Fasted cardio is exersicing in a fasted state for the body to mobilize fat storage as fuel as oppose to metabolizing glycogen from digested foods in your body. It's usually done during a low baseline insulin period where food isn't being digested. (usually done first thing in the morning).
1) Is fasted cardio good for fat loss?
Yes and No.
2) Is fasted cardio good for you?
A- Depends on your goal.
B- Depends on your daily nutrition regime. You can't outrun a bad diet.
C- Depends on your current body fat percentage.
1) For one, when your body is engaged in High-intensity exercises such as HIIT, the body is going to mobilize carbohydrates for fuel. Fat is primarily mobilized during lower intensity cardio. Your body cannot process fat fast enough to power a High-Intensity workout, so it mainly goes to readily available Carb (glycogen stores) and just a little bit of fat. Walking fast or uphill walking in a fasted state will help you lose more fat than a HIIT class in a fasted state. (Google rate of energy production if you want more information on this. Make sure they are credible sources).
2) The primary benefit of HIIT cardio is the fact it helps you be in a calorie burning state AFTER aka POST the workout being complete (24-48 hours) not during the workout. So not eating before a HIIT workout to "lose" or "burn" more fat during the workout is not accurate. It will probably result in decreased blood sugar levels and light-headedness.
3) Fasted cardio needs to be planned around nutritional goals especially if the aim is to cut the fat storage and maintain muscle mass. The risk of muscle loss is increased during fasted cardio if proper nutritional standards for your program aren't set in place. (This includes protein intake pre or post workout). If your goal is muscle mass building, forget fasted cardio. If you are doing fasted cardio (Not HIIT), it is critical to eat or at least consume a protein shake right after the workout. This is because fasted cardio triggers the body to absorb nutrients immediately post workout. Make sure you refuel at the very least 20 minutes post workout.
4)If you are a male over 8% body fat or a female over 13-14% body fat, stick to improving and mastering your nutrition plan for your body instead of fasted cardio. Fasted cardio will help trim down stubborn areas after you have trimmed down as much as you think you could with a GOOD (again) GOOD DIET! For example, your nutrition is immaculate, but you still have the belly or hip fat you want to remove (Which comes in the small percentage ranges), Fasted cardio will help. But first, you have to have a great diet. You can get to 8%- 13-14% with diet and a healthy fitness routine.
5) Not to get scientific, but a caloric deficit from total daily energy expenditure (TDEE) (which includes physical activity levels) is the key to fat loss. If you do fasted cardio and cut 300 calories but then replace those 300 calories and end up at your baseline TDEE or even higher, guess what? You didn't achieve anything towards your fat loss goals.
6) How's your daily nutrition? What did you consume the night before? Do you suffer from low blood sugar? Hypoglycemia? Hyperglycemia? Diabetic? Talk to a nutritionist before you decide to engage in fasted cardio. Use your appropriate resources to maximize results.
7) Can you be sustainable with fasted cardio? Are you trying to lose body fat for a wedding in the summer? Then improve your diet and exercise on a daily basis months ahead of time not last minute. Are you looking to be fit for life? Again, fasted cardio (when done correctly) can help you trim body fat, however, how long can you keep that body fat off without a healthy diet and exercise routine. Stop looking for quick results and start being disciplined with your nutrition and exercise. Fitness should be about sustainability, not magic formulas. Get your mind right first! Get fit for life.
8) The only person who can efficiently provide you with a customized and tailored meal plan based on your goals, restrictions and body type is a nutritionist or a registered dietician. Do not hesitate to reach out to the NJ HIIT nutritionist and soon to be Registered Dietician Jessamyn Nucum - If you would like to know what to eat before a HIIT workout, please reach out to her at firstname.lastname@example.org. However, you have to be willing to make some positive changes in your daily nutrition. If you are not mentally prepared to make changes, improve your diet and nutrition, I suggest you get your mind right first. You have to be willing to help yourself improve.
Remember Nutrition comes first, you can't outrun a bad diet.