Obesity is a global problem. According to W.H.O. estimates the number of obese people worldwide has already exceeded the number of people with undernutrition. Today, increasing incidence of obesity is reflected in the form of increased morbidity, shortened life expectancy and premature mortality.

Obesity and overweight are common expressions used to describe fat, heavy individuals. Infact, obesity and overweight and are relative terms but not synonymous.

• An individual is considered to be overweight when the body weight is 10-20% above the desirable body weight.
• Whereas if the body weight is 20% or more above the desirable body weight the person is considered to be obese.

Our body weight is a sum total of the individual weights of :

• Bones
• Muscles
• Organs
• Body fluids
• Adipose tissues (fat)

Most of these components undergo normal changes due to growth, nutrition and physical activity, reproduction and ageing. Water accounts for 60 - 65% of the total body weight. Changes in the water level inside the body may lead to fluctuations in body weight.

Increase or decrease in the amount of fat accounts for true weight gain or weight loss. Fat deposits are located mainly under the skin. It increases either by increasing the size of cells already present (scientifically known as hypertrophy) or by an increase in the number of cells (hyperplasia). In most cases obesity is due to hypertrophy. The fat depots in the body can grow to an extent of 1000 times through hypertrophy.

Normal amounts of fat in the body is not only harmless, but is essential as :

• It acts as an energy store for the body.
• It provides insulation against extreme temperatures.
• It helps in shock absorption to protect vital organs from trauma.
• It is the raw material for building cell wall  and many chemicals required by the body.

It is excess fat that we wish to avoid. What constitutes excess fat is still a matter of debate at the highest medical circles. Fortunately, for routine life, some clear cut definitions are available, that suffice for most needs.