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Hey, there! As you may be aware, TrendWeight is a web application that I originally created for myself, but then decided to make available for anyone to use. In reality, though, I am just a computer geek who likes to develop web applications in his free time—I'm not some big corporation with a team of support staff. That said, I am always willing to try to help or answer questions if you have them. Just email me at and I'll try to get back to you as soon as I can.

From time to time, I post on my blog when there are new features or important announcements regarding TrendWeight. You'll find the most recent blog posts related to TrendWeight below.

Odds are, you probably aren't interested in subscribing to my entire blog since it has posts about computer geek-y things not related to TrendWeight. So, if you want to stay in the loop with just TrendWeight things, your best bet is to follow @TrendWeight on Twitter or 'Like' the TrendWeight Facebook Page.

What's New with TrendWeight?

It's been a while since I posted any update on TrendWeight and so I want to take a moment at the start of a new year to share the latest...

New Features?

So what new stuff is coming for TrendWeight? The short answer is: not much. More or less, TrendWeight has all of the features that I want it to have (i.e. it's pretty close to "done".) I know many of you have made some great suggestions for ways that it could be enhanced in new directions by collecting new types of information (e.g. calories consumed each day, etc) and correlating that new information with the observed changes in weight, but after some consideration, I have decided to keep TrendWeight simple and focused on just what it does today.

There are still a small handful of minor improvements that I really want to make, but I don't plan to take TrendWeight in any significant new direction. For example, some people are using TrendWeight to track weight gain (they are building muscle, intentionally), but the arrow showing their weight change is red instead of green. Also, right now, TrendWeight has effectively a hard limit on the amount of historical data that it can store due to limitations on the amount of data that the FitBit API allows me to grab at one time. I'd like to address both of those issues sooner than later.

Technical Infrastructure

On the technical side of things, for a long time, I've been sharing with people that I was working on a significant rewrite of TrendWeight. That work has been stalled for a long time and I don't know when, if ever, that it will get moving again. Frankly, there was really no particular reason for the rewrite other than the fact that I thought it would have been fun to use rewriting TrendWeight as an excuse to play with some new technologies. There's nothing really wrong with the current TrendWeight codebase, and as my hobbies have evolved over time, I find myself spending less free time wanting to write code, so I may never get around to a general rewrite.

Never fear...

This post may come off a little bit negative, but I do not want people to get the impression that TrendWeight is going away. I have no intention to stop supporting TrendWeight, to stop fixing any bugs that crop up, or to take the servers down, so you can rest assured that the functionality you are using today isn't going anywhere.

As always, if you have questions or concerns, feel free to email me at

Dealing with Heartbleed

If you have been on the internet for the last couple weeks, you have likely heard of the Heartbleed bug. If not, read about it here. Here's what you need to know about TrendWeight.

FitBit and Withings Connections

FitBit has announced that they were affected (like many other sites) by this bug and they are recommending that FitBit users reauthorize third party applications like TrendWeight. I have not heard anything from Withings, but it doesn't hurt to reauthorize your Withings account just in case as well. Doing this is easy regardless of if you use FitBit or Withings.

  1. Go to your Settings page and scroll to the bottom.
  2. Click the Disconnect Scale button. This will deauthorize TrendWeight from getting at your FitBit or Withings data.
  3. You'll be taken back to a page where you can reconnect to FitBit or Withings. Once you do this, new authentication keys will be generated for you, and your data will be completely redownloaded (you won't lose anything).
  4. You're done. There is no step 4.

TrendWeight Itself

Our SSL provider, CloudFlare, has already fixed their servers, and in fact fixed them before the bug was made public. I have no reason to believe that anyone exploited the bug to attack TrendWeight prior to CloudFlare fixing the bug. That said, better safe than sorry, as they say. If you want to be extra cautious, you may want to consider changing your TrendWeight password here.

Isn't the Internet fun? If you have any questions, feel free to email me at

Fat Mass is Missing for Withings Users [Resolved]

Multiple Withings users have let me know that their Fat Mass data has disappeared from TrendWeight. Apparently something is going on with the Withings API. I don't know what the problem is yet, but I am investigating. Please stay tuned.

3/27 Update: I have confirmed with multiple users that the body fat data is simply missing from the data that the Withings API is giving TrendWeight. At this point, I don't know of anything I can do to change that. I still don't know why it is only happening to some people and not others. I have sent an email to Withings support asking if they know of anything that might have changed, and someone from Withings has already responded and is actively investigating the problem.

