Fitbit, Google Health, and What's Next
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.
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.
