More specifically, when certain species (including homo Sapiens) consume more calories than necessary for immediate energy requirements, their digestive systems efficiently converts those excess calories into storable forms of reserve energy that are capable of being called upon in times of need (Larson-Duyff, 2005; Rinzler, 2004). In humans, excess caloric consumption increases the amount of sugars dissolved in the blood (Larson-Duyff, 2005; Rinzler, 2004). This triggers a natural insulin response in which the pituitary signals the body to release extra insulin into the bloodstream to process the blood sugar. Many chronically overweight individuals become resistant to insulin, eventually requiring artificial insulin supplementation to maintain blood sugar levels consistent with ordinary physiological processes and to avoid onset of acute diabetic responses that are debilitating and that can be fatal when not treated appropriately (Hamric, Spross, & Hanson, 2009; Taylor, Lillis, & LeMone, 2005).

Even in non-diabetics, excess blood sugar attributable to consumption of more calories than necessary for energy production results in the storage of excess body fat through similar mechanism (Larson-Duyff, 2005; Rinzler, 2004). Ordinarily, blood sugar is converted by the liver into glycogen, which is stored both in the liver as well as in the muscle tissues where it can be called upon as a reserve energy source. However, once the body's glycogen storage has reached full capacity, additional consumption of calories triggers a longer-term storage mechanism whereby they are converted into body fat. This evolutionary adaptation was absolutely necessary for survival in evolutionary periods; today, however, it is no longer necessary in developed nations and it is the primary physiological mechanism responsible for obesity as a result of chronic overeating (Larson-Duyff, 2005; Rinzler, 2004).

Typically, the American diet consists of too many calories, too much dietary fat, too much high-calorie sugar and sugar-like sweeteners (such as high-fructose corn syrup), and too much sodium which also has detrimental effects on cardiovascular and cardiopulmonary health (Hamric, Spross, & Hanson, 2009; Taylor, Lillis, & LeMone, 2005). Excess dietary fat consumption is also a cause of excess cholesterol, another significant risk factor in the development of cardiopulmonary dysfunction by virtue of the reduction blood flow to the heart attributable to arterial plaque buildup within the walls of major blood vessels. It is also a cause of fatty tissue deposits on the major organ, including the heart, which only increases its load and its inefficiency as well (Hamric, Spross, & Hanson, 2009; Taylor, Lillis, & LeMone, 2005).

In terms of conversion to excessive body fat, certain foods are much more conducive to being converted into fat than others; unfortunately, they are also the very foods consumed most irresponsibly, simply because they happen to be the most palatable. Specifically, foods high in fat content are the most readily converted and stored from their nutrient state to body fat because they require the least energy input into breaking down their molecules and because they are already molecularly most similar to the composition of stored body fat (Larson-Duyff, 2005; Rinzler, 2004).

Sugars and simple carbohydrates (such as highly processed white rice, ordinary potatoes, and bleached white flours and grains) are also readily converted into blood sugar and then stored as body fat because their simple molecular structure requires comparatively little energy to break and convert into stored body fat (Larson-Duyff, 2005; Rinzler, 2004). Conversely, more complex carbohydrates (such as brown rice, sweet potatoes, and unbleached whole grain flours and grains) require significantly more energy to break their more complex molecules and they are more readily converted into glycogen than absorbed and converted into fat in the manner of simpler carbohydrates after being dumped into the bloodstream (Larson-Duyff, 2005; Rinzler, 2004).

Because food manufacturers always seek to generate the most revenue from their products, they have learned to rely heavily on the use of sugars, simple carbohydrates, and fats, simply because those foods are the most palatable to consumers and therefore, result in much greater sales than healthier foods that are not as satisfying (Lightsey, 2006; Sizer & Whitney, 2003). Fast foods are particularly notorious in that regard, especially in light of the degree to which and the manner in which they are marketed directly to children. Empirical evidence has established that children who become overweight or obese prior to adulthood have exceptionally high chances of remaining overweight or obese throughout their adult lives (Hamric, Spross, & Hanson, 2009; Taylor, Lillis, & LeMone, 2005).

