If you use TrendWeight with a Fitbit account, there's a change coming that you should know about.
tldr: Google is retiring the API that TrendWeight uses to read weight data from Fitbit, and once it's gone, TrendWeight won't be able to sync from Fitbit anymore. And it's kind of gone already for new weights.
Update (August 24, 2026): The weight log and the API I mention below are no longer "coming soon" — they're done and live. See the "Your options now" section below.
What's happening
Google has folded Fitbit into Google Health. As part of that, they're shutting down the old Fitbit Web API — the one TrendWeight has always used to pull your weight from Fitbit. It goes away completely in September 2026, and once it does, the Fitbit connection stops working.
As far as I can tell, Fitbit has already stopped syncing new weight data to TrendWeight. You can still connect an account to get historical data, but new readings just aren't coming through anymore.
The new API, and the catch
Google offers a replacement for the old API called the Google Health API. Access is available to two groups:
If you want to use it for yourself or you have 100 users or fewer, you can get access as an individual and simply ask each user for their permission to download their data.
If you have more than 100 users, you have to pass Google's verification plus a third-party security audit, redone every year, because weight readings count as sensitive health data.
To be fair to Google, that's reasonable. Google Health holds a lot of personal information, and being picky about who gets access to it on behalf of their users is a good thing. But that second tier is built for companies — the kind that have compliance departments and are used to paying for security audits as a normal cost of doing business.
Why I'm not doing it
TrendWeight has well more than 100 people connected through Fitbit, so the personal/small-project tier isn't an option. That leaves the company tier: an annual third-party audit and all the process around it.
The full-scale approval process assumes you're a real company, but TrendWeight is a free project I run in my spare time. Taking on a recurring audit process — with the complexity and the nontrivial cost that comes with it — isn't something I'm interested in doing for a hobby project. So TrendWeight won't be supporting Google Health API, at least directly (see more below).
Your data isn't going anywhere
None of the Fitbit data you've already collected is affected. Everything that's already in TrendWeight stays in your charts exactly as it is. Nothing gets deleted, and TrendWeight itself isn't going anywhere. This only changes how new data comes in — not the history you've already built up.
One small caveat on that, though. Historically you've always been able to disconnect your Fitbit account and then later connect it to a new TrendWeight account later to redownload your historical data. That won't be possible soon. That means two things:
Make sure you use an email address with TrendWeight that you won't lose access to. This is the most common reason people end up needing to create a new TrendWeight account and re-attach old Fitbit accounts. You can change your email address or add multiple backup emails addresses on the Account Page.
Make sure you keep a safe copy of your Fitbit data somewhere other than TrendWeight (in case something goes wrong). You can download it from the Download Page.
Your options now
When I first wrote this post, the weight log and the API were still works in progress. They're both done now, so here's where things stand:
Withings still works, and it's not caught up in any of this. If you want automatic syncing from a scale, Withings is fully supported today.
The weight log is ready. If you don't want to buy a new scale, you can now just type your weight in directly, quickly and easily each day, on the Weight Log page. Turn it on from the scales settings page and your trend keeps going without any scale connection at all. It also works alongside connected scales, so you can mix and match.
The API is ready too. That 100-user limit actually works in an individual's favor — as an individual Google Health user, you can get your own Google Health API access without the audit or review process. So TrendWeight now has a documented API that you can use to wire up your own integration and push your data in (or pull it out — it can read your data too, including the calculated trend values). This one's for people comfortable with a bit of code. Grab an API key from the Settings page, and check out the API post for details and some example code.
Sorry about the disruption
Some of you have used the Fitbit connection for years, and I'm sorry it's going away. It's not a change I went looking for. I'd rather tell you what's coming now than have it quietly stop working one day with no explanation.
As always, if you have questions, reach out at erv@ewal.net.
About the author
I'm a father and husband, a software developer, a computer geek, a board game collector, and a heart transplant recipient living in Sun Prairie, Wisconsin.
Comments
Join the discussionThanks for keeping TrendWeight going, Erv.
My sync finally stopped worked several days ago. Many weight recording apps support recording metrics to the local Health Connect database on Android phones though, so I wrote a small app that syncs these values to TrendWeight using the API. In case anyone else is interested, I'm publishing this app on the Play Store. It's currently in the closed testing phase. If you want to try the app, you can access it by joining the hc4tw-testers google group ( go to groups.google.com and search for hc4tw-testers ) and then clicking on the link in the group to download the app from the Store (you need to join the group else the link wont work - Google's rules for closed tests).
I've bought a Withings Body Smart scale and it seems to work well. My Tanita scale was more than twenty years old so I felt it had done its time.
While I was setting up my Withings account (before the scale arrived) I noticed that I could get the Withings account to pull weight and other data automatically from Google Health, and then Trendweight was pulling the data from both the outgoing Fitbit API and also from the Withings account.
Could this be a solution for Fitbit users connected to Google Health? They create a Withings account and use Google Health Connect to automatically sync data from their Fitbit account to their Withings account. They then connect Trendweight to the Withings account and can see the data from their Fitbit account (via Withings, with no Withings device required).
Hopefully this will help some people if it works.
Al
I've been manually entering my weight/BF into Google Health to sync to Trendweight since Google killed the fitbit app a while back. I am not tech savvy enough to even think about attempting the API thing on my own. Any chance of getting an autosync set up with the Garmin Index S2 scale? If not, then I will just manually log my data directly into trendweight...but Garmin autosyncs with MyFitnessPal, so there must be a way to do it. :)
I have no plans to directly integrate with Garmin. They don't have an open API for hobby use. Manual entry in trendweight is likely the best option unless/until someone else figures out how to create a tool that bridges the two systems.
Erv, Thanks for all you do. I have used Trendweight for 13 years. I don’t use a Fitbit anymore, but I use an Aria scale. Will this change affect me? Thanks again, John.
Yes, the Aria Scale is a Fitbit product so it will stop syncing sometime in September when Google turns the old API off.
Hi Erv. I just tried the manual entry. It defaulted to my last weight (242.5), but when I edited the date and body fat and tried to enter it, it failed, saying I needed to add my weight. Believe it or not, I'm exactly the same today (242.5) as I was on June 24. Numbers are funny. Can you please review that? Thanks. bp
I'll fix the UI. It doesn't default to anything, rather it shows you as a subtle reminder in the text box what your previous weight was (as a reminder), but you still have to type that number in there. I'll move that reminder out of the text box itself so that it doesn't seem like it's already filled out.
Thanks, Erv. For clarity, I did try to type it in again, but it wouldn't accept my input. It seemed to lock out the field. I'll try again. Thanks.
Thank you, Erv. Your tools have been a huge part of my weight loss journey. I look forward to manual entry to show my long-term progress.
here forever. Will connect the personal API and see what else AI can help do.
As far as I can tell, Fitbit has already stopped syncing new weight data to TrendWeight
For what it's worth, my weight synced fine from Fitbit 10 mins ago
Yeah, it's intermittently working it seems.
