Does trend work by using the iPhone app or do i need the watch?

Hi lirio273,

That's a great question. If you don't see your trends, we recommend you try the steps via the link below in the section titled "If you don't see trends."

Track your trends in the Fitness app

It takes 180 days of activity to start your trends. If you don't see your trends, keep wearing your watch and closing your rings. When there's enough data, you'll get a notification that your trends are ready. 

We recommend the link above because it directly answers your question. If you don't see your trends, keep wearing your watch and closing your rings.

Please do not hesitate to contact us if you have questions or need any additional support.  

Thanks for using the Apple Support Communities.

Cheers!