Individuals suffering from severe obesity do not have sufficient calorie burning capacity to exercise and induce sustainable weight loss. The same amount of exercise for them is much harder than for those with normal body mass index (BMI) .
Several hormones decide the amount of fat to be stored in the body. Unhealthy diet, irregular food habits, lack of exercise, lack of sleep and stress trigger these hormones and reset the fat value to higher level.
Individuals with mild obesity can lose weight by removing these triggers and maintaining healthy lifestyle. But if obesity is severe (BMI ≥ 30 kg/m2), even if the triggers are removed there won’t be weight loss because body got adopted to a higher weight level. Even if there is a weight loss, lost weight will come back. When they try to lose weight, body hormones fight back and replace the lost weight, by reducing metabolism in order to conserve fat. They also increase hunger, making them to eat more. So weight bounces back.
20 out of 100 individuals with severe obesity, never lose weight inspite trying hard. Remaning 80 individuals lose weight but 76 of them regain weight. So failure rate is 96% in long run. So individuals with severe obesity needs bariatric surgeries which alter these hormones and reset the fat mass to a lower level.