Musings on Exercise and Diet

Musings on Exercise and Diet 

Wednesday, September 07, 2011 

It seems to me that the SparkPeople site tries to do two different things with the fitness tracker and exercise, and the two are not always totally compatible. 

First, the fitness tracker is a motivational tool to get me to actually DO some exercise. So far, it works quite well for that purpose. 

Second, the fitness tracker wants me to adjust my fitness goals, which are used to feed the nutrition tracker's calorie range goal. (And maybe macronutrient range goals as well?) I don't know all the details of how the nutrition tracker calculates the goal ranges; but it's pretty clear that if I tell the fitness tracker I'm going to burn 700 more calories per week, the nutrition tracker will tell me to eat 100 more calories per day. 

Some time ago, I made the decision that I would use the fitness tracker primarily for its motivational purpose. I no longer debate whether one set of 5 TGU/Windmill combos on each side is "worth" a Spark Point. I use the tracker to track them, and it gets me to do them. Good enough. On the cardio side, I use the fitness tracker to record intentional exercise. That is, if I go for a walk and the major purpose is to be moving, I record it. If I go for a walk to get someplace, or to stroll and enjoy the weather, I don't. I don't count mowing the lawn, because I don't need the SP motivational push to get that done. (Though the past weekend's result might imply a bit of denial in that last sentence.) 

Since I'm firmly committed to using the fitness tracker primarily as a motivational tool, that puts me in an uncertain position with respect to measuring calories burned and determining nutritional target ranges. If I understand the instructions correctly, I'm supposed to count cardio as stuff that puts my heart rate at 60% to 85% of the maximum. But that's not my guideline for motivational tracking. A walk at 4 mph might put my heart rate at 54% of the max, which falls short of "exercise" by the cardio definition; I don't know how many fewer calories I burn because I'm below target heart range. 

I also have a problem with the calorie estimates. Cycling at 13 mph calculates out to almost twice as many calories as walking at 4.2 mph for the same length of time. But my perceived rate of exertion is much lower for the cycling. At least one of those calculations has to be wrong. In practice, I've cycled a lot less since starting SP. Part of this is not wanting cycling to artificially pump up the calorie burn count, and part is wanting to get steps for the pedometer. (That stupid 10K steps per day motivational trick, y'know.) 

Then there's strength training. The fitness tracker gives me no calories burned for lifting weights. There is probably no good way to approximate calories burned by strength training; the variables involved make the cycling/walking comparison look simple. But I know that lifting weights can burn a lot of calories, even if it isn't cardio. In 2005, strength training alone was sufficient to take me from very slow weight loss to a defined downward weight trend as I increased my strength. 

All this comes together with other random information to create a large uncertainty in my mind. I dropped 16 pounds in my first 7 weeks on SP. That's 2.2 pounds per week. With a goal of losing 21 pounds from where I started with the site, it's recommended that I lose a half pound to a pound a week. I've read a rule of thumb that the maximum fat you can lose is 1% of your body weight per week. If I'm under 200 pounds, losing more than 2 pounds per week would then imply I'm losing more than fat. 

On the one hand, it looks like I'm losing faster than I ought to this close to goal. On the other hand, I'm clearly becoming more fit. I'm running longer periods, my resting heart rate is going down, and I'm lifting more weight without aching as badly the next day. Then there's the transition to maintenance. I suspect one reason SP recommends losing at a half pound per week for the final 10 pounds is to make the transition from "losing" to "maintaining" a smaller adjustment to lifestyle, increasing the chance of successful maintenance. 

So I sit here paralyzed by analysis, and don't increase my target calorie range. I have made some small efforts to eat toward the middle of the range instead of the low end some days. I'm also mindful of the fact that next week I start evening commitments on Tuesdays and Wednesdays. The additional time spent on these cannot help cutting how much exercise I really get. I don't want to get used to eating 300 more calories per day, then have that level of consumption be too much for my exercise level in the fall. 

One thing SP has given me, for sure, is a way to adjust my eating by small amounts and know that I've made the adjustment. If it turns out that the weight starts going up when the summer exercise frenzy cools down, I can tell the fitness tracker that my calories burned goals are lower and it will lower the ranges for me. If I see that I'm losing weight uncomfortably fast for where I am, I can tell it I'm burning more calories and it will raise the ranges. I can make the mechanism work, and I can follow the ranges. 

Now if I can just figure out when I need to adjust the ranges, I'll be all set.