Are short bursts of intense exercise better for weight loss?

“We have known for some time that high-intensity interval training (HIIT), which is exercise involving repeated bursts of intense effort interspersed with low intensity recovery, is effective for improving sports performance.  Research by Izumi Tabata and colleagues in Japan demonstrated improvements in fitness following HIIT more than 20-years ago.  Recently, research efforts have considered if this type of exercise could be used to improve health outcomes in non-athletic populations.  The reason for this interest is that perceived ‘lack of time’ is the most commonly cited barrier to exercise.  Best evidence recommendations encourage at least 150 minutes of moderate-intensity aerobic activity per week, but HIIT is typically considered to be more time-efficient than this.

Whilst we have strong evidence that HIIT can rapidly improve our fitness and insulin sensitivity, both of which are very important for health, less is known about how HIIT impacts levels of body fat.  A recent systematic review and meta-analysis published in the British Journal of Sports Medicine showed that interval based exercise results in more fat loss than traditional moderate-intensity exercise.  From the 36 studies included in the analysis, the average weight loss following HIIT was 1.6 kg (3.5 lb) compared to 1.1 kg (2.5 lb) following moderate-intensity exercise.  This finding has subsequently received media attention, where it is of course tempting to conclude that HIIT is the best option for weight loss.  Whilst HIIT may potentially be an important part of a weight loss intervention involving exercise, we should scrutinise this finding further.  The studies included in the review used different methods and different interval exercise protocols.  Some of these were not genuinely time-efficient, thus it is unlikely that people would be more likely to adhere to these exercise programmes in everyday life.  The high-intensity nature of HIIT may also be a barrier for many.  Another issue is that most studies included in the analysis were carried out under supervision in a controlled-laboratory setting using specialist exercise ergometers.  It is less clear how well HIIT can be implemented in real-world settings.  Furthermore, there is not enough evidence to suggest that HIIT could be adopted by everyone, particularly those with non-communicable diseases, and the approach could even be hazardous for high-risk and sedentary individuals.

In short, HIIT is one of several exercise options that we have available to us to regulate our body weight and improve our health.  The potential to induce beneficial adaptations in a more time-efficient manner should not be overlooked.  However, the acceptability and accessibility of the activity to those for whom the intervention is intended, and the practicalities of building the activity into everyday life, also need to be considered.  A key challenge remains to translate current evidence to practical approaches that are both tolerable and time-efficient in real-world settings.”