Yeah, exactly. My normal scale was missing the big picture of how my weight fluctuates month-to-month. I do need to implement some smoothing, though, as the raw daily value isn't as useful.
The withings web app has something built in to automatically pipe the data to LoseIt.com, there are several other options as well. I do that because I prefer the interface on LoseIt. You could probably also implement the api for one of those sites if you didn't want to handroll the whole thing.
Daily weigh-ins can be very consistent if you weigh yourself in the morning at about the same time after using the toilet, and before eating/drinking anything.
That's why I want a smoothing algorithm, but the one I found here[1] is giving me a bit of a problem (I can't see why the data points are being squeezed).
Relative to your overall weight, that doesn't seem like it's highly variable, but I've never been much for stats. Try weighing yourself daily after dinner and see the difference.
How much water do you drink per day? I have found that in times where I'm not drinking enough water, my weight will fluctuate more.
Nah, it's not that variable, it just fluctuates a bit. By "it's not as useful" I mean that weight loss/gain happens at larger timescales, so you can't look at normal daily noise and say "omg im so fat".
I think the noise has more to do about the time you last drank water (right before bed, for example), also the time you last ate (the later you eat, the more food you'll still be digesting when weighing yourself). It's not a problem by any stretch, it's just normal data variance.
Worth noting: the author of the Hacker's Diet, John Walker, explains why his choice (exponentially smoothed weighted moving average) is a good choice of smoothing function (vs. some other common functions) for tracking weight over time. See the section "Signal and Noise".
Seconded. I can often predict my weight to 200g if I have a similar diet for a few days running. That said, I have two pairs of scales. Both give reliable results, but one is consistently 500g off from the other. I wouldn't be surprised if most consumer scales have similar levels of inaccuracy. Not a problem for weighing yourself perhaps, but potentially an issue for plane luggage...
