An individual is classed as being 'normal' weight, overweight or obese depending on the degree of fat in one's body. They form a continuum

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Overweight is the term given when the degree of 'fatness' is greater than normal, but less than obesity.

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For clinical purposes fatness is measured by a ratio called body mass index (BMI). 

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For Asian Indians, the upper limit of normal BMI* is 23

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Between 23 and 24.9 it is called overweight, and equal to or above 25 is obesity

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*BMI is calculated as the weight in kilogram divided by the height expressed in meters (kg/m squared)

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Essentially, body weight depends on the net balance between the energy a person ingests and the energy that is expended. This is a bald statement much like saying 'to win an election all one has to do is get one vote more than all other contestants'

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It is difficult to put the principle into practice: viz, to lose weight, reduce the energy consumed, along with increase in energy that is expended.

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The body has a complex network that resists a net negative balance of energy

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Yet, in the absence of safe and effective alternatives one tries to reduce the amount of food one consumes, which is the most important part of a weight loss programme.

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Physical exercise helps in maintaining the lost weight. 

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Without controlling ones diet, it is practically not possible to lose weight by physical exercise alone

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In rare conditions where the increased weight is a result of other underlying diseases, correcting them might lower the body weight. Such rare conditions are 'rare'

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When the body weight is so high (eg BMI=>40, or it is =>35, along with other disorders (eg type 2 diabetes, hypertension, sleep apnea, osteoarthritis, heart disease etc, bariatric surgery may be performed

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One must realise that bariatric surgery is not a golden bullet; it is associated with risks of surgery as well as other potential metabolic problems

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A considered decision must be made with a detailed discussion with the health care team

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Also remember that the BMI assumes a higher number is fat. In some cases it may not be: eg professional athletes with a lot of muscle may meet the BMI criteria without being overweight or obese; similarly when there is deem (excess fluid in the body as in renal or heart failure), the BMI criteria fails