Key Points
• Obesity is a condition in which abnormal or excessive fat accumulation in adipose tissue impairs health.
• Overweight and obesity are usually measured using body mass index.
• Globally, the prevalence of overweight and obesity is increasing in both adults and in children.
• Increasing levels of overweight and obesity are associated with an increased risk of developing cancer, cardiovascular disease and type 2 diabetes.
• A combination of increased physical activity and suitable weight reducing diets are recommended for overweight/obese adults who wish to lose weight.
OVERWEIGHT AND OBESITY
Obesity is a condition in which abnormal or excessive fat accumulation in adipose tissue impairs health. It is defined in adults as a body mass index (BMI) above 30. Obesity is one of the most visible but, until recently, most neglected public health problems. Body weight is influenced by energy intake (from food) and energy expenditure (needed for basal metabolism such as keeping the heart beating) and for physical activity. If a person regularly consumes more energy (calories) than they use up, they will start to gain weight and eventually become overweight or obese. If a person regularly consumes less energy than they use up they will lose weight. Extra energy is stored in the body as fat. Balancing energy intake and output to maintain a healthy weight has many benefits.
MEASURING BODY MASS INDEX
A useful way to judge whether a person is the appropriate weight for their height is to work out thier BMI. This can be assessed by dividing a person's weight (kg) by height (m)2. The BMI cut offs (listed below) apply to ‘normal’ healthy adults. It is not appropriate for pregnant women, or for use in some medical conditions or with children. They may also be inappropriate for athletes and some ethnic groups (as BMI does not distinguish between fat and fat-free mass). For example, a BMI over 27.5 in an Asian person has been estimated by the World Health Organisation to carry the same health risk as a BMI of 30 in a white Caucasian person. It is more difficult to assess obesity in children, so special charts have been developed which take into account growth, gender and age.
In general, BMIs are classified in four categories and according to level of body weight and as follows:
A BMI of:
Less than 20 – Underweight
Over 20 to 25 – Desirable or healthy range
Over 25-30 – Overweight
Over 30-35 – Obese (Class I)
Over 35-40 – Obese (Class II)
Over 40 – Morbidly or severely obese (Class III)
A strong relationship exists between BMI and risk of associated diseases whereby individuals with a BMI of less than 25 have a low-average risk, and those with a BMI above 40 have a very severe disease risk. For further details see table in attached pdf.
HOW COMMON IS OVERWEIGHT AND OBESITY?
In the early 1980s 6 of men and 8% of women in the UK were obese. The latest (Henderson et al. 2003) figures for Great Britain show that 42% of men and 32% of women are overweight (i.e. have a BMI between 25 and 30), and 25% of men and 20% of women are obese (BMI>30). Obesity tends to be more common among people aged 40-60 years and those from lower income groups. Today, more adults are obese than ever before. The number of obese children is also increasing. According to the Health Survey for England, 5.5% of boys and 7.2% of girls, aged 2-15 years, were obese in 2002. Overall, over 1 in 5 boys (21.8%) and 1 in 4 girls (27.5%) is either overweight or obese using recent international classifications.
Obesity is no longer a disease that only affects the more developed, affluent countries. It is now a worldwide public health problem, affecting all age and socio-economic groups. In 1995 it was estimated that worldwide there were 200 million obese adults and 18 million overweight children under-five. In 2000, more than 300 million adults were estimated to be obese; 132 million in developed countries and 170 million in other countries. Overall the increase in the prevalence of obesity has been most dramatic amongst more affluent populations of less developed countries - those countries said to be in transition.
Key Points
• Obesity is a condition in which abnormal or excessive fat accumulation in adipose tissue impairs health.
• Overweight and obesity are usually measured using body mass index.
• Globally, the prevalence of overweight and obesity is increasing in both adults and in children.
• Increasing levels of overweight and obesity are associated with an increased risk of developing cancer, cardiovascular disease and type 2 diabetes.
• A combination of increased physical activity and suitable weight reducing diets are recommended for overweight/obese adults who wish to lose weight.
