Energy balance
Body weight changes over time according to the relationship between energy from food and energy the body uses.
Main idea
When a person repeatedly eats more energy than they use, the body does not simply remove that excess. It uses energy for immediate needs and can store the rest.
The body uses energy for movement, brain activity, body temperature, digestion, tissue repair and many internal processes that continue even at rest.
Glycogen and fat
Some carbohydrate can be stored as glycogen in muscles and the liver. This is a quick but limited reserve.
When available reserves are sufficient and excess energy is repeated, the body can store more energy as body fat.
Scale weight is not only fat
- more body water;
- more food in the stomach and intestines;
- more glycogen, which holds water;
- more salt, which can increase fluid retention.
Simple rule
Short-term weight changes are noisy. The useful signal is the trend across days and weeks, together with food intake, activity and body measurements.
Source
- WHO healthy diet : Healthy diet fact sheet.
- Dietary Guidelines for Americans : Common questions about saturated fat and dietary patterns.