The study addressed the issue of obesity through its medical description, elucidating its causes, damages, and treatments, with a focus on surgical obesity treatment. The study primarily discussed the impact of the principle of "no harm and no reciprocal harm" and its derived principles on the religious rulings regarding obesity surgeries, by balancing between the damages of obesity and the complications of the procedure on one hand, and between the complications of the procedure and its benefits on the other hand. The study answered two main questions, which are: What is the clinical definition of obesity, and what are the surgical treatments to get rid of it? What is the impact of the principle of "no harm and no reciprocal harm" on the religious ruling of obesity surgery? The study concluded that surgical treatments for obesity are performed for those with a body mass index (BMI) exceeding 40, or those with a BMI of 35 who are suffering from other serious illnesses. The impact of the principle of no harm and no reciprocal harm has appeared in the religious ruling of surgeries due to the severe damages caused by obesity on health, psychological, social, and economic levels, necessitating the removal of these damages through surgery, in accordance with the principles that (harm must be removed), (necessities permit prohibitions), (The need becomes a necessity, whether they are general or specific). The jurists also permitted this surgery based on the principle that (the more severe harm is removed by the lesser harm), and the principle that (if two harms coincide, the greater one should be prioritized to avoid the lesser one). Since the damages of obesity exceed those resulting from the surgical procedure, these complications are almost rare and transient, compared to the numerous and enduring benefits of the procedure. This led the jurists to permit these surgeries based on the principle that (minor harm is forgiven for the sake of greater benefit), and the principle that (transient harm is forgiven for the sake of enduring benefit), as well as the principle that (a realized benefit should not be forsaken for a hypothetical harm).