What it means
Muscles adapt to the work you give them. Once a load feels easy, it stops being much of a challenge. Progressive overload means nudging that challenge up over time, for example by adding a little weight, one or two more reps, an extra set or slower, more controlled movements.
The US Physical Activity Guidelines describe overload and progression as core training principles and advise increasing activity gradually to lower injury risk. They recommend muscle-strengthening work for all major muscle groups on 2 or more days a week.
Progress does not need to be fast. Small, steady steps work well, and a simple log of exercises, weights and reps makes the trend easy to see.
During weight loss, simply holding your strength steady can be a win, since strength is harder to build in a calorie deficit. Back off if you feel joint pain, dizziness or unusual fatigue.
Why it matters
Steady strength gains are one of the best signs you are keeping muscle while losing weight on a GLP-1.