Prevalence of obesity is increasing at such an astonishing rate that it is emerging as an important public health problem. To get insight into the development of obesity, this chapter presents a Calorie balance sheet of energy input and energy expenditure. The WHY BOX answers a logical question \"If weight loss is attempted by ‘calorie restriction alone’ why weight loss does not occur by simple equation of 3500 calorie deficit = 0.45 kg reduction in body fat?\" Three possible approaches to deal with obesity are discussed: Strategy No. 1: Eat less, weigh less; Strategy No. 2 Spend more, weighs less; Strategy No. 3 Getting the best of both worlds: Diet AND Exercise. MYTH section bursts three myths found commonly in obese people \"Some foods or combination of foods can help ‘burn off’ or ‘melt off’ fat in the body”. \"Crash diet or starvation is a guaranteed way of losing body weight”. and \"Weight training is not a useful exercise to reduce body weight”. You will find some useful tips in the section \'Let us chew certain facts about diet.\' Solutions to increase body weight are given in the write-up \'Weight gain: An equally tricky situation\'. The treatise on weight management ends with \'Place of anti obesity drugs’.