Willing to risk about $900 over 18 months?  I found this site yesterday that is supposed to be quite reputable.  You bet on yourself to lose weight. say $50 a month that you will lose X amount of weight by a certain date.  You can make a lot of money.  I've heard it's highly motivational to some people to keep going.  Prize money is "paid out" by the money lost by those who don't achieve their goals.  The front page has a calculator.

https://www.healthywage.com/weight-loss-bet/name-your-own-prize/?gclid=EAIaIQobChMI1OzA9p3s2gIVhSFpCh2ycwIXEAAYASAAEgLj_PD_BwE