This seems like very little evidence as far as I am concerned.
It claims that eating a higher-fat diet increased cholesterol. This is what I would expect, and I am also entirely unconvinced that this is remotely harmful. They don’t even break up “cholesterol” into the relevant subtypes! Was this an increase in HDL or triglycerides? They rely on a section of the paper to claim that the link between higher cholesterol and cardiovascular mortality is well-established… but then why didn’t they make a study showing increased CVD or all-cause mortality? They have those data as part of the study! I want the body count.
Also, if you look at the correlations they found with increased cholesterol levels, the ones they don’t report in the abstract include “sweet buns and crisp bread rolls, and boiled potato” (as well as boiled coffee and salted fish). So it looks like some kinds of fats and some kinds of carbs correlate with higher cholesterol. That doesn’t seem nearly as compelling as the headline. (Let’s also note that fat consumption as a % of energy only once again reached 1986 levels in 2010, and yet total cholesterol is still significantly lower.)
The continually-rising BMI is more interesting to me. They lowered fat intake, people got fatter. They lowered carb intake, people got fatter. Hmmm… Oddly enough, they don’t report much about total caloric intake—everything is mentioned as a proportion of calories. The shift in fat intake was a fall of 3-4% of calories, then an increase of 3-4% of calories. This would only require a small amount of increased total calories from fat, with no reduction in carb content, to explain the shift as well as the increasing BMI. (Note that they didn’t try to draw any correlations with BMI, because of the well-known bias in food frequency questionnaire reporting.)
What other major food shifts did they note in the study? First of all, potatoes were being replaced with rice and pasta. Second of all, alcohol intake rose continuously over the period in question. I would bet hundreds of dollars that the strongest statistical correlation with BMI would be wine intake, based on the figures they report.
Even as far as associational studies go, this is a really bad one. I mean that seriously, this is methodologically one of the worst I’ve ever seen. I was expecting to actually have my beliefs challenged, a few good associational studies have given me pause, but this is not one of them.
Unfortunately, I feel a little smug about not updating, and Eliezer has pointed out that, to avoid confirmation bias, you should only congratulate yourself when you do update your beliefs. So I’ll try to have LW pick apart the next pro-Atkins study I see too.
This is also a huge epidemiological study that showed lower cholesterol INCREASED risk for death from cardiovascular disease in women. In men, cholesterol and death followed a U-shaped curve, so men with the highest and lowest cholesterol were at increased risk for death. Of course, with the caveat that this is also not a randomized trial and thus not quality evidence, it does call into question whether the increase in cholesterol seen in the 1st study was a good thing or a bad thing.
We have higher quality data from randomized trials that show Statins, which lower cholesterol, don’t reduce mortality when used for primary prevention.
This seems like very little evidence as far as I am concerned.
It claims that eating a higher-fat diet increased cholesterol. This is what I would expect, and I am also entirely unconvinced that this is remotely harmful. They don’t even break up “cholesterol” into the relevant subtypes! Was this an increase in HDL or triglycerides? They rely on a section of the paper to claim that the link between higher cholesterol and cardiovascular mortality is well-established… but then why didn’t they make a study showing increased CVD or all-cause mortality? They have those data as part of the study! I want the body count.
Also, if you look at the correlations they found with increased cholesterol levels, the ones they don’t report in the abstract include “sweet buns and crisp bread rolls, and boiled potato” (as well as boiled coffee and salted fish). So it looks like some kinds of fats and some kinds of carbs correlate with higher cholesterol. That doesn’t seem nearly as compelling as the headline. (Let’s also note that fat consumption as a % of energy only once again reached 1986 levels in 2010, and yet total cholesterol is still significantly lower.)
The continually-rising BMI is more interesting to me. They lowered fat intake, people got fatter. They lowered carb intake, people got fatter. Hmmm… Oddly enough, they don’t report much about total caloric intake—everything is mentioned as a proportion of calories. The shift in fat intake was a fall of 3-4% of calories, then an increase of 3-4% of calories. This would only require a small amount of increased total calories from fat, with no reduction in carb content, to explain the shift as well as the increasing BMI. (Note that they didn’t try to draw any correlations with BMI, because of the well-known bias in food frequency questionnaire reporting.)
What other major food shifts did they note in the study? First of all, potatoes were being replaced with rice and pasta. Second of all, alcohol intake rose continuously over the period in question. I would bet hundreds of dollars that the strongest statistical correlation with BMI would be wine intake, based on the figures they report.
Even as far as associational studies go, this is a really bad one. I mean that seriously, this is methodologically one of the worst I’ve ever seen. I was expecting to actually have my beliefs challenged, a few good associational studies have given me pause, but this is not one of them.
Thanks! I’ll go ahead and not update.
Unfortunately, I feel a little smug about not updating, and Eliezer has pointed out that, to avoid confirmation bias, you should only congratulate yourself when you do update your beliefs. So I’ll try to have LW pick apart the next pro-Atkins study I see too.
This is also a huge epidemiological study that showed lower cholesterol INCREASED risk for death from cardiovascular disease in women. In men, cholesterol and death followed a U-shaped curve, so men with the highest and lowest cholesterol were at increased risk for death. Of course, with the caveat that this is also not a randomized trial and thus not quality evidence, it does call into question whether the increase in cholesterol seen in the 1st study was a good thing or a bad thing.
We have higher quality data from randomized trials that show Statins, which lower cholesterol, don’t reduce mortality when used for primary prevention.