Studies of interest were identified by systematic searches of MEDLINE and EMBASE for all 191 countries of the world with the keywords “BMI”, and “obesity” each paired with “cardiovascular disease”, “hyperlipidaemia”, “cholesterol”, “stroke”, “ischaemic heart disease”, “osteoarthritis,” “diabetes mellitus type 2”, “cerebrovascular disease”, and in combination with each country's name. We contacted WHO Regional Officers for help with searches and governments and individuals in searches for
SeminarObesity
Section snippets
Life expectancy
Even 50 years ago, men and women taking out insurance policies were known to be likely to die early if they were overweight and especially if they were obese when young.13 Obesity has more recently been shown to decrease life expectancy by 7 years at the age of 40 years.14 The increase in risk of death with each unit increase in BMI declines progressively with age but remains substantial until the age-group of 75 years and older.15 Thus, the UK Government now estimates that a BM'I of 25·0 kg/m2
Disease burden from excess weight in adults
Detailed estimates of the years of ill health and lives lost between the ages of 30 years and 75 years because of excess weight are shown for the subregions of the world in figure 2. These predictions are based on detailed estimates of the prevalence of various disorders and deaths from them, the prevalence of high BMI according to age, and the proportion of the disease burden attributable to the excess weight.5 Cardiovascular disease dominates, followed by diabetes and some cancers, especially
Fat distribution
Many of the comorbidities of obesity are reflected in the so-called metabolic syndrome, originally defined arbitrarily by WHO on the basis of insulin resistance with other features of obesity21 or pragmatically in the USA22 on the basis of three of five features: large waist circumference, abnormal concentrations of triglycerides, HDL cholesterol, and fasting glucose, and hypertension. Lower waist circumference cut-off points for Asian populations have been used in Asian analyses of the
Hypertension
The risk of hypertension is up to five times higher among obese people than among those of normal weight,29 the variability in response reflecting differential genetic susceptibility as well as dietary factors. Up to two-thirds of cases of hypertension are linked to excess weight,30 and cross-sectional population surveys31 suggest that more than 85% of hypertension arises in individuals with BMI values above 25 kg/m2. The increase in blood pressure with excess weight gain arises partly because
Coronary artery disease and strokes
Dyslipidaemia progressively develops as BMI increases from 21 kg/m2 with a rise in proatheromatous, dense, small-particle-sized LDL. This change increases the risk of coronary heart disease by 3·6 times. With low HDL concentrations, as well as high concentrations of triglycerides, CHD risk increases.40 The combined effect of dietary saturated and trans fatty acids on plasma lipids is amplified by the lack of n-3 long-chain fatty acids, which have complex competitive effects with the more
Diabetes
The relation between obesity and type 2 diabetes is so close that Sims and co-workers coined the term “diabesity” in the 1970s, when they showed that in young men with no family history of diabetes who were overfed for 6 months BMI increased to 28·0 kg/m2 and there were reversible rises in fasting concentrations of insulin, glucose, and triglycerides, and impaired glucose tolerance.45 Stevens and colleagues46 showed that around 90% of individuals who develop type 2 diabetes have BMI higher than
Imprinting of metabolic control in fetal life and early childhood
Worldwide analysis of diabetes shows that four of the five countries with the most cases are in Asia,48 with the risks of diabetes increasing from very low BMI. Clinicians must therefore be more proactive and alert to the possibility of impaired glucose tolerance and diabetes even at BMI values of around 23·0 kg/m2 when there is even slight abdominal obesity. In the most deprived areas of India, 14% of adults have diabetes and further 18% have glucose intolerance; on the basis of Chinese
Respiratory effects
People with pre-existing respiratory disease can be severely handicapped by weight gain: resting metabolic rates and movement costs are higher, but the physical effect of thoracic and abdominal fat restricts vital capacity and can be severely debilitating. Respiratory complications such as atelectasis and infection readily occur after anaesthesia. Whether obesity specifically induces bronchospasm is less clear, but overweight patients with asthma are further burdened, and their clinical
Cancers and reproductive abnormalities
Obesity is one of the most important known preventable causes of cancer. About 10% of all cancer deaths among non-smokers are related to obesity. The WHO International Agency for Research on Cancer56 estimated that overweight and inactivity account for a quarter to a third of cancers of the breast, colon, endometrium, kidney, and oesophagus. The underlying mechanisms are difficult to define. Acid reflux, due to abdominal bulk, contributes to oesophageal cancer, and colon cancer has been linked
Arthritis
That obesity leads to joint pain and arthritis of the knees and hips is not surprising, but the involvement of the carpometacarpal joints of the hand63 implies a metabolic contribution. Hyperuricaemia and gout are well-recognised features of both weight gain65 and the metabolic syndrome.
