I have done a bit of tinkering-installed Malwarebytes and kicked the trial on-to get some data on it.
First of all, Malwarebytes does not run under any "Antimalware Service Executable", it has its own "Malwarebytes Service" located under "C:\Program Files\Malwarebytes\Anti-Malware\MBAMService.exe".
However, Windows has its own "Antimalware Service Executable" under "C:\ProgramData\Windows Defender\Platform\<version>\MsMpEng.exe" which supplies real-time protection if there is no other AV that offers this. (Theoretically, this means it'll kick up in the free version of MB. Did not confirm though. All I know is that the trial version is recognized as a proper AV.)
That said, MB has a noticeable weight when scanning, and does easily hoard a %40-%50 memory-CPU time on my entry level laptop. Still though, %83 is absurd (may be too low specs too, I'd take this with a grain of salt) and a full reinstall of the AV may fix it.