Energy Balance Lab

How the model works: basal metabolic rate (BMR) is estimated from lean mass (370 + 21.6 × lean mass in kg, a published equation). Resting energy use per kg of lean mass is held steady until about age 60, then lowered about 0.7% per year, based on large recent studies; much of the real change with age comes from losing lean mass, which you can show with the lean mass slider. Total = BMR × activity level; the thermic effect of food is set at 10% of the total, assuming intake matches use. Sleep slightly lowers energy use while asleep, and fewer hours of sleep leave more awake hours for movement. A cool room adds a small amount of adaptive thermogenesis. Organ shares are approximate textbook values. Simplified for learning.

A teaching model. Curves are drawn on a 0 to 100 relative scale to show timing and direction, not measured blood levels, and real people vary a lot. Meal types differ in how strongly they trigger fullness hormones; none is "good" or "bad". Short sleep raises ghrelin and lowers leptin by roughly 15% in the model, based on sleep studies.

The picture updates with the answer you type. The worked solution builds step by step; units that cancel are struck out in red. All figures are rough population values for learning.