phlo adjusts goals
Look for sustained patterns. Keep your choices yours.
Planned methodology The source pack describes the activity-review rules below as planned. They are documented here as intended behavior, not a claim that every rule is available in the current app.
Research says
HHS recommends 150–300 minutes of moderate aerobic activity a week, plus muscle-strengthening activity on at least two days. CDC uses a rough equivalence of one vigorous minute to two moderate minutes.
This supports considering activity beyond steps. It does not prescribe Phlo’s review windows or category-change rules.
How Phlo applies it
The planned approach reviews sustained patterns, with AI Goal Adjustments on by default and manual overrides taking precedence.
Your chosen goal weight and rate remain yours. Phlo does not infer an “ideal” weight or generate one from BMI.
See the planned review rules & sources
- Review a rolling 28 days. Require at least 14 valid step days.
- Look for sustained support. A new category should be supported for about 21 of the last 28 days before the activity factor changes.
- Move one category at a time. Include meaningful non-step activity such as cycling, swimming, strength training and physical labor.
- Respect user choices. Manual overrides win; the selected goal weight and rate remain user choices.
- Avoid counting activity twice. No extra workout-calorie “eat back” on top of activity-adjusted maintenance calories.
These thresholds and defaults are Phlo methodology decisions. The source pack does not define the precise criteria for a “valid step day”; that definition remains to be confirmed before presenting the review rules as fully specified, live behavior.
Source organizations do not endorse Phlo by being listed here. Phlo is for general wellness, not medical diagnosis or treatment. Estimates and defaults are starting points, not individualized clinical advice.