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Why Lose Weight?
Since the mid-seventies, the prevalence of overweight and obesity has increased sharply for both adults and children. Recent data from two international surveys show that among adults aged 20–74 years the prevalence of obesity increased from 15.0% (in the 1976–1980 survey) to 32.9% (in the 2003–2004 survey) in the developed world.
The two surveys also show increases in overweight among children and teens. For children aged 2–5 years, the prevalence of overweight increased from 5.0% to 13.9%; for those aged 6–11 years, prevalence increased from 6.5% to 18.8%; and for those aged 12–19 years, prevalence increased from 5.0% to 17.4%.
These increasing rates raise concern because of their implications for health. Being overweight or obese increases the risk of many diseases and health conditions, including the following:
Hypertension (high blood pressure)
Osteoarthritis (a degeneration of cartilage and its underlying bone within a joint)
Dyslipidemia (for example, high total cholesterol or high levels of triglycerides)
Type 2 diabetes
Coronary heart disease
Stroke
Gallbladder disease
Sleep apnea and respiratory problems
Some cancers (endometrial, breast, and colon)
In the US for example one of the national health objectives for the year 2010 is to reduce the prevalence of obesity among adults to less than 15%, current data indicates that the situation is worsening rather than improving.
Defining Overweight and Obesity
Overweight and obesity are both labels for ranges of weight that are greater than what is generally considered healthy for a given height. The terms also identify ranges of weight that have been shown to increase the likelihood of certain diseases and other health problems.
Definitions 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 is used because, for most people, it correlates with their amount of body fat.
An adult who has a BMI between 25 and 29.9 is considered overweight.
An adult who has a BMI of 30 or higher is considered obese.
See the following table for an example.
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. For more information about BMI, visit Body Mass Index.
Other methods of estimating body fat and body fat distribution include measurements of skin fold thickness and waist circumference, calculation of waist-to-hip circumference ratios, and techniques such as ultrasound, computed tomography, and magnetic resonance imaging (MRI).
Assessing Health Risks Associated with Overweight and Obesity
BMI is just one indicator of potential health risks associated with being overweight or obese. For assessing someone’s likelihood of developing overweight or obesity related diseases, the following predictors should be considered:
The individual’s waist circumference (because abdominal fat is a predictor of risk for obesity-related diseases).
Other risk factors the individual has for diseases and conditions associated with obesity (for example, high blood pressure or physical inactivity).
Contributing Factors
Overweight and Obesity: An Overview
Is there a quick answer to the question, "what contributes to overweight and obesity?"
Overall there are a variety of factors that play a role in obesity. This makes it a complex health issue to address. This section will address how behavior, environment, and genetic factors may have an effect in causing people to be overweight and obese.
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, behaviour, environment, culture, and socioeconomic status.
Behaviour and environment play a large role causing people to be overweight and obese. These are the greatest areas for prevention and treatment actions.
Overweight and obesity are a result of energy imbalance over a long period of time. The cause of energy imbalance for each individual may be due to a combination of several factors. Individual behaviors, environmental factors, and genetics all contribute to the complexity of the obesity epidemic.
| Height |
Weight |
BMI |
Considered |
| 5'9" |
124 lbs or less |
Below 18.5 |
Underweight |
| |
125 lbs to 168 lbs |
18.5 to 24.9 |
Healthy weight |
| |
169 lbs to 202 lbs |
25.0 to 29.9 |
Overweight |
| |
203 lbs or more |
30 or higher |
Obese |
Energy imbalance - When the number of calories consumed is not equal to the number of calories used.
Energy Balance is like a scale. Weight gain occurs when calories consumed are greater than calories used.
Weight Gain:
Calories Consumed > Calories Used
Weight Loss:
Calories Consumed < Calories Used
No Weight Change:
Calories Consumed = Calories Used
Genetics and the environment may increase the risk of personal weight gain. However, the choices a person makes in eating and physical activity also contributes to overweight and obesity. Behavior can increase a person’s risk for gaining weight.
Looking back at the energy balance scale, weight gain is a result of extra calorie consumption, decreased calories used (reduced physical activity) or both. Personal choices concerning calorie consumption and physical activity can lead to energy imbalance.
Calorie Consumption
In Western countries a changing environment has broadened food options and eating habits. Grocery stores stock their shelves with a greater selection of products. Pre-packaged foods, fast food restaurants, and soft drinks are also more accessible. While such foods are fast and convenient they also tend to be high in fat, sugar, and calories. Choosing many foods from these areas may contribute to an excessive calorie intake. Some foods are marketed as healthy, low fat, or fat-free, but may contain more calories than the fat containing food they are designed to replace. It is important to read food labels for nutritional information and to eat in moderation.
Portion sizes have also increased. People may be eating more during a meal or snack because of larger portion sizes. This results in increased calorie consumption. If the body does not burn off the extra calories consumed from larger portions, fast food, or soft drinks, weight gain can occur. Choosing a variety of healthy foods in the correct portion sizes is helpful for achieving and maintaining a healthy weight.
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.
Physical activity is any bodily movement produced by skeletal muscles that results in an expenditure of energy with a range of activities such as
Occupational work
Carpentry, construction work, waiting tables, farming
Household chores
Washing floors or windows, gardening or yard work
Leisure time activities
Walking, skating, biking, swimming, playing Frisbee, dancing Structured sports or exercise Softball, tennis, football, aerobics
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; reduces falls among the elderly; and helps to relieve the pain of arthritis. Physical activity does not have to be strenuous to be beneficial. Moderate physical activity, such as 30 minutes of brisk walking five or more times a week, also has health benefits.
Despite all the benefits of being physically active, most people in Western countries are sedentary. Technology has created many time and labor saving products. Some examples include cars, elevators, computers, dishwashers, and televisions. Cars are used to run short distance errands instead of people walking or riding a bicycle. As a result, these recent lifestyle changes have reduced the overall amount of energy expended in our daily lives.
The belief that physical activity is limited to exercise or sports, may keep people from being active. Another myth is that physical activity must be vigorous to achieve health benefits. Physical activity is any bodily movement that results in an expenditure of energy. Moderate-intensity activities such as household chores, gardening, and walking can also provide health benefits. Confidence in one’s ability to be active will help people make choices to adopt a physically active lifestyle.
Environment
People may make decisions based on their environment or community. For example, a person may choose not to walk to the store or to work because of a lack of sidewalks. 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. The following table provides some examples of these steps.
Steps to Help Prevent and Decrease Overweight and Obesity
Home
Reduce time spent watching television and in other sedentary behaviours
Build physical activity into regular routines
Schools
Ensure that the school breakfast and lunch programs meet nutrition standards
Provide food options that are low in fat, calories, and added sugars
Provide all children, from prekindergarten through grade 12, with quality daily physical education
Work
Create more opportunities for physical activity at work sites
Community
Promote healthier choices including at least 5 servings of fruits and vegetables a day, and reasonable portion sizes
Encourage the food industry to provide reasonable food and beverage portion sizes
Encourage food outlets to increase the availability of low-calorie, nutritious food items
Create opportunities for physical activity in communities
Genetics
How do genes affect obesity?
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.
However genes do not always predict future health. Genes and behavior may both be needed for a person to be overweight. In some cases multiple genes may increase one’s susceptibility for obesity and require outside factors; such as abundant food supply or little physical activity.
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.
A doctor is the best source to tell you whether illnesses, medications, or psychological factors are contributing to weight gain or making weight loss hard.
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