“How often should an obese person go to the gym?”

It depends on the exercise that you do. I usually suggest as often as you can without increasing inflammation or risk of injury based on a person's size. Generally the most important thing is to get the nutrition part right. In some studies, losing weight is 80% based on what and how much someone consumes, and 20% exercise. I recommend everyone who battles obesity work with a bariatrician. Go to: https://obesitymedicine.org/find-obesity-treatment/ and you can find someone near you.