Extreme diets: Life on 800 calories a day

Her death made headlines around the world: Samantha Clowe, a 34-year-old British woman, died suddenly this fall from a previously undiagnosed heart condition. At the time of her death, Clowe was following a plan called LighterLife, a very low-calorie diet designed to help obese and severely obese patients lose weight.

She was consuming 530 calories a day.

"Samantha came to LighterLife with a BMI of 37, weighing more than 17 stone [238 pounds]," says a spokesperson for the company. "Although she managed to lose 3 stone [42 pounds], her health may have already been compromised." An inquest determined that Clowe most likely died from cardiac arrhythmia but could not determine what role, if any, Clowe's diet played in the development of her condition, only that her death "may be related to her low calorie diet and weight loss."

Very low-calorie diets have been used to help obese and severely obese patients lose weight for more than two decades. "Next to bariatric surgery, nothing is more effective for weight loss than a VLCD, including pills and other diets," says Dr. John Hernried, medical director for OTC Medical Weight Loss Group, a weight-loss clinic in California.

But the diet "is not indicated for someone who wants to lose 10 pounds." Most programs screen potential participants to ensure they are psychologically and medically stable enough to begin the process.