That made me wonder: did any of the studies find significant reductions in cellular function? My analogy is a car rated at 200 hp on fuel brands A to W, and measures only 100 hp on brand X. Is there an equivalent of a dynamometer that can measure power output of muscle cells, or brain cells or whichever, and has that been done for cells of PWME vs sedentary controls?
Finding small changes in mitochondria (fragmentation ,etc) might be important in ME, or it might not. To follow the previous analogy, I can imagine a study finding that fuel X "leaves a sticky residue on the carburetor shaft, which could hamper throttle movement and thus reduce power!" ... yet dynamometer testing shows no reduction in engine power, because all stickyness does is insignificantly increase the foot pressure required. Meanwhile, the study was funded by fuel A's company, or a company that sells a really profitable fuel additive claiming to clean out sticky residue.
Measuring overall muscle power isn't adequate, because that can be affected by many factors other than mitochondrial function. For example, if the muscles were getting conflicting signals, there'd be a lot of usage byproducts (heat, lactate, etc), but reduced physical power output.
I'm questioning whether mitochondrial dysfunction has been proven to be a cause of ME symptoms, rather than just a theoretical possibility.