Nutrition Meal Plan Recommender Calculator

The chain here runs from resting metabolism outward. Mifflin-St Jeor estimates basal metabolic rate from weight, height, age and sex, with a constant of plus 5 for men and minus 161 for women; most adults land between about 1,200 and 2,000 kcal. Multiplying by an activity factor from 1.2 for sedentary living to 1.9 for heavy physical work gives total daily energy expenditure, and the goal adjustment of plus or minus 250 to 500 kcal sets the target intake. Macronutrient grams follow the Atwater factors of 4 kcal per gram for protein and carbohydrate and 9 for fat. Fibre is set at 14 g per 1,000 kcal following the Dietary Reference Intakes, fluid at roughly 33 mL per kg of body weight, and projected weight change uses the convention of 7,700 kcal per kilogram. The reference values shown are population standards, not personal prescriptions: 2,300 mg is the upper sodium limit in the Dietary Guidelines for Americans, calcium sits at 1,000 to 1,200 mg depending on age and sex, vitamin D at 600 IU rising to 800 IU past 70, and iron at 18 mg for premenopausal women against 8 mg otherwise. Protein RDA is 0.8 g/kg, while sports nutrition bodies recommend roughly 1.4 to 2.0 g/kg for training athletes. Accuracy is the main caveat. Predictive BMR equations fall within about 10 percent for most people but perform poorly at the extremes of body composition because they use total mass rather than lean mass. Activity level is self-reported and habitually overestimated, and metabolic adaptation blunts a deficit over months.

The energy accounting behind every nutrition label came from Wilbur Olin Atwater, who built respiration calorimeters at Wesleyan University and the US Department of Agriculture in the 1890s and derived the 4, 4 and 9 kilocalorie factors still used for protein, carbohydrate and fat. Basal metabolism became a clinical measurement in the following decades, and in 1919 J. Arthur Harris and Francis Benedict of the Carnegie Institution of Washington published the regression equations that carried their names and dominated dietetics for seventy years. Harris-Benedict was fitted to a small, comparatively lean early twentieth century sample and tends to overestimate requirements in modern populations. In 1990 Mark D. Mifflin, Sachiko St Jeor and colleagues published a replacement in the American Journal of Clinical Nutrition, derived from indirect calorimetry on 498 healthy adults, and a systematic review by the American Dietetic Association in 2005 concluded it was the most reliable predictive equation for non-obese and obese adults, which is why it is the default here. The energy-per-kilogram conversion traces to Max Wishnofsky's 1958 paper deriving 3,500 kcal per pound of adipose tissue, a figure now understood to overstate long-term loss because expenditure falls as body mass drops. The Dietary Reference Intakes for fibre, calcium and vitamin D were issued by the Institute of Medicine between 1997 and 2011.