You can't base your perception of an entire ethnicity on videos you've seen on social media. I visit Somalia on regular basis and even though plenty of Somali girls bleach their skin they're not fat. I would say less than 5% of girls between the age 17-35 are fat. Most of them are skinny tall chicks from poor to middle income families.I haven’t been. I’m basing it on all the videos I’ve seen on TikTok, surely it must be common. Maybe not the majority but common enough.
Just visit the country once and see it for yourself.