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
Add to Briefcase
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 »
PASSAGE NOT GUARANTEED
House Freedom Caucus Endorses Obamacare Replacement
26 minutes ago
BREAKING

After more than a month of back and forth, a failed bill, and GOP embarrassment, the ultra-conservative House Freedom Caucus has announced that it will support the Obamacare replacement legislation in its most recent iteration. Rep. Mark Meadows, the chairman of the caucus, said the roughly 30 members of the caucus view this compromise as the best option short of a full repeal. A recent amendment, authored by Meadows and Rep. Tom McArthur, co-chair of the more moderate Tuesday Group, would allow states to apply for waivers exempting them from provisions forbidding insurers from charging higher prices to those with pre-existing conditions if the state set up a high-risk pool. The plan's passage in the House is not a done deal though, as a number of moderate lawmakers have resisted supporting the amendment.

COULD RATTLE MARKETS
White House Working On Order To Leave NATO
1 hours ago
BREAKING
IRANIANS CAME WITHIN 1,000 METERS
U.S. Navy Vessel Fired Flare at Iranian Boat on Monday
2 hours ago
THE DETAILS

"A U.S. Navy guided-missile destroyer fired a warning flare toward an Iranian Revolutionary Guard vessel coming near it in the Persian Gulf. The incident happened Monday as the vessel closed to within 1,000 meters of the USS Mahan, "despite the destroyer trying to turn away from it." After attempting to contact the Iranian vessel and sounding its whistle, it deployed the flare. After that, the ship had had enough and turned away.

Source:
ON SANCTUARY CITIES
White House Attacks Judge Who Suspended Executive Order
2 hours ago
THE DETAILS

U.S. District Judge William Orrick Tuesday blocked the Trump administration from enforcing part of an executive order calling for the end of federal funding to so-called sanctuary cities. The decision was followed by a scathing rebuke from the White House, a precedent-breaking activity which with this White House has had no qualms. A White House statement called the decision an "egregious overreach by a single, unelected district judge." The statement was followed by an inaccurate Wednesday morning tweetstorm from Trump, which railed against the Court of Appeals for the Ninth Circuit. While Judge Orrick's district falls within the jurisdiction of the Ninth Circuit, Orrick himself does not serve on the Ninth Circuit.

MAY BRING CONSERVATIVES ON BOARD, BUT WHAT ABOUT MODERATES?
House GOP Circulates Amendment on Preexisting Conditions
5 hours ago
THE LATEST

"House Republicans are circulating the text of an amendment to their ObamaCare replacement bill that they believe could bring many conservatives on board. According to legislative text of the amendment," drafted by Rep. Tom MacArthur (R-NJ), "the measure would allow states to apply for waivers to repeal one of ObamaCare’s core protections for people with pre-existing conditions. Conservatives argue the provision drives up premiums for healthy people, but Democrats—and many more moderate Republicans—warn it would spark a return to the days when insurance companies could charge sick people exorbitantly high premiums."

×
×

Welcome to National Journal!

You are currently accessing National Journal from IP access. Please login to access this feature. If you have any questions, please contact your Dedicated Advisor.

Login