In the US, the percentage of children five years of age and under that were obese, dropped from 14% to 10% over ten years (2004-2014). That's due to first recognizing a terrible problem and then acting against it.
US obesity rates have stabilized. [1] I think we can be fairly certain that's in no small part due to increased knowledge and awareness of the problem over the last decade. The next step is to begin moving the needle the other direction, even if it's a slow process.
People think obesity in the US is a very old problem, when in fact it started just 30 years ago and wasn't a serious issue until the late 1990s. In 1985 no state had an obesity level over 15%. Today, 46 states exceed 25% obesity. I doubt the US will ever go back to 1985 obesity levels, however if it can change negatively that much in less than two decades, then you can plainly see meaningful improvements in a similar amount of time.
[1] https://www.rwjf.org/en/library/articles-and-news/2017/08/ne...