A cell biologist or molecular biologist focused on studying mitochondrial function and disease, likely working in an academic research setting or biotechnology industry.
While browsing the shops today, I was struck by the sheer number of products promising to boost cellular energy.  It's a testament to how much the public is finally recognizing the importance of mitochondrial health and its impact on how we age and on many health problems, but let’s be careful and support only scientific solutions.