I was driving around in my car yesterday, minding my own business, when a story came onto my local NPR station that caught my attention. Kevin Hall PhD was on the air talking about his new study comparing how the body responds to low fat vs. low carb diets. He was careful to state that the study compared people in carefully controlled environments as opposed to relying on food journals for information on food journals (because you KNOW us fat folks can’t be counted on to be honest about those things). He said that the study participants were brought in for two, two-week inpatient hospital stays where every morsel of food was accounted for. In fact, every person was fed the exact same breakfast, lunch and dinner every day for two weeks, were expected to eat all of it and were not allowed to have anything different. (I think the study creators took their lives into their hands with this one, because if you fed me the exact same, low-calorie, diet crud for two weeks running, I’m quite sure I’d become pretty stabby. And I don’t know what could possibly compel me to return for the second phase of that torturous crud. But I digress.)
Kevin said all of the subjects “had obesity” which is a funny, disease-language sort of way to say they were fat. But none of them had diabetes. And according to Kevin, the study indicated that at a metabolic level there was very little difference in weight loss results from the low fat vs. the low carb diets. Although, the low carb diet had a greater impact on blood glucose levels than the low fat diet. And the low fat diet apparently led to slightly greater fat loss within the two week period than the low carb diet. Okay. Got it.
But then the report started to go off the rails for me. Kevin suggested that based on this study we could extrapolate that the low-fat diet would lead to greater weight loss over the long term than the low-carb diet. And that’s when I had to pull the car over because I was shouting at the radio.
“How can you extrapolate anything over the long term other than the notion that most of these people won’t keep the weight off or will even gain weight after this experiment,” I said. “This study has a lot to do with metabolism but you can’t really expect to transfer the results of this study to real life!” I tried to call in to express my opinion, but by time I got through the story was over. So I resolved to hit the radio station website, find the study and take a look for myself.
I did just that. And the data extrapolation situation was so much worse than I thought. The study contained a grand total of 19 subjects. During the first two-week stay, the subjects ate a eucaloric baseline diet for 5 days, followed by 6 days on either a reduced fat diet or a reduced carbohydrate diet. Then there was a 2-4 week “washout period” when they went home. After that, they returned and ate the eucaloric baseline diet for 5 days followed by a reduced fat or reduced carbohydrate diet. Each subject switched diets for the second two week stretch. So if they did the low fat diet in the first stretch, they did the low carb diet in the second stretch and vice versa.
Okay. So there’s some good stuff here. The study carefully tries to control for various factors. The food is the same each day, so there won’t be wild fluctuations there. All subjects are, um, subjected to both diets so that helps eliminate some of the variables. And everybody eats exactly the same thing. Subjects spent a significant amount of time in a metabolic chamber to very carefully measure the way the calories were metabolized. I see the point of needing this level of precision to control the variables of the experiment.
But my big, BIG problem came during the radio interview when Kevin started talking about how this could apply to real world fatties and what it would mean for them. He suggested that over the long term (so far the study doesn’t even have 6 months worth of follow up data) the minute differences in weight loss from the two diets would accumulate and you would see significantly greater weight loss from the low-fat diet vs. the low carb diet. This despite the overwhelming evidence outside of this study that indicates that over the true long term (2-5 years) the most likely outcome for the vast majority of the subjects is either insignificant weight loss or even weight gain.
Don’t get me wrong, I love it when science people are science-ing. But when you extrapolate from 19 subjects over 22 days in an extremely controlled environment that is virtually impossible to replicate in the real world to what effect these diets will have over the long term in the real world, I’ve got a serious problem with that. I have talked about it before, and I will talk about it again. If you want to understand science, possibly the last thing on earth you should do is listen to science reporting in the mainstream media.
And I have to wonder about the millions of people who are going to hear this report and hop on the diet/shame/regain cycle all over again because science people say they should. Because when you take science and simplify and stretch it beyond all limits in order to get a popular news story to help bump up your funding, you are behaving irresponsibly and people, especially fat people will wind up getting hurt.
Jeanette DePatie (AKA The Fat Chick)
P.S. Want me to come and sort out some science reporting for your group? Click here to learn more about hiring me as a speaker!