Gastric bypass surgery can lead to significant weight loss for individuals who undergo the procedure. On average, patients can expect to lose about 60-70% of their excess body weight within the first year following the surgery. However, the actual weight loss can vary depending on various factors such as the individual's starting weight, adherence to post-surgery guidelines, and commitment to adopting healthy lifestyle habits. It's important to note that gastric bypass is not a quick fix and requires long-term commitment to dietary and lifestyle changes to achieve and maintain weight loss goals.