Nearly everyone today worries about being overweight. Images from television and the internet promote what is sometime an unhealthy obsession with low body weight. We're constantly inundated with messages about widespread obesity and the risks that accompany obesity. Whether it is due to health issues or social acceptance, no one wants to be fat.
Looking at it from an evolutionary perspective however, the ability to store excess calories in the form of fat cells is a very life-serving ability. The body stockpiles energy in the form of fat when times are easy and food is plentiful so that it can use this energy to survive when food is scarce. For our ancient predecessors, this was a survival mechanism that allowed the species to survive during harsh conditions. When a person consumes more calories than the body uses for muscle movement, internal temperature maintenance, and cellular repair (amongst other things), the remainder is stored in the chemical bonds of fat cells. Technically, it is stored in something called “adipose tissue”. Energy isn't a physical substance, so it's not the same thing as fat. It becomes available for use when fat molecules break down into simpler products. This occurs when a person increases movement or otherwise triggers the need for more energy.
Carbohydrates are a major source of that energy. Sugars (chiefly glucose) and starches are the two main forms, and they participate in something that is known as the Krebs Cycle. Also known as the tricarboxylic acid cycle, this is the process whereby sugars are broken down into ATP, and then into ADP. Energy is released during this process.
When the body runs out of readily available glucose to use in the cycle, it turns to stored body fat as a substitute. Breaking down these fat molecules is, in essence, what causes a person to decrease the percentage of body fat. If increased muscle mass occurs due to vigorous physical activity the result is not always net weight loss.
In biology, as in life, everything is best in moderation. When more calories are consumed than used over a long period of time, body fat increases to the point that the health risks can outweigh the benefits of a ready supply of energy. Real medical problems can occur, heart difficulties and diabetes being just two. Of course, the social consequences are equally distressing.
Many people strive to maintain their weight in order to avoid increased health risks associated with obesity. The ideal range that body fat should fall into differs from person to person (because of different body types), season to season (moderate winter fat can actually be healthy), and according to their individual BMI (Body Mass Index). In order to ascertain whether you classify as obese, or whether you may just be moderately overweight, or in fact whether you just lack muscle tone, you need to consider these factors. This requires a knowledge of your specific body type, the ability to calculate BMI (very simple formula), and recognizing that there is no exact ideal weight that is static.
