'Sumo' rats are the result of a joint project between US and Indian scientists at the National Institute of Nutrition at Hyderabad.
The rats are said to contain an as yet undiscovered obesity gene that could lead to an understanding of human obesity.
"If, as we believe, this is a new obesity gene, it could have major implications," says Nappan Veettil Giridharan, deputy director of NIN, the key scientist responsible for developing the 'sumo' rats.
These rats also develop cataracts and tumors and their infertility is fully reversible by diet restriction. The rats have kinky tails, not seen in any other obese models.
Some information on the NIN is available here.