I think it’s too much aerobic cardio and not enough anaerobic (weight lifting) is the main reason[1], you may burn fat but your just going around in circles to gain it all back again without increasing muscle volume in contrast to diet?
Like eating window time frames, what your eating and the amount your eating?
For example back in the 80’s If you eat at the wrong time after working out, there is a window that allows you to heavily carb up without it being stored as fat but if you don’t catch that window you get fatter!
Hopping and prancing around in cute high cut shiny leotards (own quite a few) can be fun too but you need to do stuff like this too (working the glutes):
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References:
[1] “…An MRI of both legs post-programme revealed the muscles in legs subjected to extra cardio work increased in volume by 14% and 17%, compared to 8% and 9% in the legs put through just strength work. …” …More