Okay, so here is a very simple formula for everyone. Simply counting calories will not lead to loss of body fat. The heat liberated from a particular food, whether it is fat, protein, or carbohydrate, is determined by its particular molecular structure, and this structure determines its thermic effect. The higher the thermic effect of any particular food, the higher the metabolic rate will be. Know what the body is consuming; and, more importantly, know how the body will use the consumed calories.
A method of determining the mix of fuels being utilized in the body is called the respiratory quotient (RQ), which provides a way to measure the relative amounts of fats, carbohydrates, and proteins being burned for energy.
The respiratory quotient (RQ) is the ratio of the volume of carbon dioxide expired to the volume of oxygen consumed. Because the amounts of oxygen used up for the combustion of fat, carbohydrate, and protein differ, differences in the RQ indicate which nutrient source is being predominantly used for energy purposes. The formula for calculating RQ is as follows:
The RQ for carbohydrate is 1.0, whereas the RQ for fat is 0.7. Fat has a lower RQ value because fatty acids require more oxygen for oxidation than the amount of carbon dioxide produced. The RQ for energy production from protein is about 0.8. The average person at rest will have an RQ of about 0.8; however, this result is from using a mixture of fatty acids and carbohydrates, not the protein itself, for energy production. Remember, proteins (broken down into amino acids) are not usually used for energy. In a normal diet containing carbohydrate, fat, and protein, about 40to 45 percent of the energy is derived from fatty acids, 40 to 45 percent from carbohydrates, and 10 to 15 percent from protein. However, this rate of energy production varies based on diet, physical activity, and level of physical training.
branched-chain amino acids (BCAAs): The amino acids L-leucine, L-isoleucine and L-valine, which have a particular molecular structure that gives them their name and comprises 35 percent of muscle tissue. The BCAAs, particularly L-leucine, help increase work capacity by stimulating production of insulin, the hormone that opens muscle cells to glucose. BCAAs are burned as fuel during highly intense training and at the end of long-distance events when the body recruits protein for as much as 20 percent of its energy needs.
In general, physical conditioning lowers the RQ, which means more energy is being obtained from fatty acids in the trained individual. However, more energy is also being obtained from protein in the trained individual. Carbohydrate is always being used for energy. For example, in a study comparing the RQ of untrained versus trained individuals during exercise, the RQ of the untrained individuals was 0.95 and the RQ of the trained individuals was 0.9. This means that while both groups were using mostly carbohydrate for fuel during exercise, the trained individuals were using a higher amount of fatty acids for energy. At rest, fatty acids are the predominant energy source in most people; as exercise begins, carbohydrate utilization increases. High-intensity exercise uses more carbohydrate, while low- to moderate-intensity exercise uses fatty acids and carbohydrate for energy. Of course, these ratios change when one consumes only fats and proteins and no carbohydrates as fuel.
While this discussion of RQ is very brief, you can see that the energy substrate utilization of the body is quite varied, and both composition of the diet and intensity of physical activity determine which energy substrates are used. Therefore, it is easy to see why different sports require different dietary considerations.
A method of determining the mix of fuels being utilized in the body is called the respiratory quotient (RQ), which provides a way to measure the relative amounts of fats, carbohydrates, and proteins being burned for energy.
The respiratory quotient (RQ) is the ratio of the volume of carbon dioxide expired to the volume of oxygen consumed. Because the amounts of oxygen used up for the combustion of fat, carbohydrate, and protein differ, differences in the RQ indicate which nutrient source is being predominantly used for energy purposes. The formula for calculating RQ is as follows:
The RQ for carbohydrate is 1.0, whereas the RQ for fat is 0.7. Fat has a lower RQ value because fatty acids require more oxygen for oxidation than the amount of carbon dioxide produced. The RQ for energy production from protein is about 0.8. The average person at rest will have an RQ of about 0.8; however, this result is from using a mixture of fatty acids and carbohydrates, not the protein itself, for energy production. Remember, proteins (broken down into amino acids) are not usually used for energy. In a normal diet containing carbohydrate, fat, and protein, about 40to 45 percent of the energy is derived from fatty acids, 40 to 45 percent from carbohydrates, and 10 to 15 percent from protein. However, this rate of energy production varies based on diet, physical activity, and level of physical training.
branched-chain amino acids (BCAAs): The amino acids L-leucine, L-isoleucine and L-valine, which have a particular molecular structure that gives them their name and comprises 35 percent of muscle tissue. The BCAAs, particularly L-leucine, help increase work capacity by stimulating production of insulin, the hormone that opens muscle cells to glucose. BCAAs are burned as fuel during highly intense training and at the end of long-distance events when the body recruits protein for as much as 20 percent of its energy needs.
In general, physical conditioning lowers the RQ, which means more energy is being obtained from fatty acids in the trained individual. However, more energy is also being obtained from protein in the trained individual. Carbohydrate is always being used for energy. For example, in a study comparing the RQ of untrained versus trained individuals during exercise, the RQ of the untrained individuals was 0.95 and the RQ of the trained individuals was 0.9. This means that while both groups were using mostly carbohydrate for fuel during exercise, the trained individuals were using a higher amount of fatty acids for energy. At rest, fatty acids are the predominant energy source in most people; as exercise begins, carbohydrate utilization increases. High-intensity exercise uses more carbohydrate, while low- to moderate-intensity exercise uses fatty acids and carbohydrate for energy. Of course, these ratios change when one consumes only fats and proteins and no carbohydrates as fuel.
While this discussion of RQ is very brief, you can see that the energy substrate utilization of the body is quite varied, and both composition of the diet and intensity of physical activity determine which energy substrates are used. Therefore, it is easy to see why different sports require different dietary considerations.