1. Obesity and the global burden of disease
2. Prevalence, trends and economics
3. Targets for action
4. The action agenda
5. Potential solutions
6. Tracking outcomes
7. Glossary of terms
8. Key references and further reading
9. Case studies: Available on Nature website at www.naturesj.com/ijo/index.html
International experts participating in the first ever World Health Organization (WHO) Expert Consultation on Obesity in June 1997 immediately recognized that ‘Overweight and obesity represent a rapidly growing threat to the health of populations and an increasing number of countries worldwide.’1
The diverse countries represented at the consultation were: Australia, Bahrain, Canada, Chile, China, Cyprus, Denmark, Egypt, India, Ireland, Japan, Malaysia, Mauritius, Netherlands, Nigeria, Pakistan, Polynesia, South Africa, Sweden, Switzerland, Thailand, UK, USA.
Experts from the United Nations, Food and Agricultural Organization, and WHO Collaborating Centers as well as advisers from the International Obesity Task Force (IOTF) facilitated the recognition of obesity as a global problem.
Development and implementation of effective obesity prevention strategies was identified as an immediate action priority.
This case statement proposes a relevant action agenda—it highlights the need for:
Correcting the societal causes of obesity through direct and indirect actions to change population food intake and physical activity patterns. This requires that a wide range of sectors and settings to be addressed including transport, environment, workplaces, schools, public education, health, food, nutrition, social welfare, and trade and industry
Intervention and commitment to action at all levels, from the individual through the community to national and international players
Links between independent policies and processes in different settings and sectors
Strategies for the population as a whole as well as strategies aimed at improving individual lifestyles
1. Obesity and the global burden of disease
Obesity is a major contributor to the global burden of disease and disability
Overweight and obesity are important risk factors for a wide range of medical conditions, including:
Many life-threatening chronic non-communicable diseases which lead to disability and death, eg heart disease, type 2 diabetes, hypertension, stroke and certain cancers. The risk of developing these conditions is greatest when the majority of excess fat is located around the abdomen (central obesity) rather than around the hips and thighs (peripheral obesity)
A wide range of debilitating conditions which can drastically reduce quality of life and are costly in terms of absence from work and use of health resources, eg osteoarthritis, gallbladder disease, respiratory difficulties, infertility and skin problems
Psychosocial problems, eg clinical depression, lowered self-esteem, job discrimination and other forms of social stigmatization
Non-communicable diseases threaten to overwhelm health care services worldwide
The Global Burden of Disease Study, a collaborative effort of the WHO and The World Bank, provided the first comprehensive picture of the world's present and future health needs.
Globally, in terms of deaths:
Communicable maternal, perinatal and nutritional disorders (the traditional enemies) are expected to account for 10.3 million deaths a year in 2020—a decline from 17.2 million deaths in 1990
Over the same period, deaths from non-communicable diseases are expected to rise from 28.1 million to 49.7 million a year—an increase in absolute numbers of 77%
In terms of disease burden (measured in ‘Disability Adjusted Life Years’, DALYs):
The contribution from communicable maternal, perinatal and nutritional disorders is projected to decline from 44% in 1990 to 20% in 2020
The contribution from non-communicable diseases is expected to rise from 41% in 1990 to 60% in 2020. Ischaemic heart disease is predicted to become the leading worldwide cause of disease burden in 2020 (Table 1)
The non-communicable disease burden outlook in developing countries is particularly serious (see Figure 1)
The largest increases in deaths and disease burden from non-communicable diseases will occur in the developing regions where four-fifths of the world's population live
In the developing world, deaths from non-communicable diseases are expected to rise from 47% of the burden in 1990 to almost 70% in 2020
More people already die from non-communicable diseases than from communicable causes in several major developing regions, eg Latin America and the Caribbean have almost twice as many deaths, and China has four and a half times as many deaths from non-communicable diseases
In countries undergoing economic transition, overnutrition often coexists with undernutrition. People below a body mass index (BMI) of 18.5 kg/m2 tend to be undernourished. However, the distribution of BMI is shifting upwards in many populations. This leads to an increasing proportion of people who are obese (ie above BMI 30 kg/m2; Figure 2)
