Jon Brower Minnoch at 635 kg was the heaviest man before he died in 1983.During his lifetime, he lost about 419 kg which is most weight loss ever documented. Manuel Uribe from Mexico was 597 kg before he lost 225 kg over 2-year period. He is also the heaviest man alive.
Carol Yager is an American woman whose peak weight was 545 kg before she lost 236 kg with natural means in 3 months. Rosalie Bradford again from US is a Guinness world record holder for the most weight lost by a woman - i.e., 415.9 kg but passed away in 2006.