The microbiologist is the professional who works with microbiology.
Microbiology is the area of biology dedicated to the study of microorganisms. It analyzes their functions, characteristics, metabolizations, distributions and their effects. It can also be characterized as a specialty of biomedicine that studies pathogenic microorganisms, ie those that cause infectious diseases, thus encompassing bacteriology, virology and mycology.
In this case we can say that if Bijoy wishes to pursue a career in a field where he can study various microorganisms and diagnose various disorders using microbial analysis. He must follow the career of microbiologist.
If they want to gain loose weight then they would need to eat well, so taking in a normal amount of calories but exercising more. To gain wait, take in more healthy calories but not that much of an extreme work out.. Hope this helps.