In fact, in the U.S., more than two-thirds of families now spend more money on prepared foods (i.e. restaurant food) than they spend at the grocery store (Baldauf, 2008; Gibbs, 2007). Second, fast-food franchises are so ubiquitous and so heavily (and effectively) promoted and advertised that there is a significant peer-pressure factor that makes it even more difficult to steer children away from fast foods. Adults also develop nutritional habits that are highly detrimental to their health, often partly because of the convenience factor.
Unfortunately, the national epidemic of overweight and obesity has generated a multi-billion dollar weight loss product industry as well. That severely complicates the problems already faced by individuals who are overweight and obese, largely because it promotes unhealthy rapid weight loss over the short-term and through artificial means (such as fad diets) that cannot possibly be maintained over the long-term (Lightsey, 2006; Sizer & Whitney, 2003). In principle, losing excess weight and repeatedly regaining it is much more detrimental to long-term weight maintenance and health, primarily because this pattern of "yo-yo" weight loss actually increases the individual's percentage of body fat during each and every cycle of weight loss and regain (Lightsey, 2006; Sizer & Whitney, 2003).

The mechanism responsible for that phenomenon is very simple. First, virtually any means of drastically reducing caloric intake will result in dramatic weight loss (Larson-Duyff, 2005; Rinzler, 2004). However, no such diet that limits the individual to a very narrow range of foods or that entirely eliminates all carbohydrates (for one example of a popular diet fad called the Atkins Diet) can possibly be sustained for life. At most, such diets allow dieters to lose large amounts of weight and to keep it off for several weeks, months, or sometimes, several years, although even that is quite rare (Lightsey, 2006; Sizer & Whitney, 2003). In virtually one-hundred percent of cases, dieters who lose weight by these types of gimmicks always regain all of their weight within several years, and the vast majority of them do so much sooner, typically in less than one year (Lightsey, 2006; Sizer & Whitney, 2003)

The problem is that each and every time that they lose substantial amounts of body weight and then regain it, they actually increase their overall percentage of body fat (Lightsey, 2006; Sizer & Whitney, 2003). The reason is very simple: when body weight is lost quickly, it usually consists of roughly equal amounts of fat and non-fat body tissues (i.e. muscle tissue). Conversely, when body weight is gained quickly by overeating, it is almost entirely fat and not muscle or any other tissue. As a result, each time a dieter loses a given amount of weight quickly, he or she loses substantial amounts of non-fat tissue. Then, when the weigh is regained, it is almost all in fat. In effect, each cycle of rapid weight loss followed by its regain actually replaces some muscle tissue with body fat, thereby increasing the individual's overall body fat percentage in addition to merely regaining the amount of weight as measured in pounds (Lightsey, 2006; Sizer & Whitney, 2003). Ultimately, the continual increase in weight and in body fat percentage only further impedes the ability of the individual to participate in physically strenuous activity or exercise, which only contributes even more to the problem of obesity.

Physical Activity

Everything else being equal, physically active individuals are much less likely to become overweight or obese than individuals who are comparatively physically inactive (Hamric, Spross, & Hanson, 2009; Taylor, Lillis, & LeMone, 2005). The fact that contemporary society has become so much more sedentary, therefore, also contributes greatly to the phenomenon of obesity epidemics. Whereas previous generations worked in manual labor capacities and typically walked comparatively long distances back and forth from work or school, that is no longer the case in much of the developed world (Jackson, Al-Mousa, Al-Raqua, et al., 2001).

Today, the majority of vocational employment involves sedentary office jobs instead of physical labor of the type that was much more common as recently as a half century ago. Likewise, modern public transportation systems and the widespread reliance on automobiles has greatly reduced the need for walking or bicycling among adults. Consequently, many adults get very little physical exercise of any kind. Naturally, that is a dangerous combination…