Changes in Body Composition

Body composition changes. We can influence that change by taking charge of what we eat and how we exercise. The general rule for lean mass (including bone mass) is"use it or lose it."We've wonderfully adaptive creatures, and we quickly adapt to our environments and our activities. We know, for instance, that the bones of astronauts quickly demineralize because the gravity-free environment of outer space eliminates the need for a strong skeleton. We would do quite well in that environment looking like a jellyfish, and the bones quickly adapt by releasing lots of calcium. The effect of this environment is so strong that astronauts must spend a significant amount of time doing exercise that places stress on the skeleton. Again, we've adaptive creatures, so placing this artificial stress on the bones helps keep them strong, even in a gravity-free environment. The same thing happens when people are bedridden because of an injury. Both bone and muscle masses are rapidly reduced because they simply aren'tneeded when you've lying in bed. The important thing to remember about our tissues is that they are alive and will do what's needed to adapt to their current situation. Even bone, which to the casual observer might appear to be a hard, rocklike, nonadaptive structure, is actually very much alive and changing itself all the time. Minerals move in and minerals move out, and this process leads to a constant remodeling of bone.

When you consider the influences on body composition, they boil down to the following:

• Genetic predisposition. This is everyone's bottom line, and no matter how hard you try, you can't change it. People have different inherited body types, and each type has a different predisposition toward accumulating more or less fat. Endomorphs (large trunk, short fingers, shorter legs) have a predisposition toward higher body fat percentages, and ectomorphs (long legs, long fingers, shorter trunk) have a predisposition toward a slender build with less body fat. What you've born with can't change, so all you can hope to do is optimize what you've been given.
• Age. People generally develop a lower lean mass and higher fat mass after the age of 30. However, although this age-related change in body composition is normal, it isn't inevitable. It has been clearly shown that a good diet and regular activity can keep you lean. Since energy metabolism drops about 2 percent for each decade after age 30, it gets progressively more difficult to maintain a desirable weight and body composition. To maintain what you've got, you would have to make either a 2 percent increase in energy expenditure or a 2 percent decrease in energy intake each decade after 30 to match the drop in energy metabolism. Although this 2 percent difference seems small, it could make a major difference in your body composition. Consider that the average person consumes about 2,500 calories per day. If you need 2 percent less than this and don't make an adjustment, that represents a 50-calorie error of excess each day. Multiply that over 365 days and it represents 18,250 excess calories per year. Since an excess of 3,500 calories represents a 1-pound weight gain, in the course of 1 year this small 50-calorie error would manifest itself as a weight gain of more than 5 pounds (2.3 kilograms). In 5 years, that's a weight gain of 25 pounds (11.5 kilograms), and in 10 years, that's a weight gain of a whopping 50 pounds (23.0 kilograms).
• Gender. All other things being equal, women have a higher body fat percentage than do men. Nothing can be done to alter this, and there is certainly nothing wrong with it. The gender difference is just a manifestation of the different biological expectations of men and women. However, there are many women who have a lower body fat percentage than some men because they exercise more and eat better. Therefore, despite this baseline difference, doing the right things can help you (regardless of your gender) optimize your body composition for your sport.
• Amount of activity. Clearly, the more a person exercises, the greater the potential benefits in desirably altering body composition. However, activity must be supported by an adequate intake of energy. Increasing the time of activity without also increasing the amount of energy intake causes a breakdown of muscle mass to support energy needs. There is no question that this would be an undesirable change in body composition for an athlete. In addition, overtraining, although it will not necessarily lead to a reduction in lean body mass, causes an increase in muscle soreness and reduces muscular power and endurance. Therefore, the amount of activity should be carefully balanced with adequate energy intake and with adequate rest to ensure maintenance of muscle mass and athletic performance.
• Nutrition. Eating too much or too little can both negatively affect body composition. Eating too much, either over the course of a day or at one time, is likely to increase fat storage; eating too little will lower both lean (muscle) mass and fat mass. In addition, certain nutrients are important for metabolic processes. A failure to consume an adequate level of these nutrients (B vitamins, zinc, iron, and so on) may reduce your ability to properly burn fuel, thereby limiting your ability to burn fat through exercise.