The world population is becoming rounder, and each year the situation is worsening. The World Health Organization (WHO) believes that we are in the grip of a global epidemic, and it is estimated by the year 2020 obesity will be the single biggest killer on the planet.

Professor Philip James, Chairman of the International Obesity Task Force, said that “we now know that the biggest global health burden for the world is dietary in origin and is compounded by association with low physical activity levels. This is going to plague us for the next 30 years.”

Currently at least 300 million adults worldwide are obese — a body mass index (BMI) of over 30 — and over one billion are overweight (BMI of more than 27.3 percent for women and 27.8 percent or more for men). The problem affects virtually all ages and socioeconomic groups.

A Global Issue

Obesity rates have risen at least threefold since 1980 in some areas of North America, the UK, Eastern Europe, the Middle East, the Pacific Islands, Australasia and China. In many developing countries, obesity coexists with malnutrition: A survey of 83,000 Indian women found that although 33 percent were malnourished, 12 percent were overweight or obese. The adoption of industrialized foods and food preferences, together with drastically decreased physical activity levels are contributing to this growing problem.

Of particular concern is the increasing rate of child obesity. Health officials around the world have begun estimating each country’s rate. The Chinese government calculates that one in ten city-dwelling children is now obese. In Japan, obesity among nine-year-old children has tripled.

Why is this happening?

Obesity mainly is a result of changes in diet and physical activity. In the developing world the rise in obesity due to these factors is known as the ‘nutrition transition.’ Urban areas, being much further along in the transition than rural areas, experience higher rates of obesity. Cities offer a greater range of food, usually at lower prices, and city work often demands less physical exertion than rural work.

The developing world is likely to suffer a greater health burden from obesity. For example, the number of people with diabetes caused by obesity is estimated to double to 300 million between 1998 and 2025 — with three-quarters of that growth projected in the developing world. For nations whose economic and social resources are already stretched to the limit, the result could be disastrous.

What health problems are linked to obesity?

Compared to adults with normal weight, adults with a BMI greater than 30 are more likely to be diagnosed with coronary heart disease (CHD), hypertension, stroke, high cholesterol, gout, osteoarthritis, sleep problems, asthma, skin conditions and some types of cancer.

In June 1998 the American Heart Association announced that it was upgrading obesity to a ‘major risk factor’ for CHD. Obesity also is an important causal factor in type 2 diabetes, and it complicates management of the disease, making treatment less effective.

Psychological disorders which obesity may trigger include depression, eating disorders, distorted body image, and low self-esteem.

Obese people have been found several times to have higher rates of depression. For example, David A. Kats, MD and colleagues at the University of Wisconsin-Madison assessed quality of life in 2,931 patients with chronic health conditions including obesity. They found that clinical depression was highest in very obese participants (BMI over 35).

Other researchers also have identified an increase in depressive symptoms in very obese people. Evidence from the Swedish Obese Subjects (SOS) study indicates that clinically significant depression is three to four times higher in severely obese individuals than in similar non-obese individuals.

“Depression on a level indicating psychiatric morbidity was more often seen in the obese,” the authors, Professor Marianne Sullivan and her team from Sahlgrenska University Hospital, Sweden wrote in a journal article. They reported that the depression scores for obese people were as bad as, or worse than, those for patients with chronic pain.

Further data from a large community study supports a link. Robert E. Roberts, PhD., and colleagues at the University of Texas Health Science Center at Houston gathered data on 2,123 participants living in Alameda County. Taking into account factors such as social class, social support, chronic medical conditions and life events, they found that “obesity at baseline was associated with increased risk of depression five years later. The reverse was not true; depression did not increase the risk of future obesity.”

Some data have indicated that binge eating may explain, at least in part, the relationship observed between obesity and depression. This may be because binge eating could contribute to weight gain and obesity, which, in turn, may negatively affect mood. Furthermore, recurrent episodes of binge eating are extremely unpleasant for those who experience them, and may put the individual at higher risk of clinical depression.

The Impact on Health Care

Both the direct and indirect medical costs of obesity will become a major burden for health care systems around the world.

In the U.S., a 1998 study found that medical expenses attributed to both overweight and obesity accounted for 9.1 percent of total U.S. medical expenditure — possibly reaching $78.5 billion (the equivalent of nearly $100 billion today). Half of these costs were paid by Medicaid and Medicare.

Around the world, the WHO found the economic costs of obesity to be in the range of two to seven percent of total healthcare costs, as a conservative estimate.

What Is Being Done?

Despite soaring obesity rates, few effective obesity management systems are in place around the world.

The WHO began sounding the alarm in the 1990s, and stated that obesity is predominantly a “social and environmental disease.” They recommend a range of long-term strategies for groups at risk of obesity — an integrated, population-based approach, with support for healthy diets and regular exercise.

In reality, approaches vary widely between countries, with a general lack of comprehensive services. All too often obesity is not viewed as a serious medical condition. It tends to be treated only when another disease has developed.

Experts believe the most effective approach for weight loss in obese people is a diet aimed at reducing total energy intake; however, all but five percent of people who lose weight on a diet regain it all. Nevertheless the diet industry is worth $40 billion a year in the U.S. alone.

Certain high-risk patients are given weight-loss drugs, but these cannot be used long-term due to side effects such as high blood pressure, anxiety and restlessness. New drugs are being developed that may produce fewer side-effects.

Surgical options include gastric bypass, gastroplasty (which decreases stomach capacity with a band), jaw wiring and liposuction. But tackling obesity clearly will mean changing people’s lifestyles — encouraging them to eat more healthily and exercise more. Many efforts focus on children and schools to set in place healthy habits for life.


Garrow and Summerbell study

Centers for Disease Control and Prevention

PubMed articleInternational Obesity Task Force

American Obesity Association

Weight Control Information Network


BBC information on obesity

Economist story (requires subscription)

Katz, D. A. et al. Impact of obesity on health-related quality of life in patients with chronic illness. Journal of General Internal Medicine, Vol. 15, November 2000, pp. 789-96.

Sullivan, M. et al. Swedish obese subjects (SOS) – an intervention study of obesity. Baseline evaluation of health and psychosocial functioning in the first 1743 subjects examined. International Journal of Obesity and Related Metabolic Disorders, Vol. 17, September 1993, p. 503-12.

Roberts, R. E. et al. Prospective association between obesity and depression: evidence from the Alameda County Study. International Journal of Obesity and Related Metabolic Disorders, Vol. 27, April 2003, pp. 514-21.