Applied Nate Silver – a surprise, but confirmation of a hypothesis

My weigh-in today produced an unexpected (better) result which means my prediction mechanisms just aren’t working as well as I need. That’s the bad news. The good news is that a hypothesis I had, about how I should do exercise, appears to have be proven. So let’s just start with the money graph:


Even though there is little difference I’m still fitting the data with 3rd order polynomial instead of linear because I believe there are underlying reasons to reject linear.

You can see today’s point is right on the long-term trendline and also that last week was a bit of an anomaly, although I don’t really think it is (recall, in my post about the statistical analysis of the scale that each individual reading is ±1.1lbs and even the “consensus” averaging process I use is about ±0.3lbs so the small deviations on this graph are probably not statistically significant (Nate could help me out on this if he’d listen)).

So the result, Δ=-2.6lbs is fine, but it means I still don’t have a good prediction mechanism.

This is now the third week of complete data with the BodyMedia armband sensor and the Activity Manager analysis software. This system requires I track, as best I can, calorie consumption and it tracks calorie expenditure. To compare/calibrate this I have two other sets of data: a) what my exercise machines tell me about calorie burn (just a formula computed from some basic settings of the machine), and, b) a Polar heart rate monitoring system. Now each of my machines has its own heart rate monitor but I was seeing impossibly wide deviations between them for my own sense of “perceived level of effort” (which various articles I’ve found indicate is actually fairly accurate). So this week I used to Polar to “calibrate” my various machines and devise new exercise program based on that finding.

Both from perceived level of effort and the Polar data my elliptical workout is the hardest. I can get closest to my maximum heart rate (standard value would be 154, I’ve hit about 148) and I stay in the aerobic range (and often the “extended” range, >90% max) most of the time. So this week I tried to do intervals (within the programs I use, one of which is called “Interval” by the machine) of either 25% (30 seconds each two minutes) or 16% (20 seconds each two minutes) where I go as hard as I can (my muscles quit before cardiovascular does). So these workouts, while only marginally higher in calories (according the the machine) are much harder for me. And the BodyMedia measured a bit of this, but not all of it.

On my treadmill my issue was that once I got intensity (either through incline or speed, or both) very high, I felt unsteady and was hanging onto the safety bar. The Polar showed me this significantly decreased my heart rate. So going as hard as I could without holding on actually drove up heart rate higher than much higher incline and speed. So that became my workout plan this week. Also I decided to not bother with the “easy” workouts (where my heart rate was < 100) except as brief warmup. Since treadmill has been my most common workout, these changes meant a significant decrease, as computed by the machine, in my workouts, but the change showed as a significant increase as measured by the BodyMedia system.

The stationary bike is my new machine as of the beginning of 2013. I want to use the bike because it’s: a) easier on my aging joints, b) I like biking, and, c) it’s easier to read while on the bike than the other machines and therefore easier to spend time on it. But I could clearly tell that effort on the bike was lower than other machines. But that’s under my control, so using the Polar I was able to determine what I had to do to, at minimum, enter the aerobic range (basically crank > 175 watts on the machine, either through RPMs or resistance level or both). Since I’ve only been using the bike briefly those muscles are very much out of shape and so cranking >175 watts is harder (although getting easier). And as with my real bike it’s actually the RPMs I should kick up (instead of resistance) because that’s easier on my knees.

But the problem with bike, whether my workouts were the “easy” ones I was doing before or the significantly harder ones this week, the BodyMedia basically barely registers the workout. Which leads me to my conclusion that the BodyMedia sensor and software is basically a glorified pedometer (it rates treadmill as more calories than elliptical, even though by measurement and subjective the elliptical is clearly harder). In short it’s counting the acceleration of actual steps (always on treadmill, sometimes on elliptical, almost never on bike) and adjusting those by its measurement of sweating, heat flux, and body temp. I’ve informed BodyMedia about this flaw, but like to many consumer products they don’t listen to customers because they think we’re idiots.

So armed with all this new information I believe this week actually had my hardest workouts since I started this whole program despite the fact that my machines only recorded 7386 calories burned (vs average of 8392 and high of 8620 for preceding three weeks, where my weight loss was less).

Now in the two previous weeks I discovered the “predicted” loss by BodyMedia was off and actually I only achieved about 60%, but this week the prediction was 2.76 which is what I got. So perhaps: a) it is biased toward aggressive exercise, now slow and steady (a big debate in training circles), or, b) this week I managed to avoid any large and difficult-to-measure-calories meals (i.e. restaurant meals). So maybe my calories consumed was more accurate this week, or calories burned was more accurate, or both. As a comparison my alternative method of predicting (from data the machines provide) was 3.04 which overstates the actual, but not that much.

So, what have I learned?

  1. maximizing the portion of my workouts that are “intense” is good
  2. right now the limiting factor on intensity is my muscle tone, not CV, so that means I can improve it further
  3. even if I can’t exactly deduce its relative contribution avoiding “big” meals may be good
  4. I can realistically continue to achieve > 2lbs/week losses for a while longer

So what should I predict for next week? I think this week was better than average so I’m going to ratchet down my prediction (from this week’s actual) and go for Δ1.8 and thus


Achieving this will be a real milestone because it will be the first time since starting this process where I’m down in the range I was when I started training for a triathlon 28 years ago. And if I manage to make it below 200 I’ll be back in a range I haven’t seen for around 35 years so I’m encouraged I can make it.

What’s crazy (and I believe) wrong is that even achieving this level I will still be considering overweight by the “standards”. Now the standards have about 70% of the U.S. as overweight which begins to suggest the standard (which has been lowered) overstates the problem with weight in this country. I actually believe this is true. The fitness nazis who were luckily born with low body mass set themselves as the paragons of excellence and measure everyone else by that standard. The only problem – THEY HAVE NO EVIDENCE to justify their standards. Reading numerous articles from actual scientific journals devoted to metabolism or obesity has shown me how silly much of the nutrition and/or medical “advice” is because it’s based on opinion and dogma and fashion instead of science, but that’s another post.


About dmill96

old fat (but now getting trim and fit) guy, who used to create software in Silicon Valley (almost before it was called that), who used to go backpacking and bicycling and cross-country skiing and now geodashes, drives AWD in Wyoming, takes pictures, and writes long blog posts and does xizquvjyk.
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4 Responses to Applied Nate Silver – a surprise, but confirmation of a hypothesis

  1. dmill96 says:

    At middle of week it’s looking more like 209.5 as the prediction – two bigger than usual meals (losing some resolve to hold back) and a little less exercise today (some interruptions). It’s getting harder and harder to hold to schedule.

  2. dmill96 says:

    209.0, maybe even 209.5, is looking really unlikely. The big meals made at home are hard to estimate calorie intake (sometimes even just actual quantity) but it feels higher than I’m recording. And I’ve really emphasized bike this week, whose calories I have to discount a lot, plus was tired one day and just didn’t do much. Not doing well on Sunday is going to be disheartening and that feeling is getting more and more common, yet I’ve still got such a long way to go.

  3. Pingback: Applied Nate Silver – another (positive) surprise | dailydouq

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