There are supplements you can take that will allow you to lose fat faster than without. Just looking at the ECA stack for a minute, from a peer reviewed study:
Conclusions: In this 6-month placebo-controlled trial, herbal
ephedra/caffeine (90/192 mg/day) promoted body weight and body fat
reduction and improved blood lipids without significant adverse
However, numerous deaths can be attributed to ephedra and ephedra like substances:
The use of dietary supplements that contain ephedra alkaloids may pose
a health risk to some persons. These findings indicate the need for a
better understanding of individual susceptibility to the adverse
effects of such dietary supplements.
No one is going to credibly argue that something like the widely consumed ECA stack is ineffective. Also, no one with much brain power is going to going around recommending it.
As you noted, it was the strict adherence to your diet that made the biggest difference and at a high (>20%, for males) body fat, diet is the largest valve to play with by far. I'm not going to recommend an ECA stack for anyone, but the generally successful results I've seen are from folks who use it on a short term basis to dip into the <10% range, because the lower your body fat goes the easier it is to add body fat.
My honest advice would be to use an effective strength training program that has you lifting every other day, and then go for runs or long (1 hour+) walks on the other days. That schedule, combined with a strict diet, will scrub fat quite consistently. And remember that strength training has a higher impact to fat loss than cardio.
"Fat burners" you can largely ignore for your entire fitness life and have great results. If you do venture down that road, I would strongly encourage you to:
- Skip HIIT
- Don't run in the heat
- Stay very hydrated
- Start with a much lower dose than whatever the bro-science on the Internet tells you
- Tell your doctor what you're doing.
Fat burners will increase your blood pressure, induce tachycardia, and raise your core temperature: deadly things if your body has existing cardiac issues or is trying to cool you down during normal exercise. People do die.