The more important question is how can you be sure the data from Pakistan on obesity is sampled exactly same as the data from India and Bangladesh or vice versa

The more important question is how can you be sure the data from Pakistan on obesity is sampled exactly same as the data from India and Bangladesh or vice versa. Like a friend of mine said: "nobody ever measured my height and weight recently, so how can we trust the recent obesity data?". Granted, the discussion wasn't about obesity but about the chart on EU penis size variance between countries, but you get the point.