Severe obesity

Severe Obesity: Evidence for a deranged Metabolic Program in Skeletal Muscle?

Journal of Exercise and Sport Sciences, Volume 40 (4), October 2012, p 204-210.

A Review and Summary

            There are many health complications associated with being obese and, I believe, that as an understanding of how damaging obesity is to the body, medical science is just beginning to scratch the surface.  To this point most of the research has focused on understanding and managing health risk factors such as the levels of blood pressure, cholesterol, blood glucose, and triglycerides to name a few.  To my knowledge, few research studies have been conducted to understand the efficiency with which obese people metabolize or ‘breakdown’ stored body fat to be used as a source of energy.  This study had a very broad scope and not all of the information included in this particular study will be discussed here.  Specifically, this review will be focused on the findings regarding fatty acid oxidation, which is one of the energy systems used to break down body fat.

            Before getting into the specifics of this study’s findings a basic understanding of how the body provides itself with energy during exercise.  This process is far more complex than described here, but for the sake of simplicity only the very basics of the process will be discussed.  Inside of every individual muscle cell is a naturally occurring biochemical compound call ATP-Cr.  The energy released from this compound causes muscular contraction during exercise.  This compound is a stored form of energy that the body keeps supplied within the muscles ready to be used at a moment’s notice.  However, the body is only capable of storing enough of this compound to fuel about 15 seconds of intense physical activity.  It takes a rest period of 45 seconds to one minute for the muscles to restore the levels to be driven through this primary energy system.  If physical activity is to continue longer than 15 seconds energy for this ATP-Cr compound must be restored from another source.  This is accomplished through what it called the glycolytic system which manufactures the ATP-Cr compound by breaking down the glycogen within the muscle cell.  Glycogen is the name given to the amount of glucose stored within muscle cells.  This process is a little slower than the initial ATP-Cr system.  Exercise supported by this energy system cannot be maintained at as high of intensity as the first system. Furthermore, the muscle cells can only store enough glycogen to support about 2 minutes of exercise.  This lead into the third and final energy system; fatty acid oxidation.  Again, this energy system is about replenishing the ATP-Cr levels within the cell, and yes, as the name suggests, it does this through the breakdown of stored body fat, converting it into fatty acids which are transfer to the liver.  At the liver, the fatty acids are converted into glucose, which travels to the muscle cells and becomes muscle glycogen.  This glycogen is then used to make more ATP-Cr.  As you have probably guessed from the description this process is even slower.  In fact, it is the slowest method of providing the muscles with energy and it only comes into play when the first two systems have run their course.  Again, because this is slower the intensity of exercise that can be maintained is lower than that which can be achieved through the two previous energy systems.  This oxidation system really only comes into play during slow pace, endurance events.  Energy from this system will support the body for up to two hours, depending upon intensity, before the body must consume calories to continue having adequate energy levels.

            It is time to focus on the research findings of the study.  The purpose of this study was to identify whether or not there is a difference in the efficiency of the use of the fatty acid oxidation system between obese people and those of healthy body weight.  This was accomplished through using three groups of people: healthy weight, BMI averaged 23.8; obese BMI average 30.2, and severely obese BMI average of 53.8.  The method used for this was to measure the amount of carbon dioxide released from the muscle cells of the rectus abdominus during exercise.  Carbon dioxide is a chemical by-product of muscular contraction.  The rate at which it is produced can be used as an indicator for the efficiency of energy production within the muscle cells.

            One of the most interesting findings from this study is that there was no difference in the efficiency of fatty acid oxidation between the groups of healthy 23.8 BMI and obese people of the 30.2 BMI group.  So, it would seem that the bodies of those who are obese, but only just heavy enough to be considered obese, can metabolize body fat for energy just as well as those that are of healthy BMI, provided that the obese group exercises.  However, the severely obese, 53.8 BMI group, on average, used this fatty acid oxidation at a rate approximately 60% less efficient than the other groups.  Or, it can be considered that the severely obese group metabolized body fat with only 40% of the efficiency that the healthy and obese groups.  It should be noted that after these initial findings the study conducted intervention assistance using nutritional counseling, exercise counseling, or a combination of both.  The group that underwent both the exercise and nutrition counseling saw the greatest improvement through weight loss and improved fitness.

            So how does the affect structuring an exercise program for the severely obese to maximize weight loss?  Start by understanding that any exercise is better than no exercise. Slow duration, low intensity, endurance exercise is not the most efficient way to lose weight but for those who are severely obese it is generally the safest and easiest way to begin.  Start by focusing on building up the endurance until you are able to 30 minutes of continuous cardiovascular exercise without needing to stop to rest.  After reaching the 30 minute mark start strength training.  Perform this on any cardio piece; treadmill, bike, or elliptical.  For strength training, perform one set of an exercise for the back chest, shoulders, arms, and legs.  Focus on learning the fundamentals of the motion.  After two weeks complete two sets of each exercise and add a third set after one month.  Workout Twice a week with weights for the first month and perform cardio four days per week.  Starting in the second month add a third weight training session each week.  This is a basic plan meant to lay a foundation to build upon.  Gradually increase the cardio by 5 minutes a week until you a performing a full hour of cardio.  The weight loss will be slow with this program, especially without strict control of the diet.  Remember, at the beginning of the program the purpose of exercise is to improve physical endurance and the ability to move so that the body is prepared for more intense exercise later.