Recent studies have shown that people who were undernourished in early life and then become obese in adulthood tend to develop conditions such as hypertension, heart disease and diabetes at an earlier age, and in a more severe form, than people who were never undernourished
India and China, with around two billion people in total, still have a large proportion of infants born undernourished. Both are already experiencing high levels of adult obesity and associated chronic disease in many areas
Thus, obesity must be addressed even where undernutrition persists
Type 2 diabetes is one of the major links between obesity and other non-communicable diseases
The World Health Organization estimated that around 143 million adults were diabetic worldwide in 1997. This figure is expected to rise to 154 million by the year 2000 and to 300 million by 2025
The likelihood of developing type 2 diabetes rises steeply with increasing body fatness. Approximately 85% of people with diabetes can be classified as type 2, and of these 90% are obese or overweight
People with type 2 diabetes are at high risk of a range of disabling conditions (eg heart disease, hypertension, amputation, stroke, renal failure and blindness) and premature death
Duration of obesity, accumulation of abdominal body fat, and inactivity further increase the risk of diabetes
Diabetes is now most frequent in developing countries. In countries such as the US, UK and Australia, ethnic minority populations are most at risk, eg American Indians, Micronesians, Polynesians, Asian Indians, Australian Aborigines, Mexican Americans, African Americans and Hispanics
India, China and the US are the three countries with the highest number of adults with diabetes (Table 2)
In 1995, the Established Market Economies had the highest number of persons with diabetes. If current trends continue, India and the Middle Eastern Crescent will have taken over by 2025. Large increases will also be observed in China, Latin America and the Caribbean, and the rest of Asia (Figure 3)
2. Prevalence, trends and economics
Obesity has already reached epidemic proportions in many countries and population groups
A clear relationship exists between average BMI and the prevalence of obesity in a population. When the average is below 23 kg/m2, few individuals are obese. However, for every single unit increase in average BMI above 23 kg/m2, there is an almost 5% increase in obesity prevalence (Figure 4)
Obesity rates in adults are increasing rapidly in all parts of the world, both in affluent Western countries and in poorer nations (see Figure 5)
Current obesity levels range from below 5% in China, Japan and certain African nations to over 75% in urban Samoa (Table 3)
Even in relatively low prevalence countries such as China, levels are almost 20% in some cities
In most populations, more women than men are obese
Childhood obesity is already epidemic in some areas, and on the rise in others
Approximately 22 million children under 5 y are overweight across the world
In Thailand, the prevalence of obesity in 6–12-y-old children rose from 12.2 to 15.6% in just 2 y
In Japan, the percentage of obese children aged 6–14 y resident in Izumiohtsu city doubled from 5 to 10% between 1974 and 1993
In the US, the percentage of obese children aged 6–11 y has more than doubled since the 1960s. Prevalence rose from 5% in 1963–1965 to 11% in 1988–1991 in both sexes. Obesity prevalence in youths aged 12–17 y has also increased dramatically—from 5 to 13% in boys, and from 5 to 9% in girls, between 1966–1970 and 1988–1991 respectively
Obesity can affect all income levels
Economic growth fosters obesity, particularly in developing and transition countries.
As the socioeconomic conditions of a country improve, the average weight of the population rises and the number of people who are obese increases
In the early stages of transition, undernutrition remains the main problem in the poor whilst the more affluent tend to show an increase in people with a high BMI. As transition proceeds, overweight and obesity also begin to increase among the poor, especially among women (Figure 6)
In affluent societies, obesity levels tend to be highest in the lower socio-economic classes—again, especially among women. However, obesity sometimes persists among affluent women in ethnic minority populations. Risks for men may increase when jobs no longer require manual labour
Obesity is an extremely costly health problem
Obesity accounts for 2–6% of total health care costs in several developed countries (Table 4). The true costs are undoubtedly much greater as not all obesity-related conditions are included in the calculations
New methods for measuring the economic costs of obesity are currently being developed. These will include indirect and personal costs to give a more complete picture of the total economic burden that obesity can impose on a country
In the US in 1995, the direct healthcare costs of obesity were similar to those for type 2 diabetes, 1.25 times greater than those of heart disease and 2.7 times greater than those of hypertension (Figure 7)
3. Targets for action
Environmental factors predominate
Development of effective preventive solutions requires a sound understanding of the key forces that are driving the obesity epidemic.
