I think you will be burning more carbs than fat in these sessions. More easy/moderate but longer periods of exercise burn around 50:50 carbs:fat. The higher the intensity, the more that ratio skews towards carbs, which will make you hungry to replace those carbs. It's probably the walks that made a difference. Just speaking from my own experience, as I've lost about 12kg (nearly two stone) since I started running at the end of June, without making any changes to diet (in fact, I eat more). Most of that weight loss occurred when I did all my runs slow. Since I've started training and doing hard sessions, I've just ended up eating more, which has kept my weight steady. If I wanted to lose more weight, I'd add more slow miles rather than hard sessions.
Science and studies dispute on this matter, actually the opposite of your claims from more studies that I've read, and also from a personal experience I've never felt more hungry when added HIIT to my training, on the contrary really. And studies do show that it brings up your metabolism rate for much longer
"almost 10% more calories during the 24 hours" (
http://www.simplyshredded.com/fit-with-hiit-science-is-dropping-the-hammer-on-endless-bouts-of-steady-state-cardio.html).
- Several linked studies in this post.
As well as being more effective in burning fat, rather than muscles (
https://www.acsm.org/docs/brochures/high-intensity-interval-training.pdf• insulin sensitivity (which helps the exercising muscles more readily use glucose for fuel to make energy)
• cholesterol profiles
• abdominal fat and body weight while maintaining muscle mass.)
http://www.bodybuilding.com/fun/ask-the-ripped-dude-hiit.html"Another study by M. Sanchez Pacheco found that rats which performed high-intensity exercises lost more fat than the rats which performed low-intensity exercise. The rats which exercised at 80-90% of their maximum heart rate lost a significant amount of body fat compared to the rats which exercised at 60-70% of their maximum heart rate.
Many research studies found that long endurance activities like marathon running can cause muscle catabolism, or the breakdown of muscle tissue. Muscle catabolism can sometimes last up to 7 days after the endurance activity takes place.HIIT training on the other hand, can help increase speed, power, endurance and metabolic rate, helping you burn fat faster. Professional athletes incorporate HIIT into their workout routines because it has been proven to improve athletic performance."
I'm far from being having scientific study experience, at least not anything more than personal experience, which I clearly know from myself that it has helped me too: A) Burn more fat and B) Never increased my hunger/appetite, rather the contrary.
"HIIT vs Continuous Endurance Training: Battle of the Aerobic Titans""HIIT vs. Continuous Endurance Exercise: Cardiovascular Adaptations
Recent work shows that the cardiovascular adaptations to HIIT are similar to and in some cases superior to those of continuous endurance training (Helgerud et al., 2007; Wisløff, Ellingsen, & Kemi, 2009). Helgerud et al. showed that 4 repetitions of 4-minute runs at 90-95% of heart rate max (HRmax) followed by 3 minutes of active recovery at 70% HRmax performed 3 days per week for 8 weeks resulted in a 10% greater improvement in stroke volume when compared to a long, slow distance training group. Additional research by Slordahl et al. (2004) demonstrated that high intensity aerobic training at 90-95% of maximal oxygen consumption (VO2max) increased left ventricle heart mass by 12% and cardiac contractility by 13%, which is comparable to cardiovascular changes observed in continuous aerobic exercise."
https://www.unm.edu/~lkravitz/Article%20folder/HIITvsCardio.html