Riddle me this, people who understand physiology. My watch tells me I burn more calories when I work out in the evening compared to when I work out in the morning.

Makes sense – I pop a beta blocker in the morning, which prevents my pulse from really exceeding 140 regardless of how hard I push myself, while in the evening I easily get over 175. The watch, of course, cannot really rely on much other than the pulse to determine the effort. The difference according to my watch is as much as 50% more burned in the evening.

However, I typically do very similar workouts: the same amount of time on the same spinning bike at the same load and speed. Physically, I perform the same amount of work regardless of whether it is in the morning or evening.

Now, I wonder, which of the two are closer to the truth (realizing that the truth is somewhere in the middle and blahblah)? Do I burn roughly the same amount of calories (at least during the workout) because I perform the same amount of work? or it is way better to do it in the evening because my body is running in a higher gear?