High-intensity interval workouts might be a 'HIIT' but they don't fight flab

13 May 2014

High-intensity interval training (HIIT) is touted as the fastest way to get lean, but according to ground-breaking new research from the University of Sydney's Charles Perkins Centre, only endurance exercise goes the distance if you are chasing fat loss.

The world-first controlled trial led by exercise physiologists Shelley Keating and Dr Nathan Johnson from the Faculty of Health Sciences reveals regular continuous aerobic exercise yields better fat loss results than HIIT workouts for overweight people looking to shed weight and achieve a slimmer waistline.

"A growing number of people are substituting HIIT for regular aerobic workouts in their exercise routine, but high-intensity interval training is not a fast track to quick fat loss if you're overweight," said Ms Keating.

"High-intensity burst training does deliver important benefits like increased fitness, but it doesn't have a 'fat furnace' effect if you carry weight around the middle.

"The message is if you're hitting the gym to lose weight and trim your waistline, stick with steady aerobic exercise to shift abdominal fat and see better results on the scales."

The new research from the University of Sydney's Charles Perkins Centre is the first controlled study of its kind to compare the effects of HIIT and continuous aerobic exercise on body fat levels among overweight adults.

"Some trainers spruik high-intensity workouts as the most efficient training method, but this doesn't mean HIIT translates to fat loss if you're overweight," Dr Johnson said.

"Until now the only evidence to support claims for the effectiveness of high-intensity workouts as an efficient weight loss method was research examining ; younger people or people who were already lean and healthy.

"HIIT can be used as a time-efficient training method to improve fitness, but if you're overweight you can't afford to dump aerobic exercise if you want to see fat loss."

Lead researcher Shelley Keating said the study, published in the Journal of Obesity, had implications for the management of weight loss.

"Some trainers emphasize HIIT workouts over continuous exercise to target body fat and trim the waistline, but the evidence is if you're overweight you're better off focusing on continuous aerobic exercise to slim your core and positively improve your body fat composition," Ms Keating said.

"Forget the claims HIIT workouts can whip overweight people into shape in less time than regular aerobic exercise - it's more efficient to workout regularly at a continuous intensity to achieve a fat loss goal."

The Charles Perkins Centre study examined the effects of HIIT versus endurance exercise training three days a week on body fat levels in overweight adults seeking improved fat distribution. The HIIT workout consisted of bursts of high-intensity output (120 percent of VO2peak) interspersed with lower intensity activity while the continuous aerobic exercise was a consistent workout at a steady intensity (65 percent of ; VO2peak).

The Charles Perkins Centre is a world-leading initiative that brings together international leaders across a broad spectrum of academic disciplines to find real-world solutions to obesity, diabetes, cardiovascular disease and related conditions. ;

The state-of-the-art Charles Perkins Centre building, a $385 million teaching and research hub on the University of Sydney's Camperdown Campus, is set to officially launch in June.

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