Not only Malaysia Airlines has obese cabin crew but SIA too. Sacking is too drastic but like what SIA is going to do is more reasonable. Obese stewardesses are affectionately nick named PPS or Pui Pui Stewardesses. PPS is actually the acronym for SIA regular passengers (Passenger Priority Service).
In March this year, Air India grounded 34 obese cabin crew, 30 of them of female and 4 male.
Since SIA has excess crew, grounding the obese ones would not affect the rostering process.