Healthy Weight (visual assessment) of a Leopard Frog?

[NiciCool]

Hello everyone. I have a little leopard frog who I got as a tadpole just over a year ago. Kermit (or Mr. The Frog) is a good eater (except in the winter, when he goes into long periods of torpor), and seems relatively self regulating food-wise, but recently I've been concerned about his weight. Part of the problem is that I can't seem to decide whether he is under or overweight. When he is crouched, he seems nice and fat (sometimes a bit too fat - usually after he's just eaten), but then when he's stretching out and jumping for crickets he seems too skinny. Are there any particular indicators that can tell me if he is at a healthy weight? Back ridge prevalent/not prevalent, round stomach/flat stomach, etc? Thanks in advance!