[meroes]

Longer slower running burns more fat because your body isn’t forced to use as much glycogen as faster paced running.

I guess the answer for optimizing time is to get a home treadmill if removing the commute to a trail/track will make the timing work.

[nkmnz]

This is incorrect. Each minute of fast running bruns more fat than a minute of slower running. Longer slower running burns more fat only because you can do it for a longer period time, increasing total energy expenditure over the whole workout. If you want to maximize fat loss, you still need to maximize energy expenditure. If the available time is fixed and low, HIIT is the way to go. If the available time isn't fix or high relative to your capability to do HIIT, slowing the pace to fill the whole available time is the way to go.

[meroes]

Are you sure you’re talking about fat and not total calories? The whole premise about Zone 2 running vs Zones 3/4 is you really do burn more grams of fat at the lower Zone per minute.

https://cannonbol.com/blog/articles/Achten_%282004%29.pdf?ut...

[nkmnz]

You are right in the literal sense of "burning fat" = oxidation of triglycerides. I'm used to a more figuratively use of the term in weight loss discussions, referring to "losing body fat", which is the result of total calorie deficits, increased fat oxidation and reduced fat synthesis. Depleting the glycogen storage helps to reduce fat synthesis from ingested carbohydrates, so even if the fat molecules aren't burned directly due to the higher intensity, you'll lose more fat tissue with higher intensity.

But again, yes, in the literal physiological sense, you're right.