A whole-body metabolism simulation model
Miyagi Respratory and Cardiovascular Center
Last modified: March 20, 2006
Obesity is now epidemic in the US. There are great many fad diets and also there is a wealth of conflicting evidence supporting claims that each is better than the others. There seems no clear way to determine which one is best suited for a particular individual. We will introduce a whole-body metabolism simulation model, which will be used to predict the body weight change expected for each combination of diet, exercise, and initial body state. There are three major energy-providing categories in diets: protein, carbohydrates, and fat. Daily protein turnover triggers energy production for the body. This process is affected by external energy demands such as exercise. Carbohydrates are the primary energy resource for brain function under normal conditions. Protein and carbohydrate can share their carbon skeleton. Adequate carbohydrate intake can save further protein consumption. Any excess of carbohydrates must be burned or converted into fat due to limited storage. The body uses fat to store energy. More than 97% of stored fat is triglyceride, consisting of glycerol and fatty acids. Glycerol can be converted into carbohydrate, but fatty acids cannot. This inequality of macronutrients is what tends to cause fat accumulation. Hormonal network coordinates this systemic metabolism. While this system is too complex to describe all its pathways, the outcome is simpler; to preserve existing metabolic active protein and to store any excess of energy as fat. We then focused on the macronutrient dynamics to further develop our model. We are in the process of testing the validation of our model base on clinical data collected in our hospital and utilizing the published literature. We have found our model to be partly inadequate, but it is quite certain that it will give us an insight into hidden metabolic dynamics through this process.