Obesity may be defined as an abnormal growth of the adipose tissue due an enlargement of fat cell size (hypertrophic obesity) or an increase in fat cell number (hyperplastic obesity) or combination of both. Obesity is often expressed in terms of body mass index (BMI). Overweight is usually due to obesity but can arise from cause such as abnormal muscle development or fluid retention.
However, obese individuals differ not only in the amount of excess fat that they store, but also in the regional distribution of fat within the body. The distribution of fat induced by the weight gain affects the risk associated with obesity, and the kind of disease that results. It is useful therefore, to be able to distinguish between those at increased risk as a result of “abdominal fat distribution” or “android obesity” from those with the less serious “gynoid” fat distribution, in which fat is more evenly and peripherally distributed around the body.
Obesity is perhaps the most prevalent form of malnutrition, As a chronic disease, prevalent in both developed and developing countries, and the affecting children as well as adults, it is now so common that it is replacing the more traditional public health concerns including undernutrition. It is one of significant contributors to ill health. For industrialized countries, it has been suggested that such increase in body weight have been caused primarily by reduced levels of physical activity, rather than by changes in food intake or by other factors. It is extremely difficult to assess the size of the problem and compare the prevalence rates in different countries as no exact figures are available and also because the definitions of obesity are not standardized.
overweight and obesity are the fifth leading risk of global deaths. Worldwide, obesity has more than doubled since 1980. In 2008, more than 1.4 billion adults, 20 years and older, were overweight. Of these over 200 million men and nearly 300 million women were obese.
In 2012, more than 40 million children under 5 years of age were overweight. Once considered a high income country problem, overweight and obesity are now rising in low and middle income countries, particularly in urban settings. Close to 30 million overweight children are living in developing and 10 million in developed countries. Childhood obesity is associated with a higher chance of obesity, premature death and disability in adulthood, In addition, it is associated with future risk of increased breathing difficulties, increased risk of fractures, hypertension, early markers of cardiovascular disease, insulin resistance and psychological effects.
At least 3.4 million adults die each year as a result of being overweight or obese. In addition, 44 percent of the diabetes burden, 23 percent of ischemic heart disease burden and between 7 to 41 percent of certain cancer burdens are attributable to overweight and obesity. Overweight and obesity are linked to more deaths worldwide than underweight.