Honestly, I don't know my body fat percentage. I weight 178 and I'm 5' 9". Back in high school (several years ago) I was into weight lifting and put on some muscle mass, but never bothered to get rid of the fat covering it.
You are over 18 yrs. old with probably around 20% bodyfat I would guess.
12% - 15% bodyfat is pretty good for both performance and looks. Losing 15 pounds will get you in this range.
If you want those all important "6-pack abs", you are going to have to get down to single digit bodyfat levels. You would probably need to lose 25 pounds (or more).
The first 15 pounds will probably be relatively "easy". You could probably lose 1.5 pounds / week and get the job done in about 3 months if you work hard.
If you want to lose the next 10 pounds, that will probably prove much tougher. You would be lucky to lose 1 lb. / week. These next 10 pounds would probably take you another 3 months or so to lose.
Now, precisely how you go about losing the weight is another matter altogether. You need to estimate your "maintenance calories" (and there are several websites that have calculators that can help you). A simple rule of thumb for starters is to simply multiply your weight by 13 (178 * 13 = 2,300). For effective fat loss, you basically consume between 70% and 100% of that amount. You don't want to go too low or your metabolism will slow down. Most people have more luck varying their caloric intake (having "high" and "low" days).
Almost everyone will have to deal with their body slowing down their metabolism in response to cutting calories. Most people use "re-feed days" to reset their metabolism. You can look up what this means, but basically you eat big for a day so your body doesn't think you are trying to starve it. It will speed up your metabolism in response and then you can continue with the calorie restriction. If you don't do the re-feed's you will be fighting a tough battle as your body will continue to slow down your metabolism as you continue to cut calories. You'll know it is time for a re-feed when you are working your ass off on both diet and cardio and not seeing any results (sometimes you may actually be gaining weight). You will be frustrated and wondering WTF is going on. Answer is that your metabolism has slowed down and you need to get it back up to speed.
Next, you need to exercise (like you are doing). It isn't like HIIT is some magic weight-loss bullet. It is just one tool you can use. Play tennis, ride a bike, go for a run, or whatever else you feel like doing. You will get a feel for how much cardio is too much / too little / just right. Your body adapts, so usually you have to keeping upping the amount and / or intensity every so many weeks (and this adaptation varies by person).
Also, it is a good idea to lift weights (like you are doing) so you don't lose muscle as you diet. You don't need to do anything special or lift extremely heavy. Just simply workout 3 days / week or so. Make sure you work the entire body.
Dieting / fat loss is more about "punching the clock" everyday. There isn't any "magic" plan or magic food or magic pill or whatever. Just keep at it consistently and monitor the feedback you get from your body.
Generally for guys you will know if your weight loss (meaning your bathroom scale has a lower number today than it did last week) is fat loss by also using a tape measure in 3 areas: 1) Your waist just over your bellybutton; 2) Your illiac / belt line. This is just over your pelvis bone and just below your "love handles"; 3) Your hips at the widest protrusion of your buttocks.
If you are not seeing these 3 measurement decreasing, odds are that you are just losing water and other stuff, but not fat.
Good luck!!!
