Yes, fat does not keep fatties warm in winter, though I'm pretty sure the only claimed and plausible benefit of being fat is having calories to survive on during extended forced fasting. It used to be a critical part of survival during periods of famine but in modern times it does more harm than good. Nowadays, the only times it could be of any good would be if you got cancer where eating and/or keeping food down becomes hard, any other illness that makes keeping food down hard or if for some really rare reason you find yourself stranded on a remote place without food and end up staying there for a long time.