Everything We Know About Nutrition May Be Wrong

A new study says 40 years of CDC data connecting food and obesity are fundamentally flawed.

National Journal
Brian Resnick
See more stories about...
Brian Resnick
Oct. 10, 2013, 7:52 a.m.

For 40 years, the Cen­ters for Dis­ease Con­trol and Pre­ven­tion has been ask­ing people what they eat in an at­tempt to un­der­stand the con­nec­tions between what we con­sume and how our bod­ies feel. And for 40 years, they may have been do­ing it wrong.

The lim­it­a­tions of the CDC data “make it ex­ceed­ingly dif­fi­cult to dis­cern tem­por­al pat­terns in cal­or­ic in­take that can be re­lated to changes in pop­u­la­tion rates of obesity.”

That’s the claim in a new study pub­lished in the on­line journ­al PLO­Sone. The re­search­ers probe CDC’s Na­tion­al Health and Nu­tri­tion Ex­am­in­a­tion Sur­vey, which has in­ter­viewed Amer­ic­ans about the foods they eat and their life­styles since 1971. From the sur­vey, we learned things about nu­tri­tion that now seem so fun­da­ment­al — that diet and ex­er­cise choices are linked to body weight, that cho­les­ter­ol is linked to heart dis­ease, and so on.

But here’s the prob­lem, ac­cord­ing to the au­thors: All of that data was com­piled by ask­ing people to re­call what they ate.

“Nu­tri­tion sur­veys fre­quently re­port a range of en­ergy in­takes that are not rep­res­ent­at­ive of the re­spond­ents’ ha­bitu­al in­takes,” the au­thors write. “And es­tim­ates of EI [en­ergy in­take] that are physiolo­gic­ally im­plaus­ible (i.e., in­com­pat­ible with sur­viv­al) have been demon­strated to be wide­spread.” Men and wo­men have been found to un­der­re­port cal­or­ies by between 12 per­cent and 20 per­cent, and are more likely to se­lect­ively un­der­re­port eat­ing the bad stuff, such as fat and sug­ar.

Trans­la­tion: We can’t trust hu­man memory as the source of our nu­tri­tion data, be­cause people can un­der­re­port what they eat to an ab­surd de­gree. Their self-re­ports doc­u­mented amounts of food that could not pos­sibly sup­port their sur­viv­al. “In no sur­vey did at least 50 per­cent of the re­spond­ents re­port plaus­ible EI [en­ergy in­take] val­ues,” the au­thors re­port.

The NHANES sur­vey does con­tain many, many ob­ject­ive meas­ures such as phys­ic­al ex­am­in­a­tions and blood work (for in­stance, it found el­ev­ated levels of lead in Amer­ic­ans’ blood work, which lead to the de­creased use of the met­al in gas­ol­ine and soda cans). But it’s not like the CDC can mon­it­or all a per­son eats. Nor is it really feas­able to do large-scale ex­per­i­ments on nu­tri­tion — that is, sep­ar­ate people in­to con­trol and ex­per­i­ment­al groups, have every­one eat the same ex­act things ex­cept for one vari­able, and then com­pile this data over dec­ades.

Gran­ted, in re­cent years, CDC has re­vised i’ts meth­od­o­logy. Since 2001, it has fol­ded NHANES in­to the “What We Eat in Amer­ica Pro­gram, which re­cords food in­take in a more con­trolled man­ner.

But there’s even reas­on to be­lieve that as time went on, and as the sur­vey raised aware­ness of obesity, people’s an­swers be­came even more skewed. The au­thors ex­plain:

“There is strong evid­ence that the re­port­ing of ‘so­cially un­desir­able’ (e.g., high fat and/or high sug­ar) foods has changed as the pre­val­ence of obesity has in­creased. Ad­di­tion­ally, re­search has demon­strated that in­ter­ven­tions em­phas­iz­ing the im­port­ance of ‘healthy’ be­ha­vi­ors may lead to in­creased mis­re­port­ing as par­ti­cipants al­ter their re­ports to re­flect the ad­op­tion of the ‘health­i­er’ be­ha­vi­ors in­de­pend­ent of ac­tu­al be­ha­vi­or change.”

The sur­vey in­dic­ates that health be­ha­vi­or in­flu­ences re­sponses to fu­ture sur­veys. And that’s bad sci­ence. All in all, the au­thors con­clude that the lim­it­a­tions of the NHANES data “make it ex­ceed­ingly dif­fi­cult to dis­cern tem­por­al pat­terns in cal­or­ic in­take that can be re­lated to changes in pop­u­la­tion rates of obesity.”

It doesn’t mean our nu­tri­tion as­sump­tions are wrong. It just means we haven’t proven them, be­cause our meth­ods have been flawed.

What We're Following See More »
BACKING OUT ON BERNIE
Trump Won’t Debate Sanders After All
1 days ago
THE LATEST

Trump, in a statement: “Based on the fact that the Democratic nominating process is totally rigged and Crooked Hillary Clinton and Deborah Wasserman Schultz will not allow Bernie Sanders to win, and now that I am the presumptive Republican nominee, it seems inappropriate that I would debate the second place finisher. ... I will wait to debate the first place finisher in the Democratic Party, probably Crooked Hillary Clinton, or whoever it may be.”

AKNOWLEDGING THE INEVITABLE
UAW: Time to Unite Behind Hillary
2 days ago
THE DETAILS

"It's about time for unity," said UAW President Dennis Williams. "We're endorsing Hillary Clinton. She's gotten 3 million more votes than Bernie, a million more votes than Donald Trump. She's our nominee." He called Sanders "a great friend of the UAW" while saying Trump "does not support the economic security of UAW families." Some 28 percent of UAW members indicated their support for Trump in an internal survey.

Source:
AP KEEPING COUNT
Trump Clinches Enough Delegates for the Nomination
2 days ago
THE LATEST

"Donald Trump on Thursday reached the number of delegates needed to clinch the Republican nomination for president, completing an unlikely rise that has upended the political landscape and sets the stage for a bitter fall campaign. Trump was put over the top in the Associated Press delegate count by a small number of the party's unbound delegates who told the AP they would support him at the convention."

Source:
TRUMP FLOATED IDEA ON JIMMY KIMMEL’S SHOW
Trump/Sanders Debate Before California Primary?
2 days ago
THE LATEST
CAMPAIGNS INJECTED NEW AD MONEY
California: It’s Not Over Yet
2 days ago
THE LATEST

"Clinton and Bernie Sanders "are now devoting additional money to television advertising. A day after Sanders announced a new ad buy of less than $2 million in the state, Clinton announced her own television campaign. Ads featuring actor Morgan Freeman as well as labor leader and civil rights activist Dolores Huerta will air beginning on Fridayin Fresno, Sacramento, and Los Angeles media markets. Some ads will also target Latino voters and Asian American voters. The total value of the buy is about six figures according to the Clinton campaign." Meanwhile, a new poll shows Sanders within the margin of error, trailing Clinton 44%-46%.

Source:
×