Wednesday, February 23, 2011

The Biology of Obesity

Obesity in the United States has reached staggering proportions where 34% of the population is considered to be obese. The measure of obesity is the so-called “body mass index (BMI) that represents the ratio between a person’s weight in pounds multiplied by 703 (a constant) over the height in inches taken to the second power – Weight (in pounds) X 703/ (height in inches) 2. For example an individual weighing 190 pounds and with a height of 66 inches would have a BMI of (190 * 703)/ (66 inches) 2 which is equal to 30.6. A BMI greater than 30 is defined as obese and a value of over 25 is considered overweight.

The BMI was originally developed by the Belgium statistician Adolphe Quetelet (1796-1874). It is important to note that this value does not measure body fat directly, but it is a useful indicator of obesity that is recognized throughout the world.

There are many factors that contribute to obesity in the American culture. This is, however, beyond the scope of this overview. We will examine, instead, what is currently understood regarding the biology of obesity. Current understanding seems to point to three different systems of the human body that contribute to obesity – namely, the nervous system –the brain, metabolism and the genetics. We will examine these in turn.

It has long been known that the areas of the brain including the hypothalamus and the brain stem are involved in regulating the feelings of hunger and fullness. In addition, current data provided by functional magnetic resonance imaging (FMRI) that allows an investigator to visualize metabolically active parts of the human brain have also implicated the so-called pleasure reward centers of the limbic system and the prefrontal cortex. It seems that overeating, in effect, mimics drug addiction. This understanding may eventually prove useful in the treatment of obesity.

It seems that some adult men and women have retained stores of brown fat from childhood. Unlike white fat, brown fat is associated with leanness and its main function seems to be the generation of heat; whereas, white fat is involved primarily in storing energy. In some ways brown fat seems to be closely related to muscle. It remains to be seen what the factors are that predispose certain individuals to retain brown fat.

Variations in twenty separate genes have been implicated in regards to obesity; however, their cumulative contribution would be too small to account for the marked prevalence of obesity in the general population. This does not preclude the contribution of environmental factors in activating or suppressing certain genes and contributing to obesity in this way. Such genetic switches have been discovered in mice, suggesting that analogous mechanisms operate in humans.

Understanding the biology of obesity is an essential step in determining the best ways to treat this growing epidemic that has become strongly associated with modern life and culture.

Wednesday, February 16, 2011

The Negative Impact of Loneliness on Human Health

Loneliness is a common experience in human life.  It may arise from the ordinary vicissitudes of living.  Loneliness, on occasion, confronts all individuals in all walks of life and at all stages of life.  It is a quite normal and natural phenomenon. 

However, a condition of chronic loneliness has been shown to have more serious implications.  John Cacioppo, a social psychologist from the University of Chicago, has been engaged in protracted studies regarding the biological effects of a chronic state of aloneness.  As a result of his numerous investigations, he, with the help of his collaborators, has discovered changes that occur in the cardiovascular, immune and nervous systems in chronically lonely individuals.  In fact, it has been well established that individuals suffering loneliness have increased mortality.

Cacioppo has been involved in the study of the human brain's role in social behavior and is, in fact, credited with being a founder of the discipline of social neuroscience.   As a result of his extensive studies into loneliness, he has come up with some very important findings.

It is the perception of loneliness that seems to be more important than the number of social contacts a person may have.  This perception has definitive physiological impacts that adversely affect health.  It seems that lonely people have an activated sympathetic nervous system; this system is involved with the flight or fight response.  The neuro-transmitters that are produced as a result of this response, epinephrine and cortisol, lead to the constricting of blood vessels that increase blood pressure and put added stress on the heart.  In addition, the subjective feeling of loneliness impacts the immune system, resulting in an increase in the inflammatory response – implicated in heart disease – and a decrease in the capability of the body to fight viral infections.   It has also been reported that the area of the brain, the ventral striatum, implicated in the brain's reward circuitry has been shown to have decreased activity in lonely people as compared to "normal" controls.  Some genetic susceptibility to this state of mind has also been shown.

These data strongly suggest that loneliness has an adverse impact on the quality of life and the general health of those who suffer from it.  It is somewhat troubling that modern life seems to make individuals even lonelier.  The current estimate – as compiled by the U.S.  Census Bureau - is that 29% of the population lives alone; this represents a 30% increase from 1980.

Monday, February 7, 2011

Global Impact of the Rising Sea

There are many complex and interrelated facets to the consequences that result from the increasing level of Carbon Dioxide (CO2) in the earth’s atmosphere. A common misconception is that the apparent increases in the severity of winter in many parts of the United States refute the urgent need to introduce public policy that would seriously control CO2 emissions. Quite to the contrary, dramatic changes in climate that are evidenced throughout the world reinforce the serious nature of the impact of the accelerated release of green house gases into the atmosphere on global climate.

One of the more disturbing consequences of climate change is the potential for a significant rise in the sea level. Of particular interest are the consequences an increase in the sea level would have on the inhabitants of the Mekong Delta in Vietnam. This area is inhabited by 18 million people - a number that represents 22 percent of the entire Vietnamese population and accounts for 40 percent of the country’s cultivated land. In this fertile region, food production accounts for more than half the rice, 60% of the fish and shrimp and 80% of the fruit crop for the entire nation.

This area is especially vulnerable to sea level rise. Periodic flooding has played a significant role in the life of the peoples of the Mekong Delta. As a matter of fact, flood depths from a half a meter to three meters represent what is considered to be within the normal range. Such a level of flooding is referred to “nice floods” by those living in the area. However, more severe flooding can have a dramatic impact on the ability of the residents to cope.

In fact, both the frequency and magnitude of the flooding that exceeds four meters have increased. As a consequence, Individuals and families from this region are making the decision to seek another livelihood, preferably in the cities.

Using computer modeling, it has been estimated that one meter rise in sea level would impact seven million people living on the delta and a two meter rise would adversely affect fourteen million people – 50 percent of the delta population. Although current models for sea level rise do not anticipate such dramatic increases, unforeseen possibilities such as the accelerated melting of land-locked on Greenland and West Antarctic could dramatically change these predictions.

Given this information, it would be advisable for governments throughout the world to formulate policies with the purpose of curtailing the outpouring of CO2 into the atmosphere.