The BMI cutoff at 25 for overweight and 30 for obese is fairly arbitrary. People in different nations, and people in different time periods, have different standards. And we know that the effect of adiposity on lifespan and health is continuous with respect to body fat percentage, at levels higher than those characteristic of very lean bodies.
The phenomenon in need of explanation is why our wastelines got larger over time. Once we provide an explanation for that phenomenon, it’s no mystery why there is a discontinuity in the obesity chart at 1980. That’s merely an artifact of the arbitary cutoff. Overall I see no deep mystery that demands explanation above and beyond rising adiposity during the 20th century. Is it your position that we ought to be find the discontinuity at 1980 mysterious anyway?
ETA: I realize now I gave short shrift to your point about the data series ending around 1980. I actually think it’s ~1986 but it’s still hard to interpret the last six years. I’ll edit my other comment to reflect this oversight.
The BMI cutoff at 25 for overweight and 30 for obese is fairly arbitrary. People in different nations, and people in different time periods, have different standards. And we know that the effect of adiposity on lifespan and health is continuous with respect to body fat percentage, at levels higher than those characteristic of very lean bodies.
The phenomenon in need of explanation is why our wastelines got larger over time. Once we provide an explanation for that phenomenon, it’s no mystery why there is a discontinuity in the obesity chart at 1980. That’s merely an artifact of the arbitary cutoff. Overall I see no deep mystery that demands explanation above and beyond rising adiposity during the 20th century. Is it your position that we ought to be find the discontinuity at 1980 mysterious anyway?
ETA: I realize now I gave short shrift to your point about the data series ending around 1980. I actually think it’s ~1986 but it’s still hard to interpret the last six years. I’ll edit my other comment to reflect this oversight.