OVERWEIGHT AND OBESITY
Obesity is a condition in which abnormal or excessive fat accumulation in adipose tissue impairs health. It is defined in adults as a body mass index (BMI) above 30. Obesity is one of the most visible but, until recently, most neglected public health problems. Body weight is influenced by energy intake (from food) and energy expenditure (needed for basal metabolism such as keeping the heart beating) and for physical activity. If a person regularly consumes more energy (calories) than they use up, they will start to gain weight and eventually become overweight or obese. If a person regularly consumes less energy than they use up they will lose weight. Extra energy is stored in the body as fat. Balancing energy intake and output to maintain a healthy weight has many benefits.
MEASURING BODY MASS INDEX
A useful way to judge whether a person is the appropriate weight for their height is to work out thier BMI. This can be assessed by dividing a person's weight (kg) by height (m)2. The BMI cut offs (listed below) apply to ‘normal’ healthy adults. It is not appropriate for pregnant women, or for use in some medical conditions or with children. They may also be inappropriate for athletes and some ethnic groups (as BMI does not distinguish between fat and fat-free mass). For example, a BMI over 27.5 in an Asian person has been estimated by the World Health Organisation to carry the same health risk as a BMI of 30 in a white Caucasian person. It is more difficult to assess obesity in children, so special charts have been developed which take into account growth, gender and age.
In general, BMIs are classified in four categories and according to level of body weight and as follows:
A BMI of:
Less than 20 – Underweight
Over 20 to 25 – Desirable or healthy range
Over 25-30 – Overweight
Over 30-35 – Obese (Class I)
Over 35-40 – Obese (Class II)
Over 40 – Morbidly or severely obese (Class III)
A strong relationship exists between BMI and risk of associated diseases whereby individuals with a BMI of less than 25 have a low-average risk, and those with a BMI above 40 have a very severe disease risk. For further details see table in attached pdf.
HOW COMMON IS OVERWEIGHT AND OBESITY?
In the early 1980s 6 of men and 8% of women in the UK were obese. The latest (Henderson et al. 2003) figures for Great Britain show that 42% of men and 32% of women are overweight (i.e. have a BMI between 25 and 30), and 25% of men and 20% of women are obese (BMI>30). Obesity tends to be more common among people aged 40-60 years and those from lower income groups. Today, more adults are obese than ever before. The number of obese children is also increasing. According to the Health Survey for England, 5.5% of boys and 7.2% of girls, aged 2-15 years, were obese in 2002. Overall, over 1 in 5 boys (21.8%) and 1 in 4 girls (27.5%) is either overweight or obese using recent international classifications.
Obesity is no longer a disease that only affects the more developed, affluent countries. It is now a worldwide public health problem, affecting all age and socio-economic groups. In 1995 it was estimated that worldwide there were 200 million obese adults and 18 million overweight children under-five. In 2000, more than 300 million adults were estimated to be obese; 132 million in developed countries and 170 million in other countries. Overall the increase in the prevalence of obesity has been most dramatic amongst more affluent populations of less developed countries - those countries said to be in transition.
OVERWEIGHT AND OBESITY AND HEALTH
Severe obesity is associated with a 12 fold increase in mortality in 25-35 year olds when compared to lean individuals. A recent report estimated that in England 30,000 deaths per year are obesity-related. On average, each person whose death could be attributed to obesity lost nine years of life.
Obesity is the most important dietary factor in chronic diseases such as cancer, cardiovascular disease and type 2 diabetes. Obesity is second only to smoking as a cause of cancer. People who are overweight or obese are more likely to suffer from coronary heart disease, type 2 diabetes, gallstones, osteoarthritis (knees), high blood pressure and some types of cancer. Women are more likely to have complications during and after pregnancy . The World Health Organisation has predicted that one of the consequences of the global epidemic of obesity will be 300 million people with type 2 diabetes by 2025.
It is not just a problem of excess fat, but where that fat is deposited. People who have extra weight (fat) around their middle - ‘apple shaped’ - are at more risk of some of these diseases than those who have most of the extra weight around their hips and thighs - ‘pear shaped’. Because the health risks of obesity are compounded by the influence of fat distribution, waist:hip ratios or waist circumferences, are now commonly measured. In general, men are at increased risk of obesity-related diseases when their waist circumference reaches 94cm (37 inches). For women, risks increase at 80cm (32 inches). The risks of disease becomes substantially increased at 102cm (40 inches) for men and 88cm (35 inches) for women.
