Showing posts with label dieting. Show all posts
Showing posts with label dieting. Show all posts

Clever food hacks from Cornell Food Lab might all be fake

Have you heard that serving your food on smaller plates will make you eat less? I know I have. I even bought smaller plates for our kitchen when I first heard about that study, which was published in 2011.

And did you know that men eat more when other people are watching? Women, though, behave exactly the opposite: they eat about 1/3 less when spectators are present. Perhaps guys should eat alone if they're trying to lose weight.

Or how about this nifty idea: kids will eat more fruits and vegetables at school if the cafeteria labels them with cool-sounding names, like "x-ray vision carrots." Sounds like a great way to get kids to eat healthier foods.

Or this: you'll eat less if you serve food on plates that are different colors from the food. If the plate is the same color, the food blends in and it looks like you've got less on your plate.

And be sure to keep a bowl of fruit on your counter, because people who do that have lower BMIs.

Hang on a minute. All of the tips I just described might be wrong. The studies that support these clever-sounding food hacks all come from Cornell scientist Brian Wansink, whose research has come under withering criticism over the past year.

Wansink is a professor at Cornell University's College of Business, where he runs the Food and Brand Lab. Wansink has become famous for his "kitchen hacks" and healthy-eating tips, which have been featured on numerous media outlets, including the Rachel Ray show, Buzzfeed, USA Today, Mother Jones, and more.

Last week, Stephanie Lee at Buzzfeed wrote a lengthy exposé of Wansink's work, based on published critiques as well as internal emails that Buzzfeed obtained through a FOIA request. She called his work "bogus food science" and pointed out that
"a $22 million federally funded program that pushes healthy-eating strategies in almost 30,000 schools, is partly based on studies that contained flawed — or even missing — data."
Let's look at some of the clever food hacks I described at the top of this article. That study about labeling food with attractive names like "x-ray vision carrots"? Just last week, it was retracted and replaced by JAMA Pediatrics because of multiple serious problems with the data reporting and the statistical analysis.

The replacement supposedly fixes the problems. But wait a second: just a few days after that appeared, scientist Nick Brown went through it and found even more problems, including data that doesn't match what the (revised) methods describe and duplicated data.

How about the studies that showed people eat more food when others are watching? One of them, which found that men ate more pizza when women were watching, came under scrutiny after Wansink himself wrote a blog post describing his methods. Basically, when the data didn't support his initial hypothesis, he told his student to go back and try another idea, and then another, and another–until something comes up positive.

This is a classic example of p-hacking, or HARKing (hypothesizing after results are known), and it's a big no-no. Statistician Andrew Gelman took notice of this, and after looking at four of Wansink's papers, concluded:
"Brian Wansink refuses to let failure be an option. If he has cool data, he keeps going at it until he finds something, then he publishes, publishes, publishes."
Ouch. That is not a compliment.

Soon after Gelman's piece, scientists Jordan Anaya, Tim van der Zee, and Nick Brown examined four of the Wansink's papers and found 150 inconsistencies, which they published in July, in a paper titled "Statistical Heartburn: An attempt to digest four pizza publications from the Cornell Food and Brand Lab." Anaya subsequently found errors in 6 more of Wansink's papers.

It doesn't stop there. In a new preprint called "Statistical infarction," Anaya, van der Zee and Brown say they've now found problems with 45 papers from Wansink's lab. Their preprint gives all the details.

New York Magazine's Jesse Singal, who called Wansink's work "really shoddy research," concluded that
"Until Wansink can explain exactly what happened, no one should trust anything that comes out of his lab."
In response to these and other stories, Cornell University issued a statement in April about Wansink's work, saying they had investigated and concluded this was "not scientific misconduct," but that Cornell had "established a process in which Professor Wansink would engage external statistical experts" to review many of the papers that appeared to have flaws.

And there's more. Retraction Watch lists 14 papers of Wansink's that were either retracted or had other notices of concern. Most scientists spend their entire careers without a single retraction. One retraction can be explained, and maybe two or even three, but 14? That's a huge credibility problem: I wouldn't trust any paper coming out of a lab with a record like that.

But how about those clever-seeming food ideas I listed at the top of this article? They all sound plausible–and they might all be true. The problem is that the science supporting them is deeply flawed, so we just don't know.

Finally, an important note: Brian Wansink is a Professor of Marketing (not science) in Cornell's College of Business. He is not associated with Cornell's outstanding Food Science Department, and I don't think his sloppy methods should reflect upon their work. I can only imagine what the faculty in that department think about all this.

