Glycogen
The body's short-term carbohydrate store in liver and muscle — and the reason early 'water weight' swings happen.
Glycogen is glucose packed for storage — a day or two of fuel held in the liver (for the whole body) and muscles (for their own use). Each gram binds roughly three grams of water, which produces the famous scale behavior: start a diet or a GLP-1 medication, glycogen drains, water follows, and the first week shows a drop that isn't fat yet.
The same physics runs in reverse after a high-carb weekend — up overnight, equally not fat. Understanding glycogen converts scale volatility from discouragement into data: weigh trends over weeks, expect a fast first drop and a rebound bump or two, and reserve judgment for the slope, not the spikes.
This glossary entry is general information, not medical advice, and is written to be consistent with FDA prescribing information and primary trial publications as of its last review. Always consult a licensed healthcare provider for personal medical decisions.
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