You may be looking to participate in a weight loss study. Many of these studies offer compensation, and it could be a study to test a new drug, a new diet, or a new lifestyle.
There are several websites that provide a list of weight loss and obesity studies and clinical trials all across the United States.
Here are some of these sites;
Anschutz Health & Wellness
Consumer Guide to Bariatric Surgery
Paid Clinical Trials
Hopefully, you will find a weight loss clinical trial in your area.