The Mayo Clinic reports that gastric bypass surgery is an effective means of controlling one's weight, and involves creating a small pouch from the stomach that bypasses the rest of the stomach and some of the small intestine. This means that one simply can't eat nearly as much as they used to, as their digestive tract has been reduced in size, making feelings of satiation arrive much faster.
Although there hasn't been an official word regarding Margaret Johnson's current status at the time of this writing, TV Shows Ace posted what appears to be a social media response from Johnson's mother, Millie, which said, "I'm so sorry we haven't updated y'all on Margaret Johnson's progress. We are hopefully on that road to recovery this time. It has been an uphill battle non-stop since her surgery. In and out of the hospital and rehab many times since her surgery day! I will tell you that in nine months since she started her diet she has lost a total of over 340 lbs! Prayers are always appreciated. She still has a long road to go!"
This is fantastic news, considering that Us Weekly notes that 10 people who appeared on the show have died as of August 10, 2021. Hopefully, Millie's update means we will soon get an official appearance from Johnson in the spin-off series "My 600-lb Life: Where Are They Now?" to highlight her progress.