"Charice's face, I've been noticing, it's been getting wider… That's why she looks mataba, although the body is very small, because your face is getting wide. One of the reasons for that, nagchew-chewing gum [siya]… Our chewing muscles, if you chew a lot of gums, it gets bigger," Belo said.
Blogger Ilda of AntiPinoy.com asks:
How big a factor does chewing gum play on the size of or amount of fat in people’s cheeks anyway?
Judging from the sort of information on the subject available on the Web, this is not an issue generally taken seriously by the medical community.
On wikiHow, the "advise" provided actually contradicts "Doctor" Belo's assessment and counts chewing gum as one of the measures available to help one "lose weight from [one's] cheeks".
A similar query into the effects of chewing gum on the appearance of one's cheeks was posted on the "Weight Loss" section of About.com. Comments were mixed and, therefore, inconclusive. Some of the commentors suggested that its effect is just a figment of the imagination or just "all in [the] mind".
By far the most perceptibly well-thought-out response I found was in Yahoo! Answers in response to the question "Do you think chewing gum makes u loose [sic] weight from your cheeks therefore causing the appearance of cheek bones?". It was the "best answer" selected by the asker:
Although any form of activity burns some calories, chewing gum will not impact your weight dramatically enough. Since weight comes off evenly all over the body (and we can't "spot reduce"), you'll need to lose weight overall in order to thin out your face. Cheekbones also have a lot to do with your bone structure, so although losing weight may cause them to be more prominent in appearance, in reality, you can't "create" the appearance of high or prominent cheekbones if you don't already have them. There are many women who are very thin but still have a rounder or less angular face.
Bottom line is that there is no authoritative take on the subject that trumps the dubious armchair "expertise" that come up in a quick Google search. Perhaps, as I suggested earlier, it is because the subject does not warrant serious consideration by a serious medical practitioner. That said, even the response above by a casual commentor is even better than the public assessment made by "Doctor" Vicki Belo.
But that's not really surprising considering ours is a society addicted to mediocrity even in professions that impact people's lives.