It's something fat people do to lose weight.
I'm pretty fat myself.
I'm not fat, I have an okay diet and I'm probably just one of those types that doesn't get fat easily... not yet anyway.
However I'm extremely weak. My knees tend to ache for 12 hours if walk around for more than 20 minutes, and three days a go I put my back out when I leaned back a bit weird.
Pretty sure if I got hit by a car I'd fall to pieces. I'll do something about it... some time some decade. LOL.