Sources & Methodology

At Gymbers, we want every recommendation we surface to be grounded in published evidence. The calculations and guidance below — body mass index, daily calorie and macronutrient targets, strength standards, and training methods — are based on peer-reviewed research, public health bodies, and recognized strength and conditioning literature. Our coaches and engineers reference these sources when designing the features inside the app.

BMI and weight assessment

Gymbers calculates body mass index (BMI) as weight in kilograms divided by the square of height in meters, and groups the result into the World Health Organization's adult classifications (underweight, healthy, overweight, obese). BMI is a population screening tool. It does not directly measure body fat and does not account for muscle mass, bone density, or body composition, so it should be interpreted alongside other health indicators.

• A healthy lifestyle — WHO recommendations: Body mass index.World Health Organization, Regional Office for Europe.
• Assessing your weight.Centers for Disease Control and Prevention.
• Physiology, Body Mass Index.Zierle-Ghosh A, Jan A. StatPearls. Treasure Island (FL): StatPearls Publishing; 2023.
• Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults.National Institutes of Health. Obes Res. 1998 Sep;6 Suppl 2:51S-209S.

Nutritional goal setting

When you set up nutrition targets, Gymbers estimates your basal metabolic rate (BMR) using the Mifflin-St Jeor equation, then multiplies BMR by an activity factor to estimate total daily energy expenditure (TDEE). Your daily calorie target is TDEE adjusted by a deficit or surplus depending on your fitness goal. Macronutrient grams are derived from your calorie target using the Atwater energy values (4 kcal per gram of protein and carbohydrate, 9 kcal per gram of fat). These outputs are estimates — your true energy needs depend on individual physiology, body composition, and activity outside training.

• A new predictive equation for resting energy expenditure in healthy individuals.Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. Am J Clin Nutr. 1990 Feb;51(2):241-7.
• Human energy requirements — Report of a Joint FAO/WHO/UNU Expert Consultation.Food and Agriculture Organization of the United Nations, Rome, 17–24 October 2001. (Activity-level multipliers for TDEE.)
• Food energy — methods of analysis and conversion factors.FAO Food and Nutrition Paper 77. Rome, 2003. (Atwater general factors: 4/4/9 kcal per gram for protein, carbohydrate, and fat.)
• Quantification of the effect of energy imbalance on bodyweight.Hall KD, Sacks G, Chandramohan D, Chow CC, Wang YC, Gortmaker SL, Swinburn BA. Lancet. 2011 Aug 27;378(9793):826-37. (Basis for calorie deficit/surplus targets.)
• Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids.Institute of Medicine of the National Academies. National Academies Press, 2005.
• Dietary Guidelines for Americans, 2020–2025.U.S. Department of Agriculture and U.S. Department of Health and Human Services. 9th Edition.

Strength standards and 1RM estimation

Gymbers estimates your one-rep max (1RM) from sets you log using the Epley and Brzycki repetition-based equations, and compares your strongest lifts to population standards using a Wilks-style normalization that adjusts for bodyweight, age, and gender. Estimated 1RM values become more accurate as the number of reps decreases, and strength categories (untrained, novice, intermediate, advanced, elite) are population benchmarks rather than medical assessments.

• Poundage chart.Epley B. Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985. (Original publication of the Epley 1RM formula.)
• Strength testing — predicting a one-rep max from reps-to-fatigue.Brzycki M. Journal of Physical Education, Recreation & Dance. 1993;64(1):88-90.
• Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry.Reynolds JM, Gordon TJ, Robergs RA. J Strength Cond Res. 2006 Aug;20(3):584-92.
• The Wilks Coefficient — bodyweight-normalized strength scoring.Wilks RA. Originally adopted by the International Powerlifting Federation in 1994. (Used as the basis for cross-bodyweight strength comparison.)

Workout programming and training methods

Recommendations around warm-up sets, repetitions in reserve (RIR) and rate of perceived exertion (RPE) targets, set types (warm-up, working, drop set, set to failure), and rest periods are drawn from standard strength and conditioning literature and peer-reviewed exercise science. They are general guidance — the right protocol for any individual depends on training experience, recovery, and goals.

• NSCA's Essentials of Strength Training and Conditioning, 4th edition.Haff GG, Triplett NT, editors. National Strength and Conditioning Association. Champaign, IL: Human Kinetics; 2016. (Warm-up structure, set/rep prescription, rest intervals.)
• Novel resistance training–specific rating of perceived exertion scale measuring repetitions in reserve.Zourdos MC, Klemp A, Dolan C, Quiles JM, Schau KA, Jo E, Helms E, Esgro B, Duncan S, Garcia Merino S, Blanco R. J Strength Cond Res. 2016 Jan;30(1):267-75. (Foundation for RIR/RPE scale.)
• ACSM Position Stand: Progression models in resistance training for healthy adults.American College of Sports Medicine. Med Sci Sports Exerc. 2009 Mar;41(3):687-708. (Set type and progression guidance.)
• Strength and hypertrophy adaptations between low- vs. high-load resistance training: a systematic review and meta-analysis.Schoenfeld BJ, Grgic J, Ogborn D, Krieger JW. J Strength Cond Res. 2017 Dec;31(12):3508-3523.
• RPE and velocity relationships for the back squat, bench press, and deadlift in powerlifters.Helms ER, Storey A, Cross MR, Brown SR, Lenetsky S, Ramsay HD, Dillen C, Zourdos MC. J Strength Cond Res. 2017 Feb;31(2):292-297.

Recipe nutrition

Recipe calorie and macronutrient totals are computed by summing the per-100 g nutritional values of each ingredient (sourced from public food composition databases such as USDA FoodData Central and Open Food Facts) and scaling to the recipe and serving size you log. The same Atwater energy values used for your nutrition goals (see Nutritional goal setting) apply.

• USDA FoodData Central.U.S. Department of Agriculture, Agricultural Research Service.
• Open Food Facts.Open, collaborative food database covering more than three million products worldwide.

Updates to these sources

We revise this page as the underlying evidence evolves and as new features are added to Gymbers. If you spot a citation that needs updating or have a question about how a calculation is made, please reach out at contact@gymbers.com.