I sometimes do what I think is referred to as fartlek training which basically is run at close to normal speed for between two sets of lamp posts, then sprint between the next two, and so on, so a third of the distance is sprints. I’d only start doing this halfway into a run, but if you’re only going out for half an hour it varies things up a bit.
In terms of weight loss I was told many years back that short runs are little use, and the energy comes from the muscle store; you only go on to biting the fat one you get past of 5 or 6 miles, so far loss comes from doing an 8-10 miler once a week in with your shorter runs. In the past when I did one 3 mile, one 6 mile and one 10 mile run each week the weight really did come off. Now I’m just doing 3 x 3 miles runs a week very little weight is coming off!
edit - hill sprints sounds great too - I like running up hill more than down.
Apparently Seb Coe when he trained in Sheffield never ran down hill - he’d run out of Sheff up the hills then he’d hop in his Dads car and go home. Let us know how you get on with them.