Severely obese individuals can loose weight with lifestyle modifications.

University of Pittsburg researchers studied 130 severely obese participants and found that diet combined with either initial or delayed initiation of physical activity resulted in significant weight loss one year later. Those who began the exercise immediately lost more weight at 6 months, but the delayed-exercisers almost caught up at 12 months (12 kg and 10 kg, respectively). This counters to old adage that the severely obese do not respond to lifestyle intervention. 

PositiveTip: Lifestyle interventions such as exercise and reduced-calorie diets do work!