every regain-panic thread has someone post a number like this and the replies go straight to shame management, which is fine, but nobody runs the actual arithmetic and the arithmetic is the thing that should calm you down. 15 lb of fat is roughly 52,500 kcal of surplus (the ~3,500 kcal/lb figure is a rough lab number, not gospel, but it’s the right order of magnitude). over 7 days that’s a 7,500 kcal/day surplus on top of maintenance. nobody bored-eating goldfish is clearing 9,000-10,000 kcal a day for a week straight. the body physically can’t lay down fat that fast from food intake. so whatever the scale said, it is not 15 lb of fat. full stop. what it actually is, and this is two separate things stacked, not one: glycogen binds water. every gram of stored glycogen pulls ~3-4g of water with it. when you eat at maintenance plus carbs after a depleted GLP-1 week, you can refill liver and muscle glycogen and that’s a few lb of water swing on its own. a paper i read on day-to-day weight variability had healthy adults swinging 1-2 kg between days with no change in fat mass at all, just fluid and gut content. the second clock is gut transit. food in the lumen has weight. a high-sodium high-carb week with less movement = more retained water + more undigested bulk sitting in you. that reads on the scale instantly and clears in days. where this connects to the compounded sema/tirz crowd specifically: the drug suppresses intake hard, so your glycogen runs low and your baseline scale weight is artificially deflated. a normal-eating week doesn’t make you fat, it un-deflates you back to your real hydrated weight. the rebound looks violent because the floor was fake. the practical read: don’t weigh during or right after a high-stress eating stretch and treat it as fat data. it’s noise riding on a real but slow signal. if you want the actual trend, weigh same time of day, same conditions, and look at the 2-3 week line, not the day. a 15 lb single-week spike is fluid telling you you were dehydrated-low before, not fat telling you you failed.