| No: 05 | May 2007 |
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It is both an individual clinical condition and is increasingly viewed as a serious public health problem. These include cardiovascular diseases, diabetes mellitus type 2, high blood pressure, high blood cholesterol, and triglyceride levels (combined hyperlipidemia). CAUSES Overweight and obesity result from an energy imbalance. This involves eating too many calories and not getting enough physical activity. Body weight is the result of genes, metabolism, behavior, environment, culture, and socioeconomic status. Energy imbalance – The situation when the number of calories consumed is not equal to the number of calories used Weight Gain: Calories Consumed > Calories Used Weight Loss: Calories Consumed < Calories Used No Weight Change: Calories Consumed = Calories Used Calories Used Our bodies need calories for daily functions such as breathing, digestion, and daily activities. Weight gain occurs when calories consumed exceed this need. Physical activity plays a key role in energy balance because it uses up calories consumed. Regular physical activity is good for overall health. Physical activity decreases the risk for colon cancer, diabetes, and high blood pressure. It also helps to control weight, contributes to healthy bones, muscles, and joints Overeating In its simplest conception, obesity is only made possible when the lifetime energy intake exceeds lifetime energy expenditure by more than it does for individuals of "normal weight". When food energy intake exceeds energy expenditure, fat cells (and to a lesser extent muscle and liver cells) throughout the body take in the energy and store it as fat. Environment People may make decisions based on their environment or community. Communities, homes, and workplaces can all influence people's health decisions. Because of this influence, it is important to create environments in these locations that make it easier to engage in physical activity and to eat a healthy diet Genetics Science shows that genetics plays a role in obesity. Genes can directly cause obesity in disorders such as Bardet-Biedl syndrome and Prader-Willi syndrome. In 2007, the Peninsula Medical School and Oxford University published a study showing a link between a mutated FTO gene and obesity. The mutated gene had only one incorrect nucleotide. Those having a single copy of the mutated gene have a 30% increased risk of obesity, while those with two have a 70% increased risk. However genes do not always predict future health. Genes and behavior may both be needed for a person to be overweight. Other Factors Diseases and Drugs Some illnesses may lead to obesity or weight gain. These may include Cushing's disease, and polycystic ovary syndrome. Drugs such as steroids and some antidepressants may also cause weight gain Tendencies of ethnic groups Certain populations and individuals may be more prone to obesity than others, and the ability to take advantage of rare periods of abundance and use such abundance by storing energy efficiently was undoubtedly an evolutionary advantage in times when food was scarce. Individuals with greater adipose reserves were more likely to survive famine. This tendency to store fat is likely maladaptive in a society with adequate and stable food supplies.
DEFINITION OF OBESITY FOR ADULTS For adults, overweight and obesity ranges are determined by using weight and height to calculate a number called the “body mass index” (BMI). BMI was developed by the Belgian statistician and anthropometrist Adolphe Quetelet. It is calculated as follws: BMI = subject's weight (kg) / height m2) or BMI = subject's weight (lbs.) * 703 / height(inches)2 According to the calculated BMI, people are categorized on their weight. The current definitions commonly in use establish the following values, agreed in 1997 and published in 2000:
It is important to remember that although BMI correlates with the amount of body fat, BMI does not directly measure body fat. As a result, some people, such as athletes, may have a BMI that identifies them as overweight even though they do not have excess body fat. Other methods of estimating body fat and body fat distribution include measurements of skinfold thickness and waist circumference, calculation of waist-to-hip circumference ratios, and techniques such as ultrasound, computed tomography, and magnetic resonance imaging (MRI). Body fat measurement An alternative way to determine obesity is to assess percent body fat. Doctors and scientists generally agree that men with more than 25% body fat and women with more than 30% body fat are obese. However, it is difficult to measure body fat precisely. The most accepted method has been to weigh a person underwater, but underwater weighing is a procedure limited to laboratories with special equipment. Circumference and waist-hip ratio measurement The limits for waist circumference and waist-hip ratio are as follows:
Definitions for Children and Teens For children and teens, BMI ranges above a normal weight have different labels (at risk of overweight and overweight). Additionally, BMI ranges for children and teens are defined so that they take into account normal differences in body fat between boys and girls and differences in body fat at various ages. For more information about BMI for children and teens (also called BMI-for-age), click here. http://www.cdc.gov/nccdphp/dnpa/bmi/childrens_BMI/about_childrens_BMI.htm THERAPY A more intractable therapeutic problem appears to be weight loss maintenance. Of dieters who manage to lose 10% or more of their body mass in studies, 80-95% will regain that weight within two to five years. It appears that the homeostatic mechanisms regulating body weight are very robust (see leptin, for example), and vigorously defend against weight loss. Click here to learn about leptin. http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=164160 Behavior and environment play a large role causing people to be overweight and obese. These are the greatest areas for prevention and treatment actions. It is possible to treat obesity with a balanced dietary program based on energy needs of the body and regular exercise. References http://www.cdc.gov/nccdphp/dnpa/obesity/contributing_factors.htm http://www.cdc.gov/nccdphp/dnpa/obesity/defining.htm http://en.wikipedia.org/wiki/Obesity |
Obesity, especially central obesity (male-type or waist-predominant obesity), is an important risk factor for the "metabolic syndrome" ("syndrome X"), the clustering of a number of diseases.
