In reply to the original topic, I'd say I pity those folks in general. There's a reason most people gain a pound a year after age 25; eventually their body will become unable to deal with all that crap.
I do get annoyed when they try to insist that what they're doing is healthy. But mostly people like that aren't conscious enough of their habits to have made a decision about whether they're trying to be healthy or not; more probably they're just trying to stay thin, although they'll insist they're healthy if asked.
The people I get more annoyed at are the carb-shovelling marathoners who insist that 1) Eating a ton of carbs is the peak of nutrition, and necessary for any athleticism, be it weightlifting or aerobic, 2) Running a marathon, which killed its first participant and continues to kill several each year, is the epitome of modern health, no matter how flabby your skinny runner's body is, and 3) I am crazy, and eating a diet like this will kill me, and I'm touched in the head for even suggesting the lipid hypothesis isn't true, regardless of how many peer-reviewed publications I have backing me up.