3/28 Updated: A developer at Withings emailed me to let me know that they found and fixed the problem. I confirmed that body mass data is once again appearing for several of the people who I know were affected and everything looks good. I automatically did a full resync for all Withings users who updated in the last week (which should catch anyone who might have been affected), so your missing data should now be back. If you notice anything wrong, though, don't hesitate to contact me.

And thanks to the folks at Withings for finding and fixing the problem so quickly.

Mystery Solved: FitBit Rounding Error

A long-standing mystery has finally been solved...

Short Version:

If your TrendWeight account is connected to Fitbit, and you don't use the metric system (kilograms), you may have noticed that the actual weights shown on TrendWeight were often different from the weights show on by 0.1 - 0.2 pounds. This doesn't happen anymore.

Long Version:

Sometimes Trendweight shows my actual scale weight as 0.1 lb higher or lower than what I remember the scale actually showing. I've noticed it on and off for a while, and I have gotten quite a few emails about it. I had looked into it in the past several times and confirmed that I am displaying exactly what Fitbit tells me in their API. So, I chalked it up to an idiosyncrasy on the Fitbit side. Who cares about 0.1 lb anyway?

Well, after yet another email today, I started looking into it again. After some research (aka Google searches), I found a couple other cases where people were having similar problems and in those reports was the nudge I needed to finally understand the problem. The problem is a rounding error when converting between Metric and English weight units. Here's what happens:

  1. You step on the scale and it displays your weight in pounds and sends it to the database.
  2. TrendWeight makes an API request and returns your recent weight readings in kilograms and rounded to 1 decimal place.
  3. TrendWeight converts your recent weight readings back into pounds.

The problem is the highlighted part of step #2. When your weight gets converted to kilograms and rounded to 1 decimal place and then converted back into pounds, the 0.1 - 0.2 lbs error gets introduced.

If only there was a way to tell the Fitbit API that I want the results in pounds (for users who are using pounds) so that I don't have to convert them myself, then this problem would go away... Oh wait. There is. Doh!

By asking Fitbit for weights directly in pounds, TrendWeight now gets actual scale weights that exactly match what was displayed on your scale and what you see on I should have realized this a long time ago, and so I feel a little foolish. Sorry.

TrendWeight's logic has been updated, and the next time you visit your dashboard, your weight readings for the past 21 days will automatically be re-downloaded and "fixed". That will result in an accurate current 'trend weight' (because that trend weight is based, essentially, on the past 20 days of weight readings).

If you really want to retroactively fix all your historical scale readings, you can do so by going into your settings and clicking the 'Resync All Data' button at the bottom of the page. However, do not click this if you have more than 3or 4 years of historical data in TrendWeight or you will risk running into the other Fitbit limitation that prevents TrendWeight from loading lots of historical data. If you have that much old data, you'll want to wait until that other limitation has been addressed.

Side Note

I also want to mention that I am actively working on a new version of the TrendWeight backend that addresses that Fitbit API limitation and also opens up the doors for addressing some of the long requested enhancements you all have made. I still have a bunch of work left to finish before it is ready, but at least the work is in progress...

As always, email me at if you have any questions or concerns.

iOS 7 and TrendWeight

I have gotten several reports of problems with using TrendWeight on iOS7 devices. Most commonly, I hear that TrendWeight seems to force you to login every time you open the site.

The underlying issue seems to be a bug or a series of bugs in Safari/iOS7 related to storing cookies. This Apple bug appears to affect all web apps, and not just TrendWeight, and other people are also reporting problems with iOS7 on this front. There have always been oddities in iOS with web apps that are pinned to the home screen, but it appears that iOS 7 made things noticeably worse.

Unfortunately, there is not anything I can do to fix the underlying problem, but I did make a small change that should cause TrendWeight to launch in the full Safari app instead of by itself. For some users, this seems to make your login session last longer, but it isn't a real fix and you'll eventually be asked to login again.

Until Apple addresses the underlying problems, there are two other workarounds I can suggest:

  • Instead of bookmarking your normal TrendWeight dashboard, bookmark (or add to your home screen) your public "sharing URL" (which you can find on your settings page). Your public "sharing URL" doesn't require you to login, so you won't see a login page when you visit that page regardless of if cookies are working or not.
  • You can also choose to use Chrome instead of Safari as a browser on iOS as cookies work fine in Chrome and so it will have no problem remembering your login.

If I hear more about the underlying Apple bug, I'll let you all know. Until then, if you have questions or concerns, email me at