The public health impact of obesity

The prevalence of obesity (severe overweight) has been increasing in western societies during the last decades. Epidemiological studies to the public health impact of obesity are therefore warranted. This thesis aimed at describing the long-term and recent time trends of obesity in the Netherlands, and to explore the relations between obesity, mortality, morbidity, and disability.

The prevalence of obesity, body mass index (BMI)≥30.0 kg/m ², increased steadily in Dutch adults between 1974 and 1997. Between 1993 and 1997, the prevalence of obesity was estimated at 9% among men and at 10% among men aged 20-59 years, based on data from the Dutch MORGEN-project. Levels of waist circumference increased more over time and showed even greater seasonal variation than BMI.

Obesity measured by BMI was related to increased all-cause mortality in men who never smoked, although relative risks seemed to decrease somewhat with ageing in European men from the Seven Countries Study. Levels of waist circumference identified more men over 55 years of age who never smoked with increased risk of mortality than levels of BMI in the Rotterdam Study.

Obesity was related to hospitalisation for coronary heart disease and to medication for chronic conditions in Finnish men and women from the Social Insurance Institution's Mobile Clinic study. In the Mini-Finland Health Survey, obesity was associated with the presence of osteoarthritis, low back pain, shoulder joint impairment and neck pain. In addition, obesity was associated with work disability during a 15 years follow-up and to the presence of difficulties in daily life activities. Relative risks of obesity for morbidity and disability were highest in the youngest Finnish adults studied, and exceeded the relative risk for mortality.

Prevention of weight gain (<0.5 kg/year) during a period of ten years, could prevent 26,000 new cases of knee osteoarthritis and 19,000 new cases of work disability in the Dutch working aged population.

Although obesity was related to increased mortality, obese Finns had more unhealthy life years than Finns with normal weight. During a maximal follow-up period of 15 years until age 65 years, obese men had 0.5, 0.4 and 1.7 extra years of work disability, coronary heart disease and morbidity leading to chronic medication, respectively. Obese women suffered respectively 0.5, 0.4 and 1.3 extra years from these conditions.

This thesis provides new evidence based on large epidemiological studies that weight gain prevention programs should get high priority on both the scientific and the political agenda.