Guyenet, who’s palatability theory you seem to prefer, shares the same interpretation as SMTM. His chart from The Hungry Brain:
And his commentary:
In 1960, one out of seven US adults had obesity. By 2010, that number had increased to one out of three (see figure 2). The prevalence of extreme obesity increased even more remarkably over that time period, from one out of 111 to one out of 17. Ominously, the prevalence of obesity in children also increased nearly fivefold. Most of these changes occurred after 1978 and happened with dizzying speed. [emaphasis mine]
Note: I’ve partially retracted this comment as indicated by the ETA comments.
I don’t think the quote from Guyenet’s supports SMTM’s argument. Guyenet is merely saying that the trend in extreme obesity has accelerated since 1978. This is consistent with my chart, showing a non-linear (but still quite smooth) line for the 90th percentile in BMI throughout the 20th century.
SMTM says, “Another thing that many people are not aware of is just how abrupt this change was. Between 1890 and 1976, people got a little heavier. The average BMI went from about 23 to about 26. This corresponds with rates of obesity going from about 3% to about 10%. The rate of obesity in most developed countries was steady at around 10% until 1980, when it suddenly began to rise.”
The median person did not merely get “a little heavier”. I think SMTM is misinterpreting the data, and introducing a mystery where one does not really exist. From the chart I showed, the trend in BMIs among average people (say, between say the 20th and 80th percentiles) remained relatively stable over time. There’s neither a hard jump at 1980 nor radical acceleration, though there is some slight acceleration if you squint (and it’s not particularly centered around 1980) [ETA: OK I realized I was being unfair here given that the series stops at around 1986. I’d welcome if someone could find a longer data series. See edit on the other comment too.]. This is also true for the other birth cohorts in the article I cited.
We could do a similar exercise for all sorts of phenomena. Would we say that the Flynn effect began abruptly at some point in the 20th century, simply because a chart showing “percentage of people who are gifted” has a non-linear curve, and picks up speed, say, around 1950? Did economic growth begin abruptly because the percentage of people who are “rich” (defined by some arbitrary cutoff) picked up around 1970?
The abrupt change in obesity is only a strong candidate for a mystery in the sense that it’s not immediately clear why it happened. But once provided the data for BMI over time, it quickly becomes clear that this provides no compelling reason to abandon the palatability theory. [ETA: At least, I have yet to see any compelling reason why the uptick after can’t be explained by slowly rising BMI over the 20th century]
Guyenet, who’s palatability theory you seem to prefer, shares the same interpretation as SMTM. His chart from The Hungry Brain:
And his commentary:
Note: I’ve partially retracted this comment as indicated by the ETA comments.
I don’t think the quote from Guyenet’s supports SMTM’s argument. Guyenet is merely saying that the trend in extreme obesity has accelerated since 1978. This is consistent with my chart, showing a non-linear (but still quite smooth) line for the 90th percentile in BMI throughout the 20th century.
SMTM says, “Another thing that many people are not aware of is just how abrupt this change was. Between 1890 and 1976, people got a little heavier. The average BMI went from about 23 to about 26. This corresponds with rates of obesity going from about 3% to about 10%. The rate of obesity in most developed countries was steady at around 10% until 1980, when it suddenly began to rise.”
The median person did not merely get “a little heavier”. I think SMTM is misinterpreting the data, and introducing a mystery where one does not really exist. From the chart I showed, the trend in BMIs among average people (say, between say the 20th and 80th percentiles) remained relatively stable over time. There’s neither a hard jump at 1980 nor radical acceleration, though there is some slight acceleration if you squint (and it’s not particularly centered around 1980) [ETA: OK I realized I was being unfair here given that the series stops at around 1986. I’d welcome if someone could find a longer data series. See edit on the other comment too.]. This is also true for the other birth cohorts in the article I cited.
We could do a similar exercise for all sorts of phenomena. Would we say that the Flynn effect began abruptly at some point in the 20th century, simply because a chart showing “percentage of people who are gifted” has a non-linear curve, and picks up speed, say, around 1950? Did economic growth begin abruptly because the percentage of people who are “rich” (defined by some arbitrary cutoff) picked up around 1970?
The abrupt change in obesity is only a strong candidate for a mystery in the sense that it’s not immediately clear why it happened. But once provided the data for BMI over time, it quickly becomes clear that this provides no compelling reason to abandon the palatability theory. [ETA: At least, I have yet to see any compelling reason why the uptick after can’t be explained by slowly rising BMI over the 20th century]
See this comment.