Maybe instead of only doing those "marathon" session, try to start using interval training sessions
as well and/ or some tabata's. the reason is the body adapts to the same thing and you have to "shock" your body.
(tabata is 20 secs of max work followed by 10 secs of rest, this is repeated 8 times, so 1 tabata round is 4 minutes of work).
few tabata examples are:
(the 16 minute workout)
- tabata squats
- tabata burpees
- tabata pushups
- tabata what you want (eg jump rope, more burpees etc etc etc).
this are only 4 rounds so 16 minutes). But I would not do tabata's every day, maybe add them 2 days a week to your routine instead of the hour tred work. (plus point is you save a lot of time also).
Also nutrition is important. First do NOT skip breakfast
(a good way can be a fruit breakfast as this digests quickly and gives you more energy as the body does not need energy for the digestion) and eat about 6 smaller meals a day (about 1 every 3 hours) and do not eat approx. 3 hours before going to bed.
Hope this helps.