AM Detector Peak Vs Average
You cannot demodulate an AM signal by averaging it - Assuming that's what you're asking.

If you filter an AM signal with a LPF the amplitude of the carrier becomes suppressed, thereby also suppressing the envelope of the carrier, hence loosing your modulation  signal.
This should make sense when looking at the transient depiction of an AM signal. 
The only way of demodulating AM is by envelope extraction, and the simplest electronic circuit for that would be a rectifier.
There are better ways of envelope extraction that give better SNR but at the cost of more circuit complexity.