Causes of Obesity

Problem 1: Diagnosing Causes For Sudden Rise in Obesity Levels
Any explanation of the root causes of the current obesity epidemic must account for its sudden appearance. Six million American adults are now morbidly obese (BMI 40+), almost twice as high as 1980 severe obesity rates, while another 9.6 million have a BMI of 35-40. The percentage of overweight children 6-11 has nearly doubled since the early 1980's. (Source: US Census 2000; NHANES III data estimates). Thus genetic causes are unlikely to be significant. Because while a predisposition to obesity can be inherited, the fact that obesity has increased so much in the last few decades appears to discount genetics as a major main cause. Also, the fact that each succeeding generation is heavier than the last indicates that changes in our environment are playing the key role.

Family Influence - A Major Contributory Cause to Obesity
Parental behavioral patterns concerning shopping, cooking, eating and exercise, have an important influence on a child's energy balance and ultimately their weight. Thus family diet and lifestyle are important contributory causes to modern child obesity, especially at a time of rising affluence. Since obese children and adolescents frequently grow up to become obese adults, it's clear that family influence also extends to adult obesity.

Genetic Causes of Modern Obesity
Genes affect a number of weight-related processes in the body, such as metabolic rate, blood glucose metabolism, fat-storage, hormones, to name but a few. Also, some studies of adopted children indicate that adopted children tend to develop weight problems similar to their biological, rather than adoptive, parents. In addition, infants born to overweight mothers have been found to be less active and to gain more weight by the age of three months when compared with infants of normal weight mothers, suggesting a possible inborn drive to conserve energy. Research has also shown that normal-weight children of obese parents may have a lower metabolic rate than normal-weight children of non-obese parents, which can lead to weight problems in adulthood. All of this suggests that a predisposition to obesity can be inherited.
However, the fact that obesity has increased so much in the last few decades appears to discount genetics as the main cause. According to Stephen O'Rahilly, professor of clinical biochemistry and medicine at Cambridge University, the influence of genetics on modern levels of obesity is insignificant:
"Nothing genetic explains the rise in obesity. We can't change our genes over 30 years."
- Source: http://www.annecollins.com/obesity/causes-of-obesity.htm