Non-alcoholic steatohepatitis
The prevalence of non-alcoholic steatohepatitis is increasing rapidly in more developed countries as part of the obesity epidemic. It is set to become one of the most common causes of end-stage liver failure in more developed countries, because it progresses from benign fatty changes to cirrhosis, portal hypertension, and hepatocellular carcinoma.66 The changes in liver histology seen in alcoholic disease are also typical of non-alcoholic steatohepatitis, but the aetiological factors are
Psychological features of obesity
Obesity was a sign of wealth and wellbeing in the past and still is in many parts of Africa, particularly since the HIV epidemic began. Care is needed to distinguish the social from the pathophysiological consequences of weight gain. In affluent societies and many Asian countries, slenderness is now the ideal, so individuals gaining weight, especially women, feel increasingly unacceptable and become anxious and depressed and can develop obsessive behaviours as they attempt to deal with their
Weight gain despite good physiological control of intake
Despite the obesity epidemic, individuals have extraordinarily fine control of their food intake on a weekly if not daily basis. Although there are unpredictable variations in daily intake in response to social events, and smaller fluctuations in energy output from changes in physical activity, body energy stores remain fairly constant. A weight gain of 0·5–1·0 kg in a year amounts to 3500–7000 kcal (14·6–29·3 MJ), implying an error in the regulation of food intake of less than 0·5% of average
Physical inactivity
Many studies have shown the relation between sedentary lifestyle and weight gain, but reliable direct measures of physical activity are only just emerging.76 Nevertheless, the secular decline in physical activity is obvious. Morris and colleagues showed more than 50 years ago77, 78 that vigorous exercise was crucial to cardiovascular health, but highly sedentary adults now derive benefit from even slight exertion.79 Exercise has many benefits, from psychological to physical, independent of its
Changes in daily food intake patterns
Short-term regulation of food intake is readily overcome by sudden increases in the energy density of food, for example by fat-rich evening meals that allow no compensatory adjustments until the next day.81 Sugar-rich drinks also circumvent the meal-based regulation of appetite.82 Foods with higher energy density—those rich in fats, extracted sugars, and refined starches—are unwittingly consumed in greater amounts, the density rather than the macronutrient content being the determinant of
Drugs
An increasing number of drugs are now being documented as causing weight gain (panel 2).95
Assessment and management
Despite the plethora of diet books and heavily promoted schemes for effortless and rapid weight loss, the escalating epidemic of obesity shows the failure of these approaches. The medical issue is now how to help transform patients' lives in the long-term when they are constantly distracted and disheartened by the claims for miracle cures. Patients need to create a micro-environment as a buffer against the all-pervading toxic environment, and the greater the genetic contribution to the
Dietary management
Management of the diet is much neglected by doctors and even misinterpreted by dietitians if energy intake is based on dietary history. The weight conscious and the obese systematically underestimate intake. Intake is better predicted by estimation of the patient's energy expenditure from their sex, age, weight, and crude classification of exercise patterns.104 This approach together with an individualised diet with an energy deficit of 500–600 kcal (2·09–2·51 MJ) is almost universally used in
Pharmacotherapy and surgery
Objections to pharmacotherapy linger, stimulated by memories of cocktails of diuretics, thyroid extract, and amphetamines combined with barbiturates. These concerns were fuelled by the withdrawal of fenfluramine and mixtures of ephedrine and caffeine,110, 111 which has led to a rigorous demand for evidence of efficacy when obesity drugs are evaluated. The only agents currently accepted by most regulatory agencies on the basis of extensive data are orlistat and sibutramine; rimonabant is
How are health-care systems going to cope with the obesity epidemic?
No health-service system has yet developed a useful strategy for managing the huge numbers of overweight and obese people in the community. Nursing, dietetic, and physical-activity expertise and collaboration with public and private community slimming groups are needed. The challenge of prevention as well as managing the millions already affected is overwhelming.120, 121 The challenge to think in novel ways was also emphasised by the new WHO global agreement122 to develop strategies to deal
Search strategy and selection criteria
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