Following a low carb diet could cause serious health conditions, doctors in the US have warned.
Cheese was a significant part of the patient's diet
Medics from New York, writing in the Lancet, describe a 40-year-old woman on the Atkins diet who developed a serious blood condition.
Public health doctors writing in the journal said low carb diets were "far from healthy".
But a spokeswoman for the Atkins Foundation said the diet would not cause such health problems.
The patient treated by the New York team was obese.
She had been following the Atkins diet rigorously in order to lose weight and had taken recommended precautions, including using vitamins and other supplements.
She arrived at the emergency department of the Lennox Hill Hospital in New York one night in February 2004 after becoming increasingly short of breath and was taken into the intensive care unit.
Before her admission, the woman had lost appetite and felt nauseous, vomiting four to six times a day.
Tests confirmed ketoacidosis - a serious condition that occurs when dangerous levels of acidic substances called ketones build up in the blood.
They are produced in the liver when insulin levels fall due to starvation or diabetes.
In the case of this patient, doctors concluded that the Atkins diet was chiefly to blame.
Professor Klaus-Dieter Lessnau, who led the team from the New York School of Medicine, wrote: "Our patient had an underlying ketosis caused by the Atkins diet and developed severe ketoacidosis possibly when her oral intake was compromised from mild pancreatitis or gastroenteritis.
"This problem may become more recognised because this diet is becoming increasingly popular worldwide."
The Atkins diet suggests rapid weight loss by cutting carbohydrates out of a diet.
For a month before she fell ill, the woman had lived on meat, cheese and salads, said the doctors.
She monitored her urine twice daily using dipsticks.
During the period when she dieted, she lost around nine kilograms of weight.
Dr Lyn Steffen and Ms Jennifer Nettleton, from the University of Minnesota School of Public Health in Minneapolis, said: "Low carbohydrate diets for weight management are far from healthy, given their association with ketosis, constipation or diarrhoea, halitosis, headache, and general fatigue to name a few side-effects.
"These diets also increase the protein load to the kidneys and alter the acid balance in the body, which can result in loss of minerals from bone stores, thus compromising bone integrity."
They said "indisputable safety" was the most important factor when formulating prescriptions for weight loss, and added that "low carbohydrate diets currently fall short of this benchmark."
But Dr Abby Bloch, vice-president for programs and research at the Dr Robert C Atkins Foundation, told the BBC her diet could not have caused the woman's condition.
"Vomiting, from a clinical problem which isn't triggered by diet, would have led to the ketoacidosis."
She said millions of people were on low carb diets without experiencing health problems.
Dr Bloch added that "troublesome" and "inappropriate" comments had been made in the Lancet about claims regarding the ill-effects of low carbohydrate diets which had been disputed in many studies.