HIIT VS LISS debate and which should you be doing for fat loss? Well before we can decide we need to take a look at the differences amongst the two styles HIIT training also known as High intensity interval training is defined as short bursts of high intensity exercise combined with periods of lower intensity, between intervals. An example would be a 10-30 second sprint at maximal effort, then a light pace jog for 2 minutes, which would then be repeated for the desired number of intervals. Well before we can decide we need to take a look at the differences amongst the two styles HIIT training also known as High intensity interval training is defined as short bursts of high intensity exercise combined with periods of lower intensity, between intervals. An example would be a 10-30 second sprint at maximal effort, then a light pace jog for 2 minutes, which would then be repeated for the desired number of intervals. Low intensity steady state training or it’s abbreviation (LISS) is where you perform aerobic at a Low to moderate intensity exercise that remains at a steady state throughout without the use of maximal bursts or changes in intensity. A good example of LISS would be maintaining a steady paced walk for a desired time period (Commonly somewhere between 30-60 minutes). So know we know the difference what does the research suggest? Well it was thought for many years that LISS training was the most effective method for fat loss, due to its ability to burn fat for fuel during exercise. In contrast, HIIT training has been shown to use more carbohydrate stores for fuel. Research now suggests that what substrate you are burning within your session actually matters less and what is more important is what happens to fat balance over a 24 hour period . This has seen an increasing trend over recent years in favour of HIIT training. It is often said, that HIIT training burns more calories faster. However, according to the research this may not be strictly true. The premise is based on what is known as the ‘Post exercise oxygen consumption’ (EPOC). The belief is that if you train at higher intensities within your session you will burn more fat in the hours after your training, due to increased oxygen consumption, which is an adaptation that does not occur from LISS methods of cardio. Nevertheless a number of studies have shown that the effects of ‘EPOC’ is unlikely to account for any greater fat loss . Studies by Laforgia et al, (2006)  and Wewege et al (2017)  reported similar findings. Laforgia reported that effects of EPOC after an 80 minute HIIT workout lasted for 7 hours, but those 7 hours only equated to 80 extra calories burned. Whereas Wewege found no significant difference in calories burned between HIIT vs moderate continuous training (otherwise known as LISS training). So given the research there seems to be little to separate the two modalities. I suggest that providing you are recovering sufficiently, to choose which ever method fits around your routine and lifestyle best and gives you the most enjoyment. After all consistency is key. Remember that whichever approach you choose, whether it be HIIT or LISS, cardio should not be the main driver for fat loss. It can be used to assist however diet and a calorie deficit should be the key variables. .
References: 1. CONTRERAS, B., HELMS, E., FITSCHEN, P., SCHOENFELD, B. AND VENUTO, T., 2013. Cardio Roundtable with Bret Contreras, Eric Helms, Peter Fitschen Brad Schoenfeld Tom Venuto: Intensity and progression for fat loss and muscle retention. Alan Aragon Research Review. 2. KEATING, S., JOHNSON, N., MIELKE, G. AND COOMBES, J, 2017. A systematic review and meta-analysis of interval training versus moderate-intensity continuous training on body adiposity. Obesity Reviews, 18(8), pp.943-964. [Available at]: https://www.ncbi.nlm.nih.gov/pubmed/28513103[Accessed 10 Dec. 2018]. 3. LAFORGIA, J., WITHERS, R. AND GORE, C., 2006. Effects of exercise intensity and duration on the excess post-exercise oxygen consumption. Journal of Sports Sciences. 24(12), pp.1247-1264. [Available at]: https://www.ncbi.nlm.nih.gov/pubmed/17101527[Accessed 9 Dec. 2018]. 4. PAOLI, A., MARCOLIN, G., ZONIN, F., NERI, M., SIVIERI, A. AND PACELLI, Q, 2011. Exercising Fasting or Fed to Enhance Fat Loss? Influence of Food Intake on Respiratory Ratio and Excess Post exercise Oxygen Consumption after a Bout of Endurance Training. International Journal of Sport Nutrition and Exercise Metabolism, pp.48-54. [Available at]: https://www.ncbi.nlm.nih.gov/pubmed/21411835[Accessed 11 Dec. 2018]. 5. WEWEGE, M., VAN DEN BERG, R., WARD, R. AND KEECH, A, 2017. The effects of high-intensity interval training vs. moderate-intensity continuous training on body composition in overweight and obese adults: a systematic review and meta-analysis. Obesity Reviews, 18(6), pp.635-646. [Available at]: https://www.ncbi.nlm.nih.gov/pubmed/28401638[Accessed11 Dec. 2018].