>There was a massive (18,000,000 people) cohort analysis published in 2023 that showed the likelihood of someone losing 5% of their body weight in any given year was 1 in 11

Unsurprising. They ran statistics on arbitrary overweight and obese people, with no idea of who was actively seeking to lose weight or who was just coming away from such an effort. If a significant fraction of the overweight/obese population did lose 5% of body weight/year, we wouldn't be seeing a bunch of overweight/obese people.