Fundamentals of Human Nutrition/Overweight and obesity

Overweight and Obesity

'What Is Obesity?'

Obesity is an excess proportion of total body fat. A person is considered obese when his or her weight is 20% or more above normal weight. The most common measure of obesity is the body mass index or BMI. A person is considered overweight if his or her BMI is between 25 and 29.9; a person is considered obese if his or her BMI is over 30.

"Morbid obesity" means that a person is either 50%-100% over normal weight, more than 100 pounds over normal weight, has a BMI of 40 or higher, or is sufficiently overweight to severely interfere with health or normal function.

Measuring obesity

The most common method of measuring obesity is calculating an individual’s Body Mass Index (BMI). This is calculated by dividing a person’s weight measurement (in kilograms) by the square of their height (in metres).

In adults, a BMI of 25 to 29.9 means that person is considered to be overweight, and a BMI of 30 or above means that person is considered to be obese.

In children and adolescents, BMI varies with age and sex, so the BMI score for children and adolescents is related to the UK 1990 BMI growth reference charts in order to determine a child’s weight status.

BMI is the best way we have to measure the prevalence of obesity at the population level. No specialised equipment is needed and therefore it is easy to measure accurately and consistently across large populations. BMI is also widely used around the world, which enables comparisons between countries, regions and population sub-groups.

For most people, their BMI correlates well with their level of body fat. However, certain factors such as fitness and ethnic origin can sometimes alter the relationship between BMI and body fatness. So then other measurements such as waist circumference and skin fold thickness can also be collected to confirm an individual person’s weight status.

When to Seek Help for Obesity

You should call your doctor if you are having emotional or psychological issues related to your obesity, need help losing weight, or if you fall into either of the following categories.

If your BMI is 30 or greater, you're considered obese. You should talk to your doctor about losing weight since you are at high risk of having health problems. If you have an "apple shape"—a so-called, "potbelly" or "spare tire"—you carry more fat in and around your abdominal organs. Fat deposited primarily around your middle increases your risk of many of the serious conditions associated with obesity. Women's waist measurement should fall below 35 inches. Men's should be less than 40 inches. If you have a large waist circumference, talk to your doctor about how you can lose weight.

10.3.2.1 Global statistics

The prevalence of obesity in England has more than tripled in the last 25 years. The latest Health Survey for England (HSE) data shows that in England in 2010:

62.8% of adults (aged 16 or over) were overweight or obese
30.3% of children (aged 2–15) were overweight or obese
26.1% of all adults and 16% of all children were obese

Foresight’s Tackling Obesities: Future Choices report, published in October 2007, predicted that if no action was taken, 60% of men, 50% of women and 25% of children in Britain would be obese by 2050. Recently reported modelling suggests that without action 41-48% of men and 35-43% of women could be obese by 2030.

10.3.2.2 Causes

Obesity occurs when a person consumes more calories than he or she burns. For many people this boils down to eating too much and exercising too little. But there are other factors that also play a role in obesity. These may include:

Age. As you get older, your body's ability to metabolize food slows down and you do not require as many calories to maintain your weight. This is why people note that they eat the same and do the same activities as they did when they were 20 years old, but at age 40, gain weight.

Gender. Women tend to be more overweight than men. Men have a higher resting metabolic rate (meaning they burn more energy at rest) than women, so men require more calories to maintain their body weight. Additionally, when women become postmenopausal, their metabolic rate decreases. That is partly why many women gain weight after menopause.

Genetics. Obesity (and thinness) tends to run in families. In a study of adults who were adopted as children, researchers found that participating adult weights were closer to their biological parents' weights than their adoptive parents'. The environment provided by the adoptive family apparently had less influence on the development of obesity than the person's genetic makeup. In fact, if your biological mother is heavy as an adult, there is approximately a 75% chance that you will be heavy. If your biological mother is thin, there is also a 75% chance that you will be thin. Nevertheless, people who feel that their genes have doomed them to a lifetime of obesity should take heart. Many people genetically predisposed to obesity do not become obese or are able to lose weight and keep it off.

Environmental factors. Although genes are an important factor in many cases of obesity, a person's environment also plays a significant role. Environmental factors include lifestyle behaviors such as what a person eats and how active he or she is.

Physical activity. Active individuals require more calories than less active ones to maintain their weight. Additionally, physical activity tends to decrease appetite in obese individuals while increasing the body's ability to preferentially metabolize fat as an energy source. Much of the increase in obesity in the last 20 years is thought to have resulted from the decreased level of daily physical activity.

Psychological factors. Psychological factors also influence eating habits and obesity. Many people eat in response to negative emotions such as boredom, sadness, or anger. People who have difficulty with weight management may be facing more emotional and psychological issues; about 30% of people who seek treatment for serious weight problems have difficulties with binge eating. During a binge-eating episode, people eat large amounts of food while feeling they can't control how much they are eating.

Illness. Although not as common as many believe, there are some illnesses that can cause obesity. These include hormone problems such as hypothyroidism (poorly acting thyroid slows metabolism), depression, and some rare diseases of the brain that can lead to overeating.

