Not at all. Jeezus no.
First: No one knows WHY they're fat to begin with. And it isn't an employer's business. If they cannot do their job and were once able to, that's one thing.. but my sister is skinny as a tooth pick, and sick as shit. My mother is "fat" but because of life saving medicine that's made her 10x stronger (and 100% surviving) than she was before when she was skinny with an undiagnosed illness.
Second: Morbidly obese people need to make money too. Skinny people can be bad at math (and thus slower cashiers), and thus drive down productivity the same way a fat person can need a few more breaks to rest their feet. The reality is businesses discriminate all the time based on shit they shouldn't because it's bad for business. People need to fucking care about their damned employees. People need to not be scared of revealing medical issues. I am lucky in that I get to hide mine. I LOOK healthy, but any second my hip can lock up and suddenly voila: I can't walk. If I told anyone hiring me that they wouldn't. Not a great thing to have when you have a career where people depend on your ability to get to them quickly. But what's the alternative? Just give up? Not be productive the other 99% of the time because it could possibly happen? And I'd be feeding and leeching off of the system trying to claim all sorts of disabilities and why I can't work because no one will hire me, and these same business owners that discriminated against me will bitch and whine that I'm using tax dollars instead of paying taxes.
Third: It's none of their fucking business, and businessmen are always hypocrites. As long as they can DO the job, why the fuck would anyone care ever. Especially now-a-days where health care is becoming mandatory no matter what. Bunch of skanky shank-worthy fuckers crying about how fat people are ruining their businesses and lives so they can only have 3 turkeys at christmas dinner this year. The CEO of abercrombie and fitch or whatever they're called was making mad shit about being all "omg hot people only plz kthnx no fatties" and the fucker wasn't hot or in shape by his own standards at all. It's stupid. Fat does not determine health, but fat people are more likely to accept help medically than skinny people. It's the stupid skinny people that need more convincing.
Fourth: Studies have always shown that more doctor visits correlate to better health. Areas without doctors or people who rarely visit the doctor tend to have less contact with a vital source of information on health. And say the skinny person never uses it, but their kid is sick and they use it all the time for the kid? This data is heavily skewed in favor of a particular skinny agenda.
The data is skewed, it's a bullshit way to discriminate against fat people, and it's all garbage. The end.