I'm pretty sure the rates of hunger and malnutrition dropped significantly over that timeframe. I have no doubts that obesity is higher now, but also a lot less people are starving.
Being fat does not mean being sat or good fed.
China also got rich in that time. Do we have counterfactuals with which to disentangle Western food from wealth?
If some high% of people have a life improvement, a smaller % don’t, and an even smaller % end up obese.. that’s an overall improvement - even though some lives are worse than they’d have been without the “improvement”.
Of course if the majority became obese or otherwise became worse off, that’s a bad thing overall. But from what is reported it sounds like opening the Chinese economy has been net good, ie. good for most people.
In both situations one obesity case is too many. But it needs to be proportionally considered alongside the benefit it hitched a ride with and never in isolation.
It takes having numbers to know how much weight (sic) to place on that counterpoint of “some obesity happened”.