He told me: 'I don't think I'll make it through the night. I love you and I always will.'
Robert featured as a part of the American reality TV show My 600lb Life on the TLC network, with the episode due to air this weekend.
He had been on the weight loss plan for five months and had already dropped 24 stone and 4lbs in that time.
Buchel had been forced to move to Houston, Texas, with his fiancée Kathryn Lemanski so that he could be closely monitored by the bariatric surgeon Dr Younan Nowzaradan.
During their journey to Houston, Robert had to be rescued by paramedics after being unable to help himself after falling over.
Just months into his stay in Houston, Robert regained his ability to walk and was soon down to 39 stone, 1lb.
He then underwent surgery to remove the lymphedema mass on the right of his body, however, this left him with a crippling addiction to painkillers.
Despite being told not to use the medication by Dr Nowzardan, Robert admitted that he felt depressed and couldn't stand the pain anymore, and even resorted to tearing at his stitches to get more painkillers.
Kathryn explains how difficult this period was:
It's like a switch has been flipped.
He's been nasty since the surgery because he can't get the drugs.
In the weeks leading up to his heart attack, Robert had reportedly refused to exercise despite being back in rehab.
According to the Mail, Robert and Kathryn were due to be married next year.
I lost my best friend and the person I was supposed to spend the rest of my life with.