hi ankur,
factors like weight n height doesn't come into picture for doing a mining btech from bhu as u just hav to do courses in d same way as u hav done if u r in some other branch,,,
yes weight factor may come in account when u opt for jobs in d mining companies , in dis case i will suggest u dat u can increase ur weight as u hav got 4 years wid u so don't bother about dis issues now..also if u don't opt for mining companies den u needn't hav to concern about ur weight or height..
						

							
Hi
Relax, its not such that u'll be made to do mining . The job do requires field work and is a bit exausting but u'll be doing an engineers job , not the mining. U'll need to design and plan the thing and supervise them. Also, its 4 yrs of engg. , u can work on ur health too. 
Moreover the institute sets a minimum criteria for health during the admission, if u are above that then u can definitely apply for the course. If u are still too much concerned about it and do not feel safe , then go for the NITs or any other good institute .