<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>gwern</author><text>Fulltext: &lt;a href=&quot;https://www.dropbox.com/s/gfch760k1ratwo3/2015-rottensteiner.pdf&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.dropbox.com&amp;#x2F;s&amp;#x2F;gfch760k1ratwo3&amp;#x2F;2015-rottensteiner...&lt;/a&gt; &amp;#x2F; &lt;a href=&quot;http://sci-hub.org/downloads/045f/10.0000@pdfs.journals.lww.com@generic-FD16BBD9129B.pdf&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;sci-hub.org&amp;#x2F;downloads&amp;#x2F;045f&amp;#x2F;10.0000@pdfs.journals.lww....&lt;/a&gt;&lt;p&gt;Buried some interesting points there:&lt;p&gt;&amp;gt; The researchers were looking for young adult identical twins in their early- to mid-20s whose exercise habits had substantially diverged after they had left their childhood homes. These twins were not easy to find. Most of the pairs had maintained remarkably similar exercise routines, despite living apart.&lt;p&gt;Besides the testament to how &amp;#x27;everything is heritable&amp;#x27; inherent in that observation, it also raises the question: if they are so unusual, doesn&amp;#x27;t that make confounding more plausible?&lt;p&gt;&amp;gt; Interestingly, the twins tended to have very similar diets, whatever their workout routines, so food choices were unlikely to have contributed to health differences.&lt;p&gt;Also very interesting, and counter to the usual narratives about health. (Everything is heritable...)&lt;p&gt;&amp;gt; The twins’ brains also were unalike. The active twins had significantly more grey matter than the sedentary twins, especially in areas of the brain involved in motor control and coordination.&lt;p&gt;Warning sign: &amp;#x27;significantly&amp;#x27;. Does this mean, as any ordinary person would take it to mean (in conjunction with that lazy stock photo), &amp;#x27;a lot&amp;#x27; or does it mean &amp;#x27;p&amp;lt;0.05&amp;#x27;?&lt;p&gt;Trick question, of &lt;i&gt;course&lt;/i&gt; it means the latter, which is useless! Take a look at the fulltext, pg6, table 2, which spits out the &lt;i&gt;actual&lt;/i&gt; differences between the twin pairs. I hope you&amp;#x27;re ready to be wowed by how much difference an exercise regimen makes when you control for genetics (picking out a few I recognize):&lt;p&gt;1. BMI: -0.8&lt;p&gt;2. VO2max: 6.3&lt;p&gt;3. weight: -2kg&lt;p&gt;4. waist circumference: -3.3cm&lt;p&gt;5. fat percentage: -3.3 (!)&lt;p&gt;6. lean mass: 1.4kg&lt;p&gt;I&amp;#x27;m not sure I&amp;#x27;ve seen such a damning indictment of exercise in a long time. (Less than 1 on BMI? 2kg of weight? I fluctuate more than that on a weekly basis...)</text><parent_chain></parent_chain></comment><story><title>One Twin Exercises, the Other Doesn’t</title><url>http://well.blogs.nytimes.com/2015/03/04/one-twin-exercises-the-other-doesnt/</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>AstroChimpHam</author><text>&amp;gt;But eventually the researchers homed in on 10 pairs of male identical twins, one of whom regularly exercised, while the other did not, usually because of work or family pressures, the researchers determined.&lt;p&gt;That &amp;quot;work and family pressure&amp;quot; sounds like stress and a pretty important confounding variable.</text><parent_chain></parent_chain></comment><story><title>One Twin Exercises, the Other Doesn’t</title><url>http://well.blogs.nytimes.com/2015/03/04/one-twin-exercises-the-other-doesnt/</url></story>