Should You Tell Someone They Don't Look Like Their Photos?

What's the etiquette when you meet someone for the first time via an online dating website, and you can clearly see he or she is much heavier than the pictures he or she posted online? I'm not talking a few vanity pounds, I mean about 20 or more pounds heavier.
Like most people, I have had this experience several times, and by now I'm wondering how acceptable or rude it will be to just say, right off the bat, "Sorry, but you're not what I was expecting, I do not think you look like your pictures," and walk away.
I know it's a harsh thing to say to someone in person, but I feel like the other person was in the wrong to begin with by using very old pictures to misrepresent him or herself.
I'm baffled by people's inability to have a brief interaction with a stranger without seething with contempt. I get it. It's frustrating to expend the time and effort exchanging messages and traveling to meet someone only to find out they misrepresented themselves. Navigating dating apps and dating sites is hard enough without these sorts of speed bumps. Point taken.
However...
Has it occurred to you that the issue goes a little bit deeper?
As many know, we host speed dating events in NYC and Boston. Each event has an assigned age range that we ask people to request. While 90% of registrants for each event fall within the stated age range, there's always those 1 or 2 people that don't. As a result, we often receive emails from people complaining that there was that one out of 9-12 people they met that "looked much older" than the age range. Pay attention to the verbiage. The complaint isn't about the age itself, but what the person looked like. In at least half of these situations, we check the ID of the person who was allegedly outside the age range. Guess what? They weren't.
Something about having to sit across from a man or woman that looks outside of what we think is our league triggers certain people. My theory is they are literally face-to-face with a reality - aging, that they're no longer able to attract the types of people they used to, mortality - they are not ready to confront.
Should you weight or age-shame your date in person because you lack the social skills to engage in a pleasant conversation for an hour? Sure. Go ahead. Be that guy or girl. Just know the searing embarrassment they're probably going to experience during and afterwards. She didn't steal your identity, my dude. She committed the egregious crime of putting on weight.
Sometimes people intentionally mislead because they knew if they didn't, they wouldn't get many matches. Your date was 5'7" not 5'9'"? They were 50 and not 45? A size 16 and not a 12? They only make 60K a year? Poor you. Are you okay? Do you need me to call someone for you? Now try to imagine how it feels to have your entire self-worth revolve around a set of numbers.
More than likely, she has no idea she looks nothing like her photos. There are legions of men and women out there who insist they look ten years younger than they are or can pass for a certain age or weight. When you look at yourself in the mirror everyday, it's difficult to see a change. You might feel it, but you don't necessarily see it. Unless you switch out your dating profile pictures every couple of months, I guarantee you there's something about your appearance that has changed since you uploaded photos. Few people ever look exactly like their dating profile shots. Angles, make-up, clothing, lighting all play a factor.
As I said in the beginning, I understand why you feel compelled to word-vomit your annoyance at this woman. I'm not against speaking up, as long as it's done humanely and with as much compassion possible.
"Hey there. It was great to meet you last night. Unfortunately, I don't think we're a match. You seem really great, but I wanted to let you know that you might want to update your photos."
That will be enough for them to review their pic selection with a more critical eye, should they be open to doing so. The thing to realize is this gentle suggestion will probably be ignored. These people showing up looking vastly different than their profile pictures either are oblivious to the discrepancy or truly believe there's no difference between their photos and what they look like in person. And then there are the few who are knowingly being misleading because they want a chance to be seen.