Genes are important in determining a person's susceptibility to weight gain, but societal changes are driving the epidemic; the rapid rises in obesity rates around the world have occurred in too short a time for there to have been any evolutionary genetic changes within populations
Economic growth, modernization, urbanization and globalization of food markets are just some of the societal and environmental forces thought to underlie the epidemic. All are important features of societal development, but they have also led to widespread increases in consumption of high-fat high-energy diets and/or decreases in physical activity
The human body is designed to store fat for times of shortage, an adaptation which has become a liability in modern times. This is true for all populations, albeit to varying degrees, suggesting that obesity rates will continue to increase in the next millennium if current diet and physical activity patterns do not improve
Populations worldwide are consuming diets high in fat and energy
As incomes rise and populations become more urban, diets high in complex carbohydrate and fibre generally give way to more varied diets with a higher proportion of fats, saturated fats and sugars. The greater availability of cheap vegetable oils and fats in the global economy is now resulting in higher fat consumption even among low-income nations
Some developed countries have shown a small decrease in both overall energy intake and the proportion of fat in the diet in recent years. However, many experts believe that this is a distortion caused by dietary under-reporting among other things. Indeed, dietary intakes in most developed countries are still characterized by a high level of fat that is well above the World Health Organization recommended limit of 30% energy
Lifestyles are becoming more and more sedentary
Large shifts towards less physically demanding work have been observed on a worldwide basis, both in terms of the proportion of people working in agriculture, industry and services, and in the type of work within most occupations
Shifts towards less physical activity are also found in the increased use of automated transport, technology in the home, and passive leisure. Proxy indicators of physical inactivity such as television viewing and car ownership parallel changes in obesity rates over recent years (Figure 8)
Few people engage in enough exercise during leisure time to compensate for the decreases in daily energy expenditure associated with sedentary activity in other aspects of their daily routine
Societal solutions are critical, especially for the long term
Societal-level interventions are the key to tackling the obesity problem in a population. Although they may take a long-time to put into place, and even longer to yield results, they can begin to counteract the powerful forces that lead to steady population weight gain.
The vast array of factors impinging upon food intake and energy expenditure in Figure 9, and the numerous interactions between them, challenge the notion of individual ‘free will’ regarding food choice and energy expenditure. Indeed, many things that individuals do are influenced by factors ‘upstream.’
Societal policies and processes operating within and across a range of different settings and sectors influence individual diet and activity patterns, and hence population weight status
Interventions aimed at improving individual lifestyles, when conducted in isolation of societal intervention, tend to have limited success. They are most effective in motivating the socially advantaged who already have sufficient lifestyle options open to them. Over time, this may actually aggravate disparities between the more and less advantaged
No single aspect of the web of policies and processes can be addressed without a potential impact on other areas—many of which have competing commercial interests
Key issues for societal level solutions
Food and nutrition policy initiatives must be central to societal solutions for obesity prevention, but will not suffice on their own
Physical activity policy initiatives are also essential and may be motivated by fields other than health, eg sustainable transport, family recreation
Links are needed between policies and processes in different sectors and social structural levels
The types of initiatives needed to shift policies and process towards the promotion of healthy population diets, activity levels and weight status will differ culturally and between and within countries
Societal approaches must also emphasize increasing options and removing barriers to healthy living among those who are the least advantaged.
Short-term action aimed at improving individual lifestyles should be taken in parallel with efforts to establish long-term remedies from broader public health and policy perspectives.
4. The action agenda
The action agenda for obesity prevention consists of key Recommendations, Principles and Target Outcomes.
From the previous section, it is clear that a comprehensive approach to obesity prevention should:
address both dietary habits and physical activity patterns of the population
address both societal and individual level factors
address both immediate and distant causes
have multiple focal points and levels of intervention (ie at national, regional, community and individual levels)
include both policies and programmes
build links between sectors that may be otherwise viewed as independent
Ground breaking work in the field of obesity prevention has only just begun. The 10 action principles listed in the next column therefore draw on evidence and recommendations from alternative sources including:
community prevention trials conducted for risk reduction of other non-communicable diseases, eg cardiovascular disease, cancer, diabetes; many of these have included interventions to promote healthy eating and physical activity
the principles of health promotion as outlined by the ‘Ottawa Charter for Health Promotion’ and subsequent declarations related to the World Health Organization global strategy ‘Health for All’
Here are the 10 principles upon which efforts to prevent obesity at the population level should be based:
Education alone is not sufficient to change weight-related behaviours. Environmental and societal intervention is also required to promote and support behaviour change
Action must be taken to integrate physical activity into daily life, not just to increase leisure time exercise
Sustainability of programmes is crucial to enable positive change in diet, activity and obesity levels over time
Political support, intersectoral collaboration and community participation are essential for success
Acting locally, even in national initiatives, allows programmes to be tailored to meet real needs, expectations and opportunities
All parts of the community must be reached—not just the motivated healthy
Programmes must be adequately resourced
Where appropriate, programmes should be integrated into existing initiatives (Box 1)
Programmes should be properly monitored, evaluated and documented. This is important for dissemination and transfer of experiences
Targeted outcomes for obesity prevention
Well-designed obesity prevention programmes have two types of targeted outcome—impact outcomes and process outcomes. It is important to understand that these outcomes cannot be achieved overnight—most will take years to achieve.