Is being a little bit obese unhealthy?

Everyone knows that being obese is very bad for your health. But how overweight do you have to be before you should worry? A new study covering millions of people attempts to answer this question.

The short answer: being a little bit fat isn't so bad, especially if you're already a senior citizen, but the fatter you are, the shorter your life expectancy. Let's dive into the details.

The new study, published in The Lancet, is a combined evaluation (a meta-analysis) of 239 studies that included over 10 million people from four continents: Asia, Australia, Europe and North America. All the studies followed their subjects for a long time, averaging nearly 14 years of observation. The authors (a large consortium called "The Global BMI Mortality Collaboration") wanted to exclude people who might have already been sick, so their study only looked at people who (a) had never smoked, and (b) who lived at least five years after the study began.

This left them with nearly 4 million people, of whom 385,879 died at some time during the course of the study. From this large data set, the researchers computed the risk of death as a function of body mass index (BMI).

[Aside: BMI is a simple function of your height and weight. For example, someone who stands 5'11" and weights 170 has a BMI of 23.7. A height of 5'6" and weight of 150 gets you a BMI of 24.2. You can calculate your own BMI using this calculator.]

The study divided people into six groups:

  • underweight, BMI 15–18.5
  • normal, BMI 18.5–24.9
  • overweight, BMI 25–29.9
  • obesity grade 1, BMI 30–34.9
  • obesity grade 2, BMI 35–39.9
  • obesity grade 3, BMI 40 or above

The main outcome that they studied was mortality (death) from any cause. Of course, one can argue that this is too simplistic, since if someone dies from, say, an auto accident, it probably wasn't due to their weight. But the results were consistent across all four continents, which argues that the study design was probably good. Here are the main findings for each group:
  • BMI 15–18.5: 47% increased risk of death
  • BMI 18.5–24.9: no increase (normal)
  • BMI 25–29.9: 11% increased risk of death
  • BMI 30–34.9: 44% increased risk of death
  • BMI 35–39.9: 92% increased risk of death
  • BMI 40 or above: 171% increased risk of death
Another way to describe these hazard ratios is this: with a BMI above 40, people are 2.71 times as likely to die during any particular time period as people with a normal BMI. 

If these numbers seem scary, keep in mind that this is relative risk, not absolute risk. So an 11% increase in risk might mean that your chance of dying increases from 1% to 1.11%; it certainly doesn't mean you have an 11% risk of dying. 

To put some real numbers on this risk, consider this comparison: out of 1,075,894 people with a near-optimal BMI between 22.5–25.0, 98,833 died during the course of the study, or 9.2%. (Remember that these data come from 239 different studies, and the average length of followup is 14 years. So fewer than 1% of this group died per year.) Compare this group to people with obesity grade 1, or BMI from 30–35. That group had 330,840 people, of whom 37,318 died, or 11.3%. After various adjustments, this translates into a 44% relative increase, but the actual mortality rate, per year, was about 0.66% versus 0.81% in the two groups.

One mildly positive note: if you're already 70 or older, having a BMI from 25–30 has almost no effect; in other words, it's okay to be a little plump when you're older.

A word of warning to men: the ill effects of obesity are much stronger in men than in women. The study breaks down those hazard ratios by sex, and in each range the risk is higher for men than for women. So for example, if you're a woman with a BMI of 30–35, your hazard ratio is 1.37 (37% higher risk of death), but for men it is 1.70 (70% increase). 

There are many, many more details in the study, including a breakdown of how BMI is associated with four major causes of death (heart disease, cancer, respiratory disease, and stroke), and if you're interested in those, you should read the study

Of course, one can think of many caveats to these findings: people die from all sorts of illnesses, and many of them are not caused by being overweight. For any individual case, we might not be able to say whether someone's weight had anything to do with their illness. Nonetheless, this very large study shows clearly that the more obese you are, the greater your risk of dying. That's precisely what we would expect if obesity was causally linked to mortality.

So is it okay to be a little bit fat? The answer is probably yes: people with a BMI of 25 might view themselves as "a bit" fat, even though they are not overweight. But very high BMIs (and very low BMI, below 18.5) are definitely unhealthy. Unfortunately, no one has an easy answer to the problem of losing weight (despite what you might have heard from Dr. Oz), but if you do have a dangerously high BMI, reducing it will likely be good for your health.