Exercise as it relates to Disease/Effects of aerobic and/or resistance training on body mass and fat mass in overweight or obese adults

Article critiqued - Willis, L. H., Slentz, C. A., Bateman, L. A., Shields, A. T., Piner, L. W., Bales, C. W., Houmard, J. A. & Kraus, W. E. (2012). Effects of aerobic and/or resistance training on body mass and fat mass in overweight or obese adults. Journal of applied physiology.

This article critique is an assignment for the unit; Health, Disease and Exercise at University of Canberra, Semester 2, 2020.

What is the background to this research?
The 2009–2010 National Health and Nutrition Examination Survey found that 75% of U.S adults aged 20 years and older are overweight, obese or extremely obese. This may indicate that exercise guidelines are not being met or appropriate modes of exercise are not being utilised. Obesity is a condition that can cause mortality due to the increased risk of chronic disease and cancers. It is widely supported that exercise can decrease body mass and fat mass in overweight and obese individuals, however, there are limited recommendations of exercise modes which are most effective in achieving this. Exercise guidelines have often focused on endurance or aerobic training to treat weight loss and maintenance, recent studies have shown that resistance training can also be effective in reducing fat mass.

Where is the research from?
Willis, Slentz, Bateman, Shields, Piner, Bales, Houmard, and Kraus conducted their research and testing at Duke University Medical Center and East Carolina University in North Carolina. The protocols for the study were reviewed by the institutional review boards at each university. There were no conflicts of interest, financial, or otherwise declared by the authors. Funds were provided by the National Heart, Lung, and Blood Institute, the third-largest Institute of the National Institutes of Health. The authors in this study are well established and have a variety of experience and published articles related to obesity, chronic diseases, and physical activity.

What kind of research was this?
This study was a randomised comparative effectiveness research trial of overweight and obese adults with cardiometabolic risk factors.

What did the research involve?
119 sedentary, nondiabetic, overweight or obese adults were selected from 3,145 that responded to newspaper, magazine, internet, and word of mouth advertisements at Duke University and East Carolina University. Participants were randomised into one of three 8-month exercise protocols:
 * 1) Resistance training 3 days a week, 3 sets a session, and 8-12 repetitions per set
 * 2) Aerobic training calorically equivalent to 12 miles a week at 65-80% peak VO2
 * 3) Resistance and aerobic training combined requiring double the time commitment

Nutrition, body composition, weight, height, and waist circumference were measure pre and post-exercise intervention. Greater investigation of factors such as missed sessions, calorie intake, and energy expenditure would have provided further insight into the results of individuals. Body composition was measured using either a BOD POD or DEXA allowing lean mass and fat mass to be measured accurately. Calorie intake was calculated pre and post-exercise intervention using a 24-hour recall interview and 3-day food record. Using a 24-hour recall was a limitation of the study as it requires subjects to rely on memory, honesty, and may not reflect their usual intake. Computed tomography was used to measure the change in thigh muscle area which adds validity to methods used to measure body composition. A cardiopulmonary exercise test with a 12 lead ECG was used to measure absolute peak VO2 and heart rate monitors were used at each session.

What were the basic results?
Key findings of this study
 * Group 2 and 3 reduced total body mass and fat mass more than group 1
 * Group 1 and 3 increased lean body mass more than group 2

The study implies that there is conflicting research in regard to whether or not resistance training reduces fat mass. The study has effectively discussed how resistance training has been perceived in other studies and acknowledges they have failed to show resistance training results in a significant total body and fat mass loss. Multiple studies within the discussion emphasize resistance training alone does not show a decrease in fat mass however it is equally effective as aerobic training in decreasing the risk of cardiovascular diseases. Nutrition results in this study were not significant or evident in the discussion, further research was needed. Results could have been different if subjects did not volunteer, were not supervised, and relied on their own self-efficacy. further to this outside of the study, it may be difficult for the general population to access heart rate monitors and know 65-80% of their peak VO2.

What conclusions can we make from this research?
It can be concluded that aerobic training alone is the best mode of exercise to reduce body mass and fat mass in nondiabetic, overweight, and obese adults. Resistance training and aerobic training combined did not show a significant decrease in fat mass and body mass compared to aerobic training alone. Resistance training showed an increase in lean muscle mass but did not decrease fat mass or total body mass. whilst the study did not place a great emphasis on this, it is evident that resistance training and aerobic training combined showed a greater decrease in waist circumference compared to aerobic or resistance training alone. This is supported by two studies that demonstrated visceral adipose tissue decreased after a resistance training intervention.

Practical advice
This advice relates to those who are over the age of 18 with no present cardiovascular diseases or those who are nondiabetic.
 * If the goal is to gain lean mass than resistance training at a total of 180 minutes a week is the optimal mode of exercise.
 * If the goal is to maintain weight and reduce the risk of cardiovascular risk a combined program of resistance and aerobic exercise is the most appropriate mode of exercise. Aerobic training at 65-80% peak VO2 for 133 minutes a week and resistance training for 133 minutes a week is optimal.
 * If the goal is to reduce fat mass and total body mass aerobic training alone is deemed to be the most effective mode of exercise. This should be completed at 65-80% peak VO2 for over 133 minutes a week.

Further information/resources
This study supports the widely accepted notion that aerobic training can decrease total body mass and fat mass, although further research is needed to investigate the effectiveness of resistance training in combination with aerobic training on obese and overweight individuals. This study demonstrates that resistance training does not directly decrease fat mass, there are however other benefits it can have on obese or overweight adults with cardiometabolic risk factors which warrant further investigation. In addition, energy expenditure and calorie intake could be examined further to determine if aerobic and resistance training combined with a low-calorie diet can enhance weight loss. A decrease in calorie intake is shown to be an important factor in long term weight loss.

These ideas can be explored further by the links below
 * https://europepmc.org/article/med/618431
 * https://www.hindawi.com/journals/jobe/2011/482564/