These are the ultimate targets of obesity prevention programmes. They should relate to the level of obesity in a population, for example:
to prevent increases in average population BMI
to reduce the incidence of new cases of obesity
to move toward an optimum average population BMI of 21–23 kg/m2
to reduce the prevalence of obesity
to reduce the disproportionately high prevalence of obesity among population subgroups
to reduce the prevalence of obesity in children
to reduce the prevalence of obesity-related health problems
Process outcomes related to food intake and physical activity
Process outcomes related to food intake and physical activity patterns are critical for ensuring that efforts to prevent obesity are on course. These guide short-term progress towards achievement of the long-term impact targets.
In setting process outcomes, it is recommended that each country consider the following population-based guidelines. These are common to national nutrition and health policies in a range of countries where chronic disease risk reduction is a priority. They should also promote energy balance whereby energy intake from food and drink is balanced with energy output through physical activity.
Food-based dietary guidelines: eat lots of fruit, vegetables, fish and starchy carbohydrate foods. Limit fatty, sugary and salty foods
Nutrient-based dietary guidelines: aim for about 10% energy from protein, 15–30% energy from fat, more than 50% energy from complex carbohydrates. Limit salt and alcohol intakes
Active living: for adults who are currently inactive or not regularly active, aim to accumulate 30 min or more of moderate intensity physical activity on most days of the week
Regular exercise: for adults who are already doing regular moderate activities, aim to include three bouts per week of vigorous intensity activity which lasts for at least 20 min
For countries where obesity levels and chronic disease are not yet high, it may be more appropriate to focus on preservation of healthy traditional food and activity practices when setting target process outcomes.
5. Potential solutions
Potential societal-level solutions
Settings and sectors offer practical opportunities for the implementation of comprehensive societal level strategies (Table 5).
Case studies, often implemented for reasons other than obesity prevention, give some idea about how these work in different countries and populations around the world. See Appendix 1 (available in on-line version) for example case studies related to different settings and sectors.
6. Tracking outcomes
The need for monitoring and evaluation
Evaluation is an essential tool for providing information about, and strengthening, obesity prevention programs. It helps to:
identify sub-groups of the population with particularly high or rising obesity prevalence
provide information about the implementation and effect of the programme
track progress in accomplishing goals and objectives
provide feedback to those involved in project planning to determine which parts of the programme are working well and which are not
make improvements or adjustments in the process of implementation
value the efforts of those involved
document experience gained from the project so it can be shared with others
Evaluation and monitoring principles
Evaluation should be considered from the outset and remain ongoing. It can be conducted on an intermediate-term as well as a long-term basis
For many countries with limited resources, intermediate-term process evaluation may be more feasible than long-term outcome evaluation, which can be costly and complex
Long-term outcome evaluation
Outcome evaluation is needed to measure whether, and to what extent, the goals of the intervention have been achieved.
The net impact of obesity prevention interventions can be assessed by shifts of the average population BMI, obesity prevalence and/or another indicator of obesity towards lower values (Box 2)
The time required to achieve an improvement in obesity levels is likely to be slow
Intermediate-term process evaluation
Process evaluation is needed to track the progress that is being made towards achieving the overall goals. It can be split into three main areas.
Impact on food and activity patterns
Given the time expected to see an effect on obesity levels, it is important to assess the impact of the intervention on food intake and physical activity patterns. See Box 3 for example indicators.
Impact on societal factors
Indicators related to diet and physical activity should provide the focus for evaluation. Many of the variables on the left hand side of Figure 8, such as schooling, transportation and urbanization, are of socio-economic nature and are routinely collected in countries.
