Does the difference matter?

Posted on October 18, 2011


I was listening to a lecture by Stanford professor Robert Sapolsky on human behavior; he was talking about a fascinating study showing that first born children have a higher IQ than their younger siblings. (For those interested in the lecture look up Sapolsky on iTunes University.)

Sapolsky proceeds to ask the class what could explain this difference? Remember these are students at Stanford so they are presumably some pretty smart people. Invariably though student after student proposes a theory and they are shut down.  For example, some students thought that maybe the first born is given extra parental attention, but that was controlled for, or maybe the first born child is given better nutrition, but no, and etc.

Sapolsky keeps pressing and finally a student asks, “What was the difference between the first born and the others?”  “Ahh!” Sapolsky responds.

Then you find out the reason it’s so damn hard to figure out why first born children have a greater IQ than their younger siblings is that because the difference between them is a whopping 2 IQ points. As Sapolsky says, “Somebody could cough next to you, distracting you for a second, thus causing you to score 2 points lower.” In the grand scheme of things the difference doesn’t really matter.

Tying this to fitness: I haven’t heard much about it lately but a few years ago green tea was a hot topic in the supplement world. Companies exalted in it’s ability to help people burn fat as research suggested people who consumed green tea regularly burned more fat than people who did not.

And it’s true, people who consume green tea do burn more fat than people who do not. One of the studies these supplement companies would continually cite showed if you drank 3 cups of green tea per day (a decent amount) you would burn a holy crapload of about 80 more calories per day. 80 calories a day? Who the hell cares about 80 calories a day? For 99% of people, worrying about 80 calories a day is worthless, and probably a sign you’re on the wrong track with your eating.

Another example: The infamous spot-reduction capabilities of things like sit-ups. Guess what? Sit-ups do spot reduce fat around the abdominals. For whatever area you are exercising, if you were to do 30 minutes of continuous activity for that area you would be able to burn at most an extra 2.1 milligrams of fat for that area. To be clear: 30 minutes of non-stop sit-ups will help you burn an extra 2.1 milligrams of fat. (For those interested in more on spot-reduction check this out from Lyle Mcdonald.)

Lastly, be very careful about stats you hear in the media. A common thing heard is something to the effect of “Such and such drug or supplement reduces your risk of such and such disease by such and such percentage.”

You basically can’t infer anything from statements like this and here is why (This example is from the book Worried Sick: A Prescription for Health in an Overtreated America It’s a bit technical but the information is something everyone should be aware of.)

A study on the drug Pravachol found that people who took the drug experienced 29% less fatal heart attacks. So if you were taking Pravachol and had a heart attack you were 29% less likely to die from said heart attack.

Shit, sounds like you want to run to the store and start taking this drug, right? The issue with this is if you look closer at the numbers you see that 6.5% of people who took the drug outlived their heart attack while 4.6% who did not take the drug outlived theirs, a difference of 1.9%.

Where does 29% come from?

Well, 1.9% of 6.5% is 29%. Therefore, if you’re marketing this drug you are going to say that the placebo group experienced a 29% greater chance of dying from an experienced heart attack than the group who took Pravachol. BUT, at the end of the day you are only 1.9% less likely to die from experiencing a heart attack if you do not take the drug.

Here’s another example with made up numbers just to help clarify: Say eating broccoli decreases one’s chances of getting cancer by 50%, and say you and your friend both have a 1% chance of getting cancer but your friend eats a lot of broccoli. Thus, your friend’s chance of getting cancer is .5%, or half of yours. Great…at the end of the day you still only have a 1% chance of getting cancer and your friend only a .5%. (This is also referred to as absolute versus relative risk.)

Find out what the actual difference is before you decide on something. Often times the difference doesn’t matter.


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Posted in: Losing weight