Medication. Certain drugs, such as steroids and some antidepressants, may cause excessive weight gain.

10.3.2.3 Health risks

Being obese or overweight brings significant risks at a range of different points throughout life. The health risks for adults are stark. We know that, compared with a healthy weight man, an obese man is:

five times more likely to develop type 2 diabetes
three times more likely to develop cancer of the colon
more than two and a half times more likely to develop high blood pressure – a major risk factor for stroke and heart disease

An obese woman, compared with a healthy weight woman, is:

almost 13 times more likely to develop type 2 diabetes
more than four times more likely to develop high blood pressure
more than three times more likely to have a heart attack

Obesity and overweight pose a major risk for serious diet-related chronic diseases, including type 2 diabetes, cardiovascular disease, hypertension and stroke, and certain forms of cancer. The health consequences range from increased risk of premature death, to serious chronic conditions that reduce the overall quality of life.

For the USA:

of 22 industrialized countries, the U.S. has the highest obesity statistics
2/3 of Americans over age 20 are overweight
nearly 1/3 of Americans over age 20 are obese

Overweight and obesity lead to adverse metabolic effects on blood pressure, cholesterol, triglycerides and insulin resistance.

The likelihood of developing Type 2 diabetes and hypertension rises steeply with increasing body fatness. Confined to older adults for most of the 20th century, this disease now affects obese children even before puberty. Approximately 85% of people with diabetes are type 2, and of these, 90% are obese or overweight.

Raised BMI also increases the risks of cancer of the breast, colon, prostate, endometroium, kidney and gallbladder.

Chronic overweight and obesity contribute significantly to osteoarthritis, a major cause of disability in adults. Although obesity should be considered a disease in its own right, it is also one of the key risk factors for other chronic diseases together with smoking, high blood pressure and high blood cholesterol.

According to the American Cancer Society, obesity cost an estimated $75 billion in 2003 because of the long and expensive treatment for several of its complications. According to the National Institute of Health, $75-$125 billion is spent on indirect and direct costs due to obesity-related diseases.

Childhood overweight and obesity

Introduction

Children need a healthy, balanced diet that gives them enough energy to grow and develop. This means that children usually need to take in more energy than they use and this extra energy forms new tissues as they grow. However, if children regularly take in too much energy, this is stored as fat and they will put on excess weight. 1

Childhood obesity is one of the most serious public health challenges of the 21st century. The problem is global and is steadily affecting many low- and middle-income countries, particularly in urban settings. The prevalence has increased at an alarming rate. Globally, in 2010 the number of overweight children under the age of five, is estimated to be over 42 million. Close to 35 million of these are living in developing countries.2

Many factors, including genetics, environment, metabolism, lifestyle, and eating habits, are believed to play a role in the development of obesity. However, more than 90% of cases are idiopathic; less than 10% are associated with hormonal or genetic causes.3

Overweight and Obesity

Overweight and obesity are defined as abnormal or excessive fat accumulation that presents a risk to health.2 Operational definitions of obesity in adults are derived from statistical data that analyze the association between body mass and the risk of acute and long-term morbidity and mortality. Because acute medical complications of obesity are less common in children and adolescents than in adults, and because longitudinal data on the relation between childhood weight and adult morbidity and mortality are more difficult to interpret, no single definition of obesity in childhood and adolescence has gained universal approval.

Some investigators have used the terms overweight, obese, and morbidly obese to refer to children and adolescents whose weights exceed those expected for heights by 20%, 50%, and 80-100%, respectively. The body mass index (BMI) has not been consistently used or validated in children younger than 2 years. Because weight varies in a continuous rather than a stepwise fashion, the use of these arbitrary criteria is problematic and may be misleading. 3

A few extra pounds does not suggest obesity. However they may indicate a tendency to gain weight easily and a need for changes in diet and/or exercise. Generally, a child is not considered obese until the weight is at least 10 percent higher than what is recommended for their height and body type. Obesity most commonly begins between the ages of 5 and 6, or during adolescence. Studies have shown that a child who is obese between the ages of 10 and 13 has an 80 percent chance of becoming an obese adult. 4

Measuring overweight and obesity

It is difficult to develop one simple index for the measurement of overweight and obesity in children and adolescents because their bodies undergo a number of physiological changes as they grow. Depending on the age, different methods to measure a body's healthy weight are available.2

Using Body Mass Index (BMI) to Estimate Overweight and Obesity

The BMI is the tool most commonly used to estimate overweight and obesity in children and adults. The BMI is a continuous, although imperfect, measure of body fatness. Calculated as weight (kg) divided by height (m2).The BMI is used because, for most people, it correlates with the amount of fat in their bodies. Children grow at different rates at different times, so it is not always easy to tell if a child is overweight. The BMI correlates closely with total body fat (TBF), which is estimated using dual-energy x-ray absorptiometry (DEXA) scanning in children who are overweight and obese. Normal values for BMI vary with age, sex, and pubertal status, and standard curves representing the 5th through the 95th percentiles for BMI in childhood and adolescence were generated using data from the 1988-1994 NHANES. 3 5

BMI	Classification
At or above the 85th percentile	Overweight or obese
Overweight or obese	Obese

Special charts, called BMI centile charts, have been developed to show whether children are under or overweight for their age. These charts compare a child’s BMI against other children of the same sex and age.