Impact on individual factors
The impact of preventive action on individual factors can be assessed by shifts in knowledge, attitudes and beliefs related to physical activity, food intake, body size, body image and voluntary weight control.
7. Glossary of terms
Active living. Any moderate-intensity physical activity taken incidentally while performing other functions. Examples include walking to school and climbing the stairs.
Body mass index (BMI). A simple index of body fatness calculated by dividing body weight in kilograms by height in metres squared (kg/m2).
Disability adjusted life years (DALY). A comprehensive assessment of health status based on both disability and premature death data. One DALY is one lost year of healthy life.
Disease burden. See Disability Adjusted Life Years.
Economic costs of obesity. These can be broadly divided into direct and indirect costs. Direct costs relate to the medical costs of obesity within the health care system. They are usually calculated as the sum of the proportion of medical costs of co-morbidities that are attributable to obesity. Indirect costs are the value of lost output because of cessation or reduction of productivity caused by morbidity and mortality.
Indicator. A characteristic of an individual, population, or environment which is subject to measurement (directly or indirectly) and can be used to describe one or more aspects of the health of an individual or population.
Intersectoral collaboration. A recognized relationship between part or parts of different sectors of society which has been formed to take action to prevent obesity in a way that is more effective, efficient or sustainable than might be achieved by any one sector acting alone.
Moderate-intensity physical activity. Activity which increases a person's heart rate slightly and makes them feel warm, but does not make them get out of breath. Examples include brisk walking, cycling, dancing, swimming, washing the car, heavy housework and gardening.
Obesity prevalence. The proportion of a population that is obese, ie with a BMI >30 kg/m2.
Obesity. BMI greater than or equal to 30 kg/m2.
Overweight. BMI greater than or equal to 25 kg/m2.
Physical activity. Any bodily movement produced by skeletal muscles that results in energy expenditure. For the purpose of this report, it is an umbrella term that includes exercise, incidental activity, active living and sport.
Setting. The place or social context in which people engage in daily activities where environmental, organizational and personal factors interact to affect health and wellbeing. Examples include neighbourhoods, worksites, schools and homes.
Sustainable development. Development that meets the needs of the present without compromising the ability of future generations to meet their own needs. It incorporates many elements, and all sectors, including the health sector, which must contribute to achieve it.
Target outcome. The intended change in a characteristic of an individual, group or population which is attributable to a planned intervention or series of interventions. Impact outcomes relate to changes in obesity levels. Process outcomes relate to changes in the determinants of obesity levels, ie food intake and physical activity patterns.
Transitional country. A previously low-income country which is now undergoing rapid economic, nutritional and epidemiological transition. Examples include China, Brazil, Chile, Korea, Taiwan, Malaysia.
Undernutrition. BMI less than or equal to 18.5 kg/m2.
Vigorous-intensity physical activity. Activity which increases a person's heart rate substantially (around 70–80% of maximum heart rate) and makes them breath heavily. Examples include brisk hillwalking, running, cross-country skiing, football (soccer), and fast cycling.
8. Key References and Further reading
Allander E, Lindaho BIB. Why is prevention so difficult and slow? Scand J Soc Med 1997; 25: 145–148
Antipatis VJ, Kumanyika SK, Jeffery RW, Morabia A, Ritenbaugh C. Confidence of health professionals in public health approaches to obesity prevention. Int J Obes Relat Metab Disord 1999; 23: 1004–1006
Glenny AM, O'Meara S et al. The treatment and prevention of obesity: a systematic review of the literature. Int J Obes Relat Metab Disord 1997; 21: 715–737
James WPT. A public health approach to the problem of obesity. Int J Obes Relat Metab Disord 1995; 19(Suppl 3): S37–S45
Popkin BM. The obesity epidemic is a world-wide phenomenon. Nutr Rev 1998; 56: 106–114
Schooler C, Farquhar JW, Fortmann SP, Flora JA. Synthesis of findings and issues from community prevention trials. Ann Epidemiol 1997; 7(Suppl 7): S54–S68
Tansey G, Worsley A. The food system. A guide. Earthscan, 1996
Kumanyika S, Antipatis V, Jeffery R, Morabia A, Ritenbaugh C, James WPT. The International Obesity Task Force: its role in public health prevention. Appetite 1998; 31: 426–428
PHAPO working group. Caught in the causal web—a new perspective on social factors affecting obesity. Obesity, IASO/IOTF newsletter, Spring 1999; 10–11