High rates of energy production (requiring high rate of ATP production) as occurs in weighlifting – any work rate that’s hard enough that it cannot be sustained for long at all – requires glucose as the principal fuel.
This does’t have to be from dietary glucose, but can be from glucose produced from some of the amino acids of protein.
(The reason I mention that is without a person knowing of this alternate source, they might assume that a low-carb diet would leave high rate energy production impossible, but that’s not the case.)
So during the time the muscles are working quite hard, fat is not their principal fuel. (Though they can use fat to so-to-speak recharge ATP stores, which when at maximum capacity can provide a number of seconds of high energy output. And this goes on while resting or working only rather easily. But they can’t use fat fast enough to support ongoing high-output work.)
However, the calories burned are calories burned and will result in fat being burned overall.
It shouldn’t really matter to the person exercising, other than theoretical interest, whether fat is being burned at the moment or will be consumed later.
You will not see a noticeable difference in body fat after any individual workout of any reasonable length.
For example, suppose you burn 1200 calories, which would be a lot of working out. Probably two hours of working quite hard. And suppose we wait enough time so that protein and glucose/glycogen levels are restored, so by now it’s all fat loss. That corresponds to about 1/3 of a pound of fat. You cannot see that.
I did once see a video someone produced of their losing 1 lb of fat in a day with something like 9 hours on the treadmill. This person was so lean in the first place that 1 lb actually was visible.
So if one wants to take things to the fairly ridiculous, then it is possible in such cases to have a noticeable small difference from “one workout” but certainly in any ordinary circumstance, no, as a shorter single workout cannot burn enough calories to represent a noticeable amount of fat.
It sounds like you’re hoping for something way too much.
Why not consider the cumulative effect of 3 or 4 workouts per week, thus about 13 to 17 workouts per month, over a few months so then say 40 or 50 workouts?
Now, individually invisible small losses of fat add up to something very noticeable.
On top of that, a fat loss program should involve fat loss on an ongoing basis as well, not simply from calories burned while working out.