Biology
Caloric Intake
Quick fact
A single pound of body fat is roughly equivalent to 3,500 calories, meaning a daily surplus of just 500 calories can lead to a pound of weight gain per week.
Why this is interesting
You might think a calorie is just a number on a label, but it's actually a unit of energy that powers everything your body does—from breathing to running a marathon. How does the simple act of eating determine whether you gain, lose, or maintain weight?