HIIT is intense, fast and leaves us exhausted, which must mean that it makes us hungry, right? Surprisingly, it’s not quite so clear cut. In this article, health expert Leanne Edermaniger delves into the science of appetite and exactly how we should be fueling our HIIT.
The precise effect HIIT has on our appetite remains a topic of interest among exercise scientists. Some studies suggest that HIIT suppresses our appetite and therefore reduces our energy intake. However, there is also growing evidence to suggest that high-intensity exercise may improve the sensitivity of appetite hormones which in turn means that appetite is regulated much more effectively.
The science of appetite
Appetite is the desire to eat and can be influenced by both psychological factors and biochemicals. Interleukin-6 (IL-6) is a protein and signalling molecule secreted by various organs in the body and is associated with many processes within the body including appetite. IL-6 stimulates the release of hormones which are involved in the regulation of our appetite.
Research has shown that HIIT increases the activity of IL-6 and reduces the concentration of appetite-stimulating hormones such as ghrelin. Ghrelin is sometimes referred to as the hunger hormone because it stimulates our appetite and promotes the storage of fat. It’s mainly released by the stomach but can also be released in small amounts by the brain, pancreas and small intestine.
A study conducted by researchers at The University of Western Australia found that when a group of overweight men completed 30 minutes of HIIT, they were inclined to consume fewer calories afterwards compared to when they completed 30 minutes of moderate intensity exercise.
However, the research is conflicting, with some scientists suggesting that HIIT has no independent effect on appetite in some people, especially those who are overweight. What’s clear is that HIIT can induce similar physiological and metabolic effects as continuous moderate-intensity exercise which requires a far greater time commitment. In short, a 20 minute HIIT session could leave you just as hungry as an hour long run.
The jury’s still out on exactly what effect HIIT has on our appetite, but what we know for certain is that good nutrition is key to optimizing training performance. It goes without saying, but following a diet rich in carbohydrates, protein and healthy fats is a surefire way to set yourself on the path to HIITing your training goals.