For those of you who don't know me, I'm Granola. I'm bulimic and have been for the past years. I've been eating disordered for about 8 years. I tried to explain the information that I'm about the present in another community, but I don't think the audience was, uh, receptive enough. I'm not trying to beat a dead horse into the ground, but I looked around and didn't see it posted yet.
I'm not an advocate of purging in the least. Unless you're a big fan or heartburn or tooth decay, I don't really see a reason why anyone would want to do it. However, I'm also not an advocate of misinformation. Those who know me know that I'm extremely tired of this particular piece of information:
"Contrary to popular belief, purging isn’t very effective at getting rid of calories, which is why most bulimics end up gaining weight over time. Vomiting immediately after eating will only eliminate 50% of the calories consumed at best—and usually much less. This is because calorie absorption begins the moment you put food in the mouth." - Some credible health website
As most of you know, this piece of information is based on a scientific study. Many of you have probably seen the abstract:
" While caloric consumption during binge eating has been measured, it is not known how many of the calories are retained in the gastrointestinal tract after vomiting. In 17 normal weight bulimic patients, there appeared to be a ceiling on the number of calories retained after vomiting. That is, whether or not bulimic patients had small (mean = 1,549 kcal, SD = 505) or large (mean = 3,530 kcal, SD = 438) binges, they retained similar amounts of kilocalories (mean = 1,128, SD = 497, versus mean = 1,209, SD = 574, respectively) after vomiting."
Those who have taken any sort of research-based class know that you cannot judge an entire study based on it's abstract. When we were in our experimental Psych class, our teacher had us print out and turn in entire articles to make sure that we weren't writing research papers using only an abstract. I'd like to take the time to do a critical analysis on the entire article in order to point out the shortcomings and confounding factors as well as debunk the myth, which was spawned solely from this study, that you retain more than half of the calories from purging.
Without further ado:
I've made jpeg files from a PDF file. Notice my tremendous MSPaint skills. If anyone can't stand the cutting and pasting and wants the PDF file just message me. Beware, this is a long boring post.
From just reading the abstract one could conclude that:
-This study was done back in 1993. What was I doing in 1993? I think I was getting picked last for kickball. I was only eating one items from my lunch tray and I had no boobs.
- Whether they had small or large binges, half of the calories were retained by the subjects following purging.
- This is a 'brief report'. The writers explain why this is a 'brief report' later as opposed to a full study.
Moving along to the Introduction and the all important Methods:
The Intro is fine. The report is brief so the Intro doesn't need to be long. Read it. It's interesting.
The Method is so full of shit that I don't know where to begin.
-17 subjects. For most experiments you must use at least 30 subjects. This study is using 17. 17 out of the thousand of people with bulimia. 17 people in Pittsburgh.
-Only normal weight bulimics were used. That's understandable because they have to control for weight. No one under 85% bodyweight. That means no B/P anorexics allowed. There's a lot I can say about this, but I'll leave it alone so that no gets mad.
- 3 patients were IP patients, 12 were about to start OP, and 2 were already in OP. The 12 about the start OP had just finished another feeding experiment the day before! Can we say fatigue?
- The study began at 8:00am after an overnight fast. It's in a 'feeding laboratory'. Not a little hotel room. Not a simulated bedroom or kitchen. I'm thinking a cafeteria full of bulimics.
-There's a vending from which the bulimics must select their food. A computer records the selection. They are then instructed to vomit into their own bucket. After they finished vomiting, they are asked to wait an hour and not eat any food. The experimenters didn't even control for the type of food binged on. What if one girl chooses chocolate poptarts and another chooses ice cream? Who do you think is going to have the easier time purging? I
-The amount of calories in the vomitus is measured.
Look at those standard deviations!!! How do you even get a study published looking like that?
-Just the Graphs: One of these girls ate a little over 2000cals and vomited a little over 2000 cals. Another ate almsot 6,000cals (damn, leave some for everyone else) and purged a little over 3,000. At least two people 'binged' on less than 500 cals and therefore purged less than 500 cals. Someone binged on 1200 cals and didn't even bother to purge. And a bunch of people who binged on less than 2200 cals didn't even purge 500 cals. These girls were all over the place. I wonder what was going on? A movie? Foods that they didn't like?
-Just the Results: The girls ranged in age from 14 to 30. Average body weight was 85% to 126% of IBW. They binged form 3 to 30 times a week and vomited from 3 to 40 times a week.
The SD is ridiculous: using two SD above and below the mean, between 0 and 4433 calories were consumed and between 0 and 2985 cals were vomited by the 96% of the girls. Uh... what? There's too much of a gap between the highest bingers and the ones who ate less then 500 cals. Twelve of the binges were fewer than 2110 cals. Then twelves of the binges probably weren't even binges.
If someone else wants to tear into these stats be my guest. There's nothing significant about them.
The researchers admit they they had several problems with the study:
-Most significant I think is the fact that the bulimic didn't reliably notify the experimenters when they needed to vomit. I'm assuming that some of them were scared, embarrassed, or even indifferent. Whenever I'm binging and I don't get a chance to purge, I usually give up.
-The bulimics were distracted and didn't follow instructions easily.
-The experiment was supposed to last for 24 hours, but it had to be cut short. That could be why this article is so short.
-The writer concludes that vomiting is an effective means of ridding the body of calories, particularly for large binges.
-The writers try to cover up for their bullshit results by making up something about calorie absorption.
And that's the end of my analysis. When health sites and textbooks quote this study, they are only looking at the results presented in the abstract. Unless you look at the whole study, there's no way that you can get the whole picture. The fact that the study is so flawed and still continues to be quoted angers me. I don't like it when sciences is twisted to support someone else's agenda.
Rant over. Comments will be appreciated.
Sorry I'm so long-winded. And sorry for any typos. I'm sure there's many.