Ultimately, weight loss is down to calories consumed vs. calories burnt. The different training modalities allow you to lose weight by burning either fat or carbs (hopefully, not muscle).
Now, people usually think that a good workout is the one that has you falling dead on the floor after long periods of non-stop sweating and panting. While that may be arguably effective and fun (and I’m being really benevolent here), we forget that it is actually in the lower intensity range where we burn more fat.
Zone 2 is when your heart rate is at 60-70% of its maximum, which translates into a light-moderate perceived exertion. And it is within this zone that your body uses fat for fuel, as opposed to carbs/sugars.
Training in Zone 2 could be anything, literally, from LISS (low intensity steady state cardio, such as jogging, fast walking, cycling, swimming) to body conditioning or also training for hypertrophy. The body doesn’t care whether you are jogging or performing squats in terms of fuel, as long as your intensity is within the range of Zone 2, and you keep it steady, it will use more fat than carbs.
So while high intensity interval training (HIIT) offers the EPOC effect (your metabolism will increase, meaning you’ll continue to burn calories after exercise), it is LISS (low intensity steady state) that burns more calories during exercise, and from fat (aside from other multiple health benefits, such as improving insulin sensitivity or capillary formation). Because it is a sustainable intensity, in order to yield benefits I recommend training for a minimum of 20min, up to a max. of 90min (stretching it a lot) per session.
Now, as a personal observation, bear in mind that training in this zone won’t necessarily yield long-term muscular benefits, or make you stronger. Although, depending on the programming, one can actually be surprised. The combination of low loads and high reps is one not to be taken for granted.