Exercise as it relates to Disease/Short-term high-intensity interval training on body composition in overweight and obese young women

This is a critique of the journal article titled "Short-term high-intensity interval training on body composition and blood glucose in overweight and obese young women" by Kong Z, Sun S, Liu M, Shi Q, published in September 2016 in the Journal of diabetes research.

What is the background of this research?
Obesity is one of the worlds leading health issues, with over 1.9 billion people overweight in 2016 and of those people, 650 million people classed as obese. Epidemiological data shows that regular physical activity helps prevent obesity, cardiovascular disease, diabetes and hypertension. “Lack of time” being the main barrier for adults performing exercise, a more time efficient mode of exercise training has been developed. Both high-intensity interval training (HIIT; involves “near maximal” effort at intensities between 80-100% maximal heart rate) and low-volume sprint interval training (SIT; involves “all-out” or “supramaximal effort at the intensity of 100% of maximal oxygen uptake) are time efficient training strategies that can have positive impacts on health. There is a growing body of evidence to suggest that HIIT/SIT could reduce body mass, total or regional fat mass,   and waist circumference  and increase in fat-free mass. The purpose of this study was to compare effects of five weeks of HIIT intervention or moderate-intensity continuous training (MICT) on body composition and blood glucose as well as the systemic hormones that might influence body composition and blood glucose in overweight and obese young women.

Where is the research from?
This intervention was published in the Journal of Diabetes Research and written by Zhaowei Kong in 2016. Kong is an Associate Professor from the University of Macau and has been working there since 1991. He has been a part of over 50 research articles both English and Chinese with many of these articles focusing on obesity in a number of ways. His main research interests are physiological response and adaptation to exercise, hypoxic exercise and training and health and fitness.

What kind of research was this?
This research was a prospective cohort study taken over 5 weeks. The advantages of having a prospective cohort study is that it clearly indicates the temporal sequence between exposure and outcome. The study only had 22 eligible participants so following up on results wasn’t difficult. In comparison to retrospective cohort studies, the prospective cohort study will have fewer bias results as no information could be lost due to the study being taken out over a number of weeks instead of being looked back onto.

What did the research involve
This study involved female volunteers aged between 18 and 30 who had a classification of inactivity (doing less than 90 minutes of exercise a week for the past 6 months), and being overweight or obese, having a BMI over 23 and a body fat percentage over 30%. After completing a medical history questionnaire and a full physical examination to gain clearance to undertake vigorous exercise from a doctor, there were 22 eligible participants recruited to participate in the study. 11 participants were put in each group, the HIIT group and the MICT group, three participants from the MICT group and one participant from the HIIT group quit before completing the training intervention due to personal reasons. For five weeks each subject completed either the HIIT or the MICT exercise intervention, with four sessions per week.

Study Limitations
- The study had a small sample size with only 18 people participating, which limits the ability to draw meaningful conclusions regarding the improvement of body composition in response to HIIT and MICT.

- The study did not have a group of participants who did not participate in any physical activity for the two groups to be compared against.

- The timing of the intervention was done at the end of the year from mid-October to early December when people are more likely to gain weight. With evidence showing an average of 0.5 kg weight gain reported in fall and winter.

Study Strengths
- Pretraining measures were conducted during the follicular stage of the menstrual cycle for each subject, helps keep a reliable result to compare subjects.

- Appropriate tests were conducted and to a good standard.

- Recording of diet and other daily physical activity, taking into account external influences.

- Uses relevant and recent articles for research.

What were the basic results?
The study found a few key results:

- No significant differences on HR between the two groups (HIIT 164 +/-8 bpm, MICT 160+/-12 bpm)

- Both HIIT and MICT had a significant improvement in VO2peak and Peak power output (PPO) HIIT increased VO2peak by 7.9% and PPO by 13.8%, MICT increased VO2peak by 11.7% and PPO by 21.9%.

- No significant changes in weight, BMI, total fat mass and total body fatness for both groups.

What conclusions can we take from this research?
This study came to the conclusion that there was no significant changes or improvement in body composition after completing HIIT and MICT but there were improvements in their VO2peak and aerobic capacity. A further study showed that for a longer duration, 12–15 weeks there was an even higher improvement in their results for VO2peak and aerobic capacity. They found that HIIT was perceived to be easier than MICT when looking at the average bpm of each. For people who have limited time and want to get some exercise the HIIT sessions were just as beneficial as the MICT group but for a shorter duration. Another study done shows that there was only an improvement in the body composition of obese women using the HIIT course when also having a strict diet such as the Mediterranean diet.

Practical Advice
If you are a young woman struggling to lose weight and find the time to exercise the HIIT sessions would be beneficial for you. You should also consider changing up your diet as it accounts for roughly 80% of weight loss verses just 20% due to exercise. Any exercise is better than none though, so even taking an hour out of your day to go on a walk around your neighbourhood or nature walk is beneficial, with other research showing that even 2.5 hours of moderate activity per week can lower the risk of heart disease by 14%.

Further information
If you would like to find out more information have a look at these sites:

- Australian Physical Activity Guidelines https://www1.health.gov.au/internet/main/publishing.nsf/Content/fs-18-64years

- Overweight and Obesity in Australia https://www.aihw.gov.au/reports-data/behaviours-risk-factors/overweight-obesity/overview