What GLP-1 actually is
GLP-1, short for glucagon-like peptide-1, is a hormone your gut releases after you eat. It tells your pancreas to release insulin, slows how fast food leaves your stomach, and signals your brain that you’re full. Drugs in this class copy that hormone’s effect, lasting far longer than the natural version, which breaks down within minutes.
Retatrutide and tirzepatide go further. Tirzepatide also activates the GIP receptor, and retatrutide activates GIP and glucagon receptors on top of GLP-1.
Why the effect changes week to week
Because these drugs are dosed weekly and titrated up gradually, the intensity of appetite and digestion changes shifts across the weeks of a course, not just from one injection to the next. That week-to-week shift is exactly what a log is useful for tracking.
Why so many people keep a log
Side effects, weight, and injection site all shift gradually over a course lasting months. Without a written record, it’s easy to lose track of what changed and when, particularly around a dose increase, since memory alone tends to blur weeks together.
What a useful entry tends to include
Date, dose, injection site, weight if tracked, and a short note on anything notable that week, side effects, energy, appetite. Simple and consistent beats detailed and sporadic.
The takeaway
Understanding how these drugs work also explains why the effect isn’t static, which is exactly what makes a week-by-week record worth keeping in the first place.