Resting energy and maintenance calories
MassMetrics estimates resting energy with the Mifflin–St Jeor equation [1]. Weight is in kilograms, height in centimeters, and age in years:
Male: 10 × weight + 6.25 × height − 5 × age + 5
Female: 10 × weight + 6.25 × height − 5 × age − 161
Unspecified: 10 × weight + 6.25 × height − 5 × age − 78
The male and female constants are from the published equation. The −78 midpoint constant for “unspecified” is a MassMetrics product assumption, not a separately validated Mifflin–St Jeor equation. Even published equations have meaningful individual prediction error [2].
Estimated maintenance calories equal resting energy multiplied by the selected activity factor:
- Mostly seated
- × 1.2
- Lightly active
- × 1.375
- Active
- × 1.55
- Very active
- × 1.725
These exact activity categories and coefficients are conventional calculator assumptions—not one uniquely validated scientific scale. Real needs depend on age, body size, sex, activity, and other individual factors [3].
Weight-change targets
Initial weight-change math approximates 7,700 kcal per kilogram. This is a static planning shortcut. It does not model metabolic adaptation or changing energy expenditure and can overpredict long-term weight change [5].
For weight loss
The initial calorie reduction is capped by all three of: the requested pace, 25% of estimated maintenance, and nominal daily calorie floors of 1,200 using the female equation, 1,500 using the male equation, or 1,350 when unspecified. If maintenance is below the applicable nominal floor, MassMetrics limits the initial deficit to 10%.
This exact composite rule is a MassMetrics guardrail; the full rule has not itself been clinically validated.
For weight gain
The calorie increase is capped at the smaller of 15% above estimated maintenance or 500 calories per day. This exact cap is a MassMetrics guardrail, informed by conservative surplus guidance in resistance-training contexts [6].
Moderate deficits and commonly used intake ranges appear in adult weight-management guidance [4], but that does not make any automated target appropriate for every person. Final calorie targets are rounded to the nearest 50 calories.
Protein, fat, and carbohydrate
- Protein: 1.6 g/kg of reference weight, rounded to 5 g. This level is supported for healthy adults doing resistance training [7].
- Fat: 25% of calories, converted at 9 kcal/g.
- Carbohydrate: the calories remaining after protein and fat, converted at 4 kcal/g and rounded to 5 g.
For protein, reference weight is capped at the weight corresponding to BMI 30 for the entered height. This BMI-based cap is a MassMetrics safeguard—not a CDC protein recommendation. The CDC source is used only for the adult BMI 30 threshold [10].
The calorie conversions use general Atwater factors [9]. Adult acceptable macronutrient distribution ranges (AMDRs) provide broader context [8], but MassMetrics does not claim that the calculated carbohydrate result always falls within the carbohydrate AMDR—or that every coefficient is medically or clinically validated.
Extra walking and step targets
Extra walking is estimated at 100 steps per minute, added to your current baseline, then rounded to the nearest 500 steps. Research supports 100 steps/minute as a practical adult cadence heuristic [11]; it is not a personalized conversion. Actual cadence, distance, and energy use vary with stride, speed, terrain, mobility, and other individual factors.
Starter workouts
Starter workout splits, exercises, sets, repetitions, rest periods, and ratings of perceived exertion (RPE) are editable MassMetrics presets. ACSM supports broad principles such as progressive resistance training, covering major muscle groups, using multiple sets, and matching loading to goals [12]. That support does not mean ACSM endorses or clinically validates every exact MassMetrics preset.
Edits and overrides
All recommendations are starting points. You can replace individual calorie, macro, walking, or training targets. An override changes only that target and does not automatically rebalance the remaining targets, so review the full plan after making edits.
General healthy-eating guidance can provide context [13], but it does not validate MassMetrics’ formulas or guarantee an outcome.
References
These sources support specific formulas or broad principles as described above. They do not endorse MassMetrics or validate every product assumption and guardrail.
- 1.
Mifflin et al. A new predictive equation for resting energy expenditure in healthy individuals.
- 2.
Frankenfield et al. Comparison of predictive equations for resting metabolic rate in healthy adults.
Supports Mifflin–St Jeor as a useful adult estimate while documenting individual prediction error.
- 3.
National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Energy.
Supports treating energy needs as estimates affected by age, body size, sex, and activity.
- 4.
Jensen et al. 2013 AHA/ACC/TOS guideline for the management of overweight and obesity in adults.
Supports moderate calorie deficits and commonly used calorie-intake ranges.
- 5.
Wishnofsky; Hall et al. Static caloric equivalents and modern dynamic models of weight change.
Together, these explain the origin and limitations of static calorie rules.
- 6.
Iraki et al. Nutrition recommendations for bodybuilders in the off-season: a narrative review.
Supports conservative 10–20% surpluses in a resistance-training context.
- 7.
Morton et al. Protein supplementation and resistance-training adaptations: a systematic review and meta-analysis.
Supports approximately 1.6 g/kg/day for healthy adults performing resistance training.
- 8.
Institute of Medicine. Dietary Reference Intakes: macronutrient reference ranges.
Supports adult AMDRs of 20–35% fat, 45–65% carbohydrate, and 10–35% protein.
- 9.
USDA FoodData Central. Foundation Foods documentation.
Supports the general Atwater factors of 4 kcal/g protein, 9 kcal/g fat, and 4 kcal/g carbohydrate.
- 10.
Centers for Disease Control and Prevention. Adult BMI categories.
Cited only for the adult BMI 30 threshold, not for MassMetrics’ protein reference-weight rule.
- 11.
Tudor-Locke et al. Walking cadence and intensity in adults.
Supports 100 steps/minute as a practical population-level heuristic rather than a personalized conversion.
- 12.
American College of Sports Medicine. 2026 resistance-training position stand.
Supports broad principles including progressive training, major-muscle coverage, multiple sets, and goal-specific loading—not every MassMetrics preset.
- 13.
U.S. Departments of Health and Human Services and Agriculture. Dietary Guidelines for Americans, 2025–2030.
General healthy-eating context; it does not validate MassMetrics’ formulas.
Questions about our methodology?
Contact Discrete Software LLC at support@discretesoftware.com.