Hazel Kent, 40, of Bracknell, Berkshire, claims the operation is her only hope to lose weight.
Ms Kent lost seven-and-a-half stone (49kg) in 2001 after having a gastric band fitted but it had to be removed due to medical complications.
Berkshire East NHS PCT said Ms Kent's body mass index was not high enough.
Its guidelines state anyone undergoing the surgery should have a BMI of at least 50, while Ms Kent's is 37.8.
The trust, which has refused Ms Kent funding four times, added that other criteria had to be met in order for patients to have the operation, which costs £15,000.
It said the patient would have to have a secondary condition caused by being overweight or have failed to respond to all other treatments.
With thanks to www.bbc.co.uk
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