PLUMP’ BUT NOT OBESE
Being overweight (BMI 25-30), but not obese (BMI greater than 30), also poses increased risks to health, and it is important that people in this category should not put on any more weight and ensure that they are physically active, make sensible dietary choices and do not smoke.
In many countries, there are cultural pressures for people to be slim. Many people try to lose weight even though they are in the normal weight range for their height or only slightly ‘plump’. Unnecessary slimming is not advised, as this may lead to a person becoming underweight, and in severe cases may be a factor in the development of an eating disorder, e.g. anorexia nervosa.
THE ROLE OF PHYSICAL ACTIVITY
Many people in countries such as the UK have very inactive lifestyles - few people have physically active jobs or do significant amounts of exercise in their free time. Many people have a low level of activity because of watching television, playing computer games, and using a car rather than walking for short journeys. Lack of activity is an important factor in the increasing prevalence of obesity. Walking or cycling instead of using a car, going to exercise classes and taking part in team sports such as football or basketball can all help a person maintain a healthy body weight by increasing energy expenditure. People who are very overweight find it more difficult to be physically active and this may add to their health problems. Any form of activity or exercise that is enjoyed should be encouraged. People who are already overweight are usually encouraged to become more active as well as reducing the amount of energy (calories) in foodprovided by their diet. Being physically active is important not just in the prevention of overweight and obesity, but also to prevent other diseases such as cardiovascular disease and type 2 diabetes.
A recent report by the Chief Medical Officer on physical activity emphasises the beneficial relationship between physical activity and health. It recommends:
• that in order to benefit health, individuals should participate in at least 30 minutes of at least moderate intensity activity on five or more days a week
• that the 30 minutes of physical activity does not have to be taken all at once – for example three brisk walks of 10 minutes in duration is equally beneficial.
• that in order to prevent obesity, many individuals will need to participate in between 45 and 60 minutes of moderate intensity physical activity each day.
• that children and young people engage in at least 60 minutes of at least moderate intensity exercise every day.
LOSING WEIGHT
Preventing obesity is important, as ‘dieting’ can be difficult, especially if dietary changes cannot easily be maintained as part of someone’s lifestyle in the long term. Diets often ‘fail’, but this is usually because people revert to their old eating habits and/or levels of activity, rather than making changes for life.
If someone is obese or overweight, they may need advice from their doctor or a dietitian about a suitable weight-reducing diet. They can also join a reputable slimming club. These can be good opportunities for someone to make general improvements to their diet. Special slimming products are not always necessary, but are useful to ‘kick-start’ a diet and prove to someone that they can lose weight. Children who are very overweight or obese must be properly medically supervised to ensure that their growth and development is not compromised. New guidelines on the treatment of childhood obesity have recently been published by the Royal College of Paediatrics and Child Health.
YO-YO DIETING
In an attempt to control or lose weight, some women and men experience a pattern of repeated losses and subsequent regain of body weight. This sort of pattern is also known as weight cycling, and is not confined to people who are overweight.
It is now clear that when we lose weight, there is a fall in our basal metabolic rate (BMR) - the amount of energy (calories) we need to go about our day to day lives. This is because BMR is related to the amount of lean tissue (e.g. muscle) we have. When we lose weight, most of the loss is fat or adipose tissue, but a proportion of the loss is non-fat (lean) tissue. Loss of lean tissue results in a reduction in BMR. The relative amount of lean tissue lost is greater when weight loss is very rapid. Subsequent weight gain will be likely as the amount of dietary energy needed to maintain body weight will have fallen with the loss of lean tissue (hence the term yo-yo dieting). This is why experts recommend a gradual weight loss of about 2lb (1kg) per week on a calorie intake of about 1500 kcal/day for women, combined with an increase in physical activity.
Although being obese is not beneficial to health, some concern has been expressed about the potential negative health consequences of yo-yo dieting.
Yo-yo dieting can cause personal upset because it is disheartening to regain lost weight. It is better to lose weight more slowly and maintain the loss. In some circumstances yo-yo dieting can result in poor body image and a negative attitude towards food.
People who are not overweight should be encouraged to maintain a normal weight rather than a fashionably underweight state. Also, more attention should be paid to helping overweight people maintain their weight loss, rather than falling into a loss-regain-loss cycle.
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How can I lose weight? What is a healthy weight?, What is a healthy shape?
