Many of them, mostly focusing on full body, with short rest breaks. Just as an example, my right hip is ful of osteoarthritus , a degenerative condition, so any type of hi impact, such as running is out. So, for a metabolic boost, I use complexes, which are circuits done without rest, same weight, easiest to hardest (done with no rest, it makes the hardest pretty darn hard with a somehat light weight). Clean or snatch grip hi pull to neck X6, clean or snatch grip power snatch X 6, either front or back squat -push press combo X6, good morning X10, Chin Xbwt X 6-10, Pbardips X bw X10. I just did this yesterday w/40. 55, 65, 75,75 lbs and finished in 14 mins. I was breathing like a Rhino for a while afterwards. I took 30-60 secs between rounds. It's comparable to HIIT cardio. I did this in the morning just to get the joints loosened up and the blood flowing. Later, I did a "normal" strength based workout. For more ideas, just think the most work, with the most amount of muscle involved, in the shortest period of time. That will get you into fat loss, but don't forget your diet, it's critical. For more fat loss ideas, see crossfit.com What never fails to spin me up, is why people looking for fat loss, think they have to train like a bodybuilder, i.e. isolating musle groups, long rest periods. For fat loss, get the whole body involved. After you've lost the fat, you will find you've toned up quite nicely, and if you have bodybuilding goals, then go for it, and train by bodyparts, but set the groundwork first. You will also find that your work capacity has improved immensly.
Even Franco Columbo, one of the greatest bodybuilders that ever was, recommended beginners to start out with basics, as in compound movements, with short rest breaks, and in the 10-20 rep range. Apparently he thought this was necessary to build a "bae" and lean out.Most sports conditioning programs do similar, i.e. circuits of full body moves, short rest breaks. This is to cut bodyfat, and build a work base.
OK, now you are going to ask, why short rest breaks? Right. Do some research, but there have been many studies done by many exercise physiologists done with different protocols. Stone, Berger, Kraemer and Fleck, and the list goes on. What they found, was multiple sets, done with compound and multicompound exercises (think squats, deads, snatches, clean push press, row, chins, dips or BP) in the 70% 1 RM, done with a work time to rest ratio of 1.5:1
or even shorter rest breaks, resulted in a much greater output of natural gh hormone output than the other protocols. Think of it this way, keep a set working for 45-70 seconds, for most people thats in the 10-15 rep range with a 70% 1 rm. rest 30-45 secs, and go again. This way, you are not only burning some calories while working, but the gh hormone release is caus the body to burn fat, and repair, build some muscle.