z2 training and 'fat burning'

as i'm doing a ton of z2 training currently, in part to buff up my mitochondria but also to take care of my grumpy heart, so it was interesting to hear it being discussed in terms of 'fat burning'. me, dependent on the length of the session and what my heart rate's up to (resting heart rate pre sesh in the ageing gent - it's important!), i'll add in a couple of sprint sessions to take my heart up to its aerobic maximum and z5/6 power output plus some ugly weight sessions (tho with caution - see ageing gent above! lol). as ever, i advocate for yoga moves as well!

here's the lovely eugene teo doing a reasonably decent explanation of it