Fitness

Based on your comment about weight loss, I'll assume you're aiming for a "fat burning heart rate". While it's true that your body burns more fat at that heart rate, it also burns less total calories. Your body will generally always burn fat, but sometimes when we work harder it also has to dip into faster energy like carbs/glycogen.

All this means is that if you prefer a harder, shorter workout, there's no harm in it. There's a limit to this of course, but as long as you're getting a reasonable duration of exercise it should be fine.

Check with your doctor, if your heart is jumping that fast you might need a beta blocker. I am on one and it's a lot of work to get my bpm out of resting. If I forget it one day I can tell next time I am working out because my heart goes from 100-140 in a few seconds on my elliptical.

Also doing cardio will strengthen your heart and make it take more work to raise so if you want it to stay lower you will need to work it harder.

Probably a bit late to answer, but thought I'd leave a comment anyways. For reference I've lost quite a bit of weight in the past and am now an avid runner.

In my experience weight is like 90% lost in the kitchen through diet and not through sport. Compare how much calories/h moderate intensity sport burns, which as a side effect makes you a bit more hungry, vs how much even a small snack or glass of suggary soda has and you'll see that reducing intake is much easier.

The benefits from sport are imo primarily better health and wellbeing from the fitness gains you make.

Gains will take time, however i don't agree that you aren't making process. Don't you write yourself that you started with 30min have now doubled that? That's the definition of progess.

I don't know about (incline walking) and if there is a recent hype about that sort of stuff, but in running MAF/Maffetone training is a very similar method aimed at low/medium effort with constant heart rate. Hype around it kind of comes and goes, and it's nothing new.

It of course does improve fitness especially in anyone who starts from nothing, but to my knowledge the consensus is firmly that it is not the optimal or most effective way to train. Also substantiated by no professional training this way.

The usually recommended approach is some form of polarized training, where you do high and low intensity sessions that target different physiological adaptations. One rule of thumb in that regard is 80/20, which describes a rough split in training volume with 80% at low intensity and 20% at high effort.

So my recommendation in regard to weight loss would be to keep at it with whatever already seems to be working, particularly in regards to your diet. And if you want to see more progress on the fitness side, then start to incorporate some short higher intensity workouts of any kind into your training. There's nothing unhealthy about higher heartrates during training.