The urban areas in 2010 had significantly higher obesity rates than even the rural areas in 1990. So regardless of what people are yapping about, it's not working.
Almost everyone over 30 has some level of gut now, even those considered comparatively fit and thin. This wasn’t normal decades ago, but is normal now.
How often do you see people shirtless? Clothes hide a lot of bellies. Having muscles, being a jogger, eating salads or riding s bicycle is completely consistent with abdominal fat.
So, what standard are you using when you say urban people now are likely thinner than rural people in 1990?