I have not seen any indication that Spike or similar compounds would have any benefit (either inducing or reducing) in weightloss.
It does help however with lethargy while dieting.
As for studying, I personnaly feel that Spike offers superior cognitive enhancement to an E/C mix. Caffeine could still technically be added for some added benefits (since there is only a little in Spike).
Also for studying and warding off tiredness, remember that smaller, more frequent dosing of caffeine is supposed to be superior (while reducing the crash some feel with large intakes of caffeine).
Good luck in your exam and your bulk,