High-Intensity Intermittent Exercise and Fat Loss

Abstract

The effect of regular aerobic exercise on body fat is negligible; however, other forms of exercise may have a greater impact on body composition. For example, emerging research examining high-intensity intermittent exercise (HIIE) indicates that it may be more effective at reducing subcutaneous and abdominal body fat than other types of exercise. The mechanisms underlying the fat reduction induced by HIIE, however, are undetermined. Regular HIIE has been shown to significantly increase both aerobic and anaerobic fitness. HIIE also significantly lowers insulin resistance and results in a number of skeletal muscle adaptations that result in enhanced skeletal muscle fat oxidation and improved glucose tolerance. This review summarizes the results of HIIE studies on fat loss, fitness, insulin resistance, and skeletal muscle. Possible mechanisms underlying HIIE-induced fat loss and implications for the use of HIIE in the treatment and prevention of obesity are also discussed.

The impact of high-intensity intermittent exercise on resting metabolic rate in healthy males

“…Consequently, the impact of HIT on energy balance appears to be chiefly determined by alterations in metabolic rate that occur solely during exercise, and not after. These findings may suggest that modifications in post-exercise metabolic rate (EPOC) are unlikely to be responsible for previously documented changes in body weight/composition that have been reported in response to HIT (Boutcher 2010). Additional work is needed to confirm this however given that changes in body weight/composition have previously been reported in individuals who are overweight/obese.…”

“…An intriguing body of research has also emerged documenting beneficial changes in body composition and/or mass in response to HIT (Boutcher 2010) with studies reporting favourable changes within short time-frames. Accordingly, Whyte et al (2010) subjected overweight and obese males to six training sessions over two weeks with each session consisting of four to six 30s Wingate sprints, interspersed with 4.5 min of recovery.…”

“…Specifically, how high intensity intermittent exercise (HIIE -representing one single bout of HIT) impacts upon EE and substrate utilisation, both during and after exercise, is not well understood. Given recent reports demonstrating notable changes in body composition and/or mass with HIT (Boutcher 2010) it is necessary to understand how HIIE influences these parameters. Recent reports have provided preliminary information on this issue (Williams 2013;Chan & Burns 2013;Hazell et al 2012) however in these studies the focus has been on sprint interval training i.e.…”

Physiological and molecular responses to an acute bout of reduced-exertion high-intensity interval training (REHIT)

“…These findings are of importance as several previous studies have observed reductions in fat mass following HIT with some evidence for superior reductions compared with traditional aerobic training (Whyte et al 2010;Gillen et al 2013;Heydari et al 2012;Trapp et al 2008). Since direct exercise energy expenditure is much lower with HIT compared with aerobic exercise, the (potentially superior) reductions in fat mass following HIT have been hypothesised to be a result of either an increase in energy expenditure through a more prolonged EPOC and/or a reduction in energy intake through suppression of appetite (Boutcher 2011). There are now several studies reporting that HIT results in an increase in total daily energy expenditure (Hazell et al 2012;Skelly et al 2014;Beaulieu et al 2015;Sevits et al 2013), and this increase is similar to that elicited by 30-50 minutes of moderate-vigorous aerobic exercise (Hazell et al 2012;Skelly et al 2014).…”

“…It has also been suggested that HIT may result in suppression of appetite after exercise and hence lead to a reduction in energy intake across a training intervention (Boutcher 2011). The gut hormones acylated ghrelin (orexigenic effects) and PYY (anorexigenic effects) have emerged as important episodic regulators of hunger, feeding latency and caloric intake and may therefore play a role in mediating any changes in appetite with exercise (Stensel 2010;Wynne et al 2005).…”