Understand the numbers.
Build habits that last.

01 / Energy balance

Weight change happens over time.

Sustained energy intake below expenditure generally reduces stored body energy; sustained intake above expenditure increases it. Food quality, activity, sleep, medications and health conditions also matter for a workable plan. A calorie calculation alone cannot explain every change on the scale. NIDDK: eating and activity.

As weight and activity change, energy needs change too. Progress will not follow a fixed “calories removed = pounds lost” rule indefinitely. The research behind NIDDK’s Body Weight Planner accounts for this changing physiology.

02 / Your energy estimate

BMR, resting energy and TDEE.

Our calculator uses Mifflin–St Jeor to estimate resting metabolic rate (RMR), often labeled “BMR” in everyday calculators. It does not measure metabolism. The original equation used weight, height, age and male/female coefficients in adults aged 19–78; individual needs can differ. Original Mifflin–St Jeor study.

Total daily energy expenditure (TDEE) combines resting energy, movement and digestion. Choose one portal method:

• Activity multiplier: this already includes activity and digestion. Do not add workout calories again.
• All-day active calories: use activity above rest, not workout-only or device-total calories. Our illustrative estimate is (resting + active) ÷ 0.9, assuming digestion uses 10% of total expenditure.

That digestion allowance is an approximation; meal composition and other factors change it. Wearable estimates also vary. National Academies: components of energy expenditure.

03 / Food logs

Useful information, with room for error.

Check serving amounts, brands, preparation methods, drinks and added oils. Review text read from screenshots or dictation before saving. The portal’s calorie estimate uses the information supplied; an incomplete diary cannot establish a calorie deficit. Our logged-day average describes saved entries, not verified total daily intake. NIDDK’s planner also explains intake-estimation limits.

04 / The scale and the bigger picture

One reading is only one observation.

Water and glycogen shifts can change weight without an equivalent change in body fat. Look at repeated measurements under comparable conditions. The portal’s optional repeated weigh-ins check consistency in one sitting; they do not reveal body composition. Research on day-to-day body-mass variation.

Record gym loads using the same exercise, equipment, repetitions and load basis. Band color alone is not a pound-equivalent. Strength practice is valuable alongside regular movement and eating habits. NIDDK: muscle-strengthening activity.

05 / Body composition

Keep measurements and estimates distinct.

Fat-free mass includes muscle, water, organs and bone. A change in fat-free mass is not proof of muscle gain. Enter skeletal-muscle estimates separately with their device and method. Compare the same source and similar conditions.

Our portal photos document appearance; they do not calculate fat or muscle. Even studied image-based systems have individual estimation error. Primary research on smartphone body-composition estimates.