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
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 »
STAFF PICKS
After Wikileaks Hack, DNC Staffers Stared Using ‘Snowden-Approved’ App
5 hours ago
WHY WE CARE

The Signal app is fast becoming the new favorite among those who are obsessed with the security and untraceabilty of their messaging. Just ask the Democratic National Committee. Or Edward Snowden. As Vanity Fair reports, before news ever broke that the DNC's servers had been hacked, word went out among the organization that the word "Trump" should never be used in their emails, lest it attract hackers' attention. Not long after, all Trump-related messages, especially disparaging ones, would need to be encrypted via the Snowden-approved Signal.

Source:
WARRING FACTIONS?
Freedom Caucus Members May Bolt the RSC
8 hours ago
WHY WE CARE

The Republican Study Committee may lose several members of the House Freedom Caucus next year, "potentially creating a split between two influential groups of House conservatives." The Freedom Caucus was founded at the inception of the current Congress by members who felt that the conservative RSC had gotten too cozy with leadership, "and its roughly 40 members have long clashed with the RSC over what tactics to use when pushing for conservative legislation." As many as 20 members may not join the RSC for the new Congress next year.

Source:
SOME THERAPIES ALREADY IN TRIALS
FDA Approves Emergency Zika Test
9 hours ago
THE LATEST

"The U.S. Food and Drug Administration on Monday issued emergency authorization for a Zika diagnostics test from Swiss drugmaker Roche, skirting normal approval channels as the regulator moves to fight the disease's spread." Meanwhile, the Wall Street Journal reports that a new study in Nature identifies "about a dozen substances" that could "suppress the pathogen's replication." Some of them are already in clinical trials.

Source:
MONEY HAS BEEN PAID BACK
Medicare Advantage Plans Overcharged Government
10 hours ago
THE DETAILS

According to 37 newly released audits, "some private Medicare plans overcharged the government for the majority of elderly patients they treated." A number of Medicare Advantage plans overstated "the severity of medical conditions like diabetes and depression." The money has since been paid back, though some plans are appealing the federal audits.

Source:
DESPITE CONSERVATIVE OBJECTIONS
Omnibus Spending Bill Likely Getting a Lame-Duck Vote
10 hours ago
WHY WE CARE

"GOP leaders and House Democrats are already laying the groundwork for a short-term continuing resolution" on the budget this fall "that will set up a vote on a catch-all spending bill right before the holidays." As usual, however, the House Freedom Caucus may throw a wrench in Speaker Paul Ryan's gears. The conservative bloc doesn't appear willing to accept any CR that doesn't fund the government into 2017.

Source:
×