Exercise as it relates to Disease/Effectiveness of different modalities of exercise on metabolic regulation in obese adolescent boys
It is of no doubt that the prevalence of overweight and obesity is rapidly growing. This trend is seen in both economically developed and developing areas around the world. Epidemiological studies have consistently made it clear that being overweight and obese, specifically abdominal obesity, are strong risk factors for obesity related comorbidities such as cardiovascular disease, cancers and insulin resistance, a key feature for such cardiometabolic diseases as well as type II diabetes.
Insulin resistance is a condition in which the insulin produced by the body becomes ineffective therefore the individual is unable to absorb the glucose into the cells and remains in the blood stream. This can cause a cascade of effects, ultimately leading to impaired insulin secretion and consistent elevated glucose levels, a strong indicator for type II diabetes. Higher risk individuals are generally;
Modalities of Exercise
Physical activity can provide health benefits for obese adolescents however the question still remains, which modality of exercise is the most optimal for reducing obesity related comorbidities in adolescents.
Studies have reported that following an aerobic exercise protocol can show greater improvements in ones insulin sensitivity compared to resistance training. Further, studies have demonstrated improvements in insulin sensitivity are similar for resistance and aerobic exercise, and showed no significant difference in improvements for those that dieted alone 
Therefore the aim of this study was aimed to compare the effectiveness of different modalities of exercise, resistance versus aerobic, without caloric restriction on abdominal fat, ectopic (liver) fat and insulin regulation in obese adolescent boys.
The Current Study
Where was the research from?
This research was from the American Diabetes Association.
What kind of research was this?
The current study was a 3-month randomized, controlled trial investigating the effects of exercise modalities on insulin regulation. When done correctly, a randomized control trial can be viewed as the gold standard for assessing healthcare interventions. The study consisted of three different exercise groups;
- Aerobic exercise (AE)
- Resistance exercise (RE)
- Non exercise control group
What the research involved
The investigation included 45 participants that were pubertal (ages 12–18), non-diabetic and physically inactive. The study excluded any adolescents who have participated in structured exercise outside of school or have had any significant weight changes (change in BMI>2–3 kg/m2). This ensured that there was minimal variance amongst subjects, which could potentially obscure results. Participants were asked to complete a number of assessments prior, during and post intervention;
- An oral glucose tolerance test was used to obtain glucose and insulin levels were obtained after an overnight fast with a minimum of 8 hours.
- Measurement of insulin sensitivity was assessed using the glucose clamp method. This method is cited as the reference standard and provides a direct measure of insulin sensitivity.
- Whole body magnetic resonance imaging was used to measure adipose tissue, skeletal muscle and visceral and abdominal subcutaneous fat.
- Intrahepatic lipid were assessed by proton magnetic resonance spectroscopy, another technique that has been cited to accurately reflect the severity of a fatty liver.
Dietary Regime: Subjects were required to follow a diet regime at maintenance calories (55-60%CHO, 15-20%%PRO, 20-25%FAT). Anytime a participant deviated away from the original weight (>4%) for two weeks their nutrition was looked at to identify the change. Therefore, this allows for any changes that occurred were related to physical activity not a decreased caloric intake.
Exercise Regime: The aerobic group was required to exercise three times per week for 60 minutes at 60-75% of VO2 Max. Although it is has been recommended that overweight/obese individuals should seek to perform >210minutes of exercise per week, significant effects on body composition (body fat) can be achieved through lower dosed exercise regimes than that which is currently recommended.
The Resistance group was required to perform 10 whole body exercises three times per week for 60 minutes also. Similarly, the most optimal resistance training approach to improve ones insulin sensitivity is unknown. However, literature has stated that improvements in amount and quality of skeletal muscle are key mechanisms for improving glucose regulation. This study used an exercise program that was indirectly progressive, which ultimately leads to continuous muscle protein adaptations including quality and quantity.
Thus, it is clear that appropriate methods were used in this study improving the quality of this investigation.
Both aerobic and resistance exercise performed for 180 minutes can significantly reduce levels of total fat, visceral fat, intrahepatic fat and improve cardiorespiratory fitness in obese adolescent boys.
- Resistance but not aerobic exercise was associated with greater significant improvements in insulin sensitivity, skeletal muscle mass and muscular strength.
- The resistance exercise group showed a minor yet significant decrease in BMI compared to the aerobic group.
- Both exercise groups showed significant improvements in cardiorespiratory fitness.
Interpretation of the results
- The findings of this study provide very important health implications and help demonstrate therapeutic strategies for treating childhood obesity and its related cardio-metabolic diseases.
- Irrespective of modality, engagement of consistent exercise can promote significant reductions in intrahepatic lipid, an important factor as increased liver fat is a strong association with insulin resistance.
- Previous studies have reported that improving aerobic fitness and skeletal muscle mass are important factors for improving insulin sensitivity. Therefore this could partly rationalise the improvements in insulin sensitivity observed in the resistance group.
Implications and Conclusions
- The results of this investigation has made it clear that engaging in physical activity leads to significant health benefits in obese adolescents.
- It provided information about how certain modalities of exercise can result in different outcomes. For instance, compared to the aerobic group, there were greater improvements in insulin sensitivity and slightly greater improvements for BMI observed in the resistance group.
- This study and other investigations have also outlined the role resistance training has for preserving and developing skeletal muscle mass which is an important component in regulation of such metabolites.
- Skeletal muscle mass is also a key determinant in resting metabolic rate, a decline in lean tissue can typically be observed during periods of weight loss.
- A decrease in lean body tissue can inhibit the progress of weight loss. Therefore, development and preservation are important factors to consider when designing therapeutic interventions for obese adolescent boys during weight loss
- This investigation and other studies have reported higher energy expenditure, greater reductions in weight and body total fat in shorter-term (<4 months) interventions compared to longer-term (>6 months) studies. The question remains as to whether the positive effects and compliance can be sustained for longer periods of time.
- This is important to note as the body has compensatory mechanisms, which will oppose the exercise induced energy deficit. Such metabolism compensatory responses can counter the imposed energy deficit from exercise or diet. Thus it is important to have a periodised approach to weight loss. Like any other physical program, weight loss requires a systemic approach.
In summary, this investigation has provided robust information about the importance physical activity has on individuals suffering from obesity.
Weight loss can be achieved using a variety of different exercise methods, either individually or in combination. The difficulty is maintaining weight loss over a longer period of time and keeping it off.
It is imperative to design or find an exercise regime that can be adhered too. Remember, optimal is not necessarily the same as realistic. Find a physical exercise program that is sustainable for your lifestyle.
For further information on metabolic compensatory mechanisms, body composition and insulin sensitivity.
- Identification of compensation for exercise induced weigh loss: http://www.nature.com/ijo/journal/v32/n1/abs/0803712a.html
- An energy balance analysis, implications for the individual: http://onlinelibrary.wiley.com/doi/10.1111/j.1467-789X.2012.01012.x/full
- Body composition and insulin sensitivity: http://diabetes.diabetesjournals.org/content/32/10/965.short
- Comparison of resistance and aerobic training in RMR: http://ajcn.nutrition.org/content/66/3/557.short
- For the interest of the individual. Purchasable E-books providing guidance, information and practical advice for nutrition and training: http://muscleandstrengthpyramids.com
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