Okay, thanks! Would you happen to have any suggested 3rd party apps?
i use an app called healthdash. it's OK and will do exaclty what you want, but i'm most appreciative of it because i deleted a year's worth of flights climbed data (oops) and was able to recover it manually - although with some effort - because it didn't flush it's cache, which was handy.
health is actually much more capable than many people are aware nowadays... i was surprised to learn a couple of things recently...
@Julien did you know you can find a summary of data from any day ever quickly by going to health data -> calendar (at the top) and then picking a date?
also, the health app itself is capable of giving you monthly totals, if you flip it to "year" and turn the phone in landscape it will show the monthly figures for each month and you can drag your finger along the bar to see each data point.
healthdash will summarise it for you better. it's probably worth the small cost involved.