Tool E4 -This tool contains detailed information on the measurement and assessment of overweight and obesity in children. It provides information on how to measure overweight and obesity using Body Mass Index (BMI) and growth reference charts; provides information on measuring waist circumference; and provides details on how to assess overweight and obesity in children. BMI charts are provided at the end of this tool for girls and boys. This tool is consistent with NICE guidance and also Department of Health recommendations. It is for all healthcare professionals measuring and assessing overweight and obese children.6

Causes for Obesity

The causes of obesity are complex and include genetic, biological, behavioral and cultural factors. Obesity occurs when a person eats more calories than the body burns up. If one parent is obese, there is a 50 percent chance that their children will also be obese. However, when both parents are obese, their children have an 80 percent chance of being obese. Although certain medical disorders can cause obesity, less than 1 percent of all obesity is caused by physical problems. Obesity in childhood and adolescence can be related to:

poor eating habits
overeating
lack of exercise (i.e., couch potato kids)
family history of obesity
medical illnesses (endocrine, neurological problems)
medications (steroids, some psychiatric medications)
stressful life events or changes (separations, divorce, moves, deaths and abuse)
family and peer problems
low self-esteem
depression or other emotional problems 4

WHO recognizes that the increasing prevalence of childhood obesity results from changes in society. Childhood obesity is mainly associated with unhealthy eating and low levels of physical activity, but the problem is linked not only to children's behaviour but also, increasingly, to social and economic development and policies in the areas of agriculture, transport, urban planning, the environment, food processing, distribution and marketing, as well as education.

The problem is societal and therefore it demands a population-based multisectoral, multi-disciplinary, and culturally relevant approach.

Unlike most adults, children and adolescents cannot choose the environment in which they live or the food they eat. They also have a limited ability to understand the long-term consequences of their behaviour. They therefore require special attention when fighting the obesity epidemic. 2

Consequences of childhood obesity

Health risks now

Childhood obesity can have a harmful effect on the body in a variety of ways. Obese children are more likely to have–

High blood pressure and high cholesterol, which are risk factors for cardiovascular disease (CVD). In one study, 70% of obese children had at least one CVD risk factor, and 39% had two or more.
Increased risk of impaired glucose tolerance, insulin resistance and type 2 diabetes.
Breathing problems, such as sleep apnea, and asthma.
Joint problems and musculoskeletal discomfort.
Fatty liver disease, gallstones, and gastro-esophageal reflux (i.e., heartburn).
Obese children and adolescents have a greater risk of social and psychological problems, such as discrimination and poor self-esteem, which can continue into adulthood.

Health risks later

Obese children are more likely to become obese adults. Adult obesity is associated with a number of serious health conditions including heart disease, diabetes, and some cancers.
If children are overweight, obesity in adulthood is likely to be more severe. 7

Prevention of obesity in children

Overweight and obesity, as well as related noncommunicable diseases, are largely preventable. It is recognized that prevention is the most feasible option for curbing the childhood obesity epidemic since current treatment practices are largely aimed at bringing the problem under control rather than effecting a cure. The goal in fighting the childhood obesity epidemic is to achieve an energy balance which can be maintained throughout the individual's life-span.

General recommendations

increase consumption of fruit and vegetables, as well as legumes, whole grains and nuts;
limit energy intake from total fats and shift fat consumption away from saturated fats to unsaturated fats;
limit the intake of sugars; and
be physically active - accumulate at least 60 minutes of regular, moderate- to vigorous-intensity activity each day that is developmentally appropriate.

Societal Recommendations

Curbing the childhood obesity epidemic requires sustained political commitment and the collaboration of many public and private stakeholders.

Governments, International Partners, Civil Society, NGO's and the Private Sector have vital roles to play in shaping healthy environments and making healthier diet options for children and adolescents affordable, and easily accessible. It is therefore WHO's objective to mobilize these partners and engage them in implementing the Global Strategy on Diet, Physical Activity and Health.

WHO supports the designation, the implementation, the monitoring and the leadership of actions. A multisectoral approach is essential for sustained progress: it mobilizes the combined energy, resources and expertise of all global stakeholders involved. 2

Population-based approaches to childhood obesity prevention - The document published by WHO, aims to provide Member States with an overview of the types of childhood obesity prevention interventions that can be undertaken at national, sub-national and local levels. The document first outlines guiding principles for the development of a population-based childhood obesity prevention strategy and then describes the approaches for population-based obesity prevention. There is a broad range of population-level actions that governments can take to prevent childhood obesity. A comprehensive childhood obesity prevention strategy will incorporate aspects of each of the key components. 8

References