Exercise as it relates to Disease/Effect on exercise intensity on fat loss in obese and overweight postmenopausal women
This page is a critical analysis on the article "Effect of exercise intensity on abdominal fat loss during calorie restriction in overweight and obese postmenopausal women: a randomized, controlled trial" by Nicklas BJ, Wang X, You T, et al.
What is the background to this research?
The prevalence of global obesity in both adults and children is increasing dramatically, this is of concern as it may result in numerous negative implications such as type II diabetes, cancer, high blood pressure, heart disease, stroke and an overall poorer quality of life. Obesity numbers increase with age and peaks amongst middle-aged and older women. This age group and gender is effected by menopause, which can be associated with an increased risk of weight gain and thus obesity. Menopause results in a body composition shift due to a decreased level of oestrogen circulating in the body, where body fat from the gluteofemoral region will be redistributed to the abdominal region.
The general consensus is that diet and exercise are effective strategies for losing excess abdominal fat, but it is how the individual carries out this protocol that effects how much total fat will be lost. A greater total volume of exercise performed will result in increased fat loss. However, there is generally no indication of how intensity should be factored into exercise even though it has been shown that vigorous intensity has resulted in greater improvement in risk factors of CVD. This could mean that varying intensities could result in different outcomes when measuring fat loss.
Where is the research from?
The research was conducted by a team based out of Wake Forest School of Medicine and Wake Forest Baptist Health which are apart of the Wake Forest University in North Carolina, United States. The team has extensive experience with clinical trials and many publications relating to health. The authors had no potential, real or perceived conflict of interest. The article was funded by the Wake Forest University and published in the American Journal of Clinical Nutrition in February of 2009.
What kind of research was this?
The research was conducted using a randomized controlled trial. This method was chosen as it is a highly regarded method to test efficacy and effectiveness of many different types of interventions. In this instance participants were assigned different interventions randomly which minimises bias that other methods may incur. The controlled aspect relates to one group being assigned to an intervention where what is being measured is just a standard practice, a placebo or nothing at all. The randomized aspect of this study was the intensity of the exercise and the controlled aspect was the caloric deficit.
What did the research involve?
The research involved randomly assigning 112 overweight or obese postmenopausal women classified by a BMI of 25-40 and a weight circumference of more than 88 cm to one of three 20 week interventions. All interventions featured a caloric deficit which was around 400 Kcal/day; 2800 Kcal/week. The first intervention was just a caloric deficit, the second featured a caloric deficit and moderate intensity aerobic exercise and the third intervention contained a caloric deficit and vigorous intensity exercise. Exercise was 3 days a week where participants would walk on a treadmill either at 45-50% of heart rate reserve which was classified as the moderate intensity exercise or they would walk at 70-75% of their heart rate reserve, and this was classified as the vigorous exercise. Dietary intake, body composition, abdominal fat and VO2 max were the main variables measured at baseline and after the 20 week interventions.
What were the basic results?
At the conclusion of the 20 week intervention the following results were recorded where 17 individuals did not adhere to the program so results are based off of 95 participants:
- Daily energy intake needed for weight maintenance saw a 19-20% reduction (for the exercise groups) and a 23% reduction (for the caloric deficit group).
- The average weight loss for all women was 12.1 ± 4.5 kg, with the range of weight loss being 1.2–23.1 kg. CR only: 36.2 ± 17.1%; CR + moderate-intensity: 27.7 ± 14.8%; CR + vigorous-intensity: 26.7 ± 12.1%.
- VO2 max expressed per kilogram of body weight increased significantly; CR only: 9.6 ± 11.2%; CR + moderate-intensity:12.7 ± 12.7%, CR + vigorous-intensity: 24.2 ± 27.6%.
Improvements were seen across everything that was tested; daily energy intake decreased, visceral fat was reduced and VO2 max increased.
What conclusions can we take from this research
The objective of this study was to show if intensity of aerobic exercise affected the loss of abdominal fat of postmenopausal women. Although the results showed desired outcomes such as abdominal fat loss, this study displayed that when the energy deficit is matched, fat loss from the abdominal region is not increased as a result of varying aerobic exercise intensities.
There is existing data which shows results that exercise of higher intensity or duration can result in increased abdominal fat loss, however, this can be accounted for by the differences in energy expenditure and perhaps a flaw of this study is the large energy deficit cause by the caloric deficit of the exercising groups, so perhaps in an uncontrolled setting a larger negative energy deficit could show greater fat loss as a result of more vigorous intensity exercise.
Another flaw of the study could be the time period, if the interventions were extended longer, perhaps over a year, maybe different outcomes may have occurred where intensity contributed significantly more to abdominal fat loss.
Overall the study was conducted and structured very well with no real problems interfering with the study. Adherence to the program was very high, this could be attributed to the exercise that was being performed in walking, which obese people tend to enjoy. As the interventions were controlled with the energy intake it made the data much more reliable as all the groups were intended to have equal caloric intake relative to their exercise, therefore results couldn't be influenced by diet.
This study suggests that that there is no difference between the effects of different intensity exercise. Even though this area of varying intensities remains unclear is does clearly highlight one thing, which is that through successfully adhering to a caloric deficit diet with sufficient physical activity fat loss will follow and anyone can do it. So what it comes down to is what type of exercise the individual prefers, performing what type of exercise and intensity is preferred will likely see that individual adhere to the program longer. However beginners need to seek professional assistance before beginning any program, this could be a dietitian, a personal trainer and even a GP.
- Effect of an energy-restrictive diet, with or without exercise, on lean tissue mass, resting metabolic rate, cardiovascular risk factors, and bone in overweight postmenopausal women.
- Mobilization of visceral and subcutaneous adipose tissue in response to energy restriction and exercise.
- A meta-analysis of the past 25 years of weight loss research using diet, exercise or diet plus exercise intervention.
- The effects of exercise training on fat-mass loss in obese patients during energy intake restriction.
- Nicklas BJ, Wang X, You T, et al. Effect of exercise intensity on abdominal fat loss during calorie restriction in overweight and obese postmenopausal women: a randomized, controlled trial. The American Journal of Clinical Nutrition. 2009;89(4):1043-1052. doi:10.3945/ajcn.2008.26938.
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