Fasting or crash dieting: Dangerous to your health?

CNN:

Research suggests rapid weight loss can slow your metabolism, leading to future weight gain, and deprive your body of essential nutrients. What's more, crash diets can weaken your immune system and increase your risk of dehydration, heart palpitations, and cardiac stress.

"A crash diet once won't hurt your heart," Dr. Rosenfeld says. "But crash dieting repeatedly increases the risk of heart attacks."

Bacon adds that long-term calorie-cutting can eventually lead to heart muscle loss. "Yo-yo dieting can also damage your blood vessels. All that shrinking and growing causes micro tears that create a setup for atherosclerosis and other types of heart disease," she says.

The article continues:

Experts have known for decades that extended crash diets can be dangerous -- especially when the diets become a fad.

In the late 1970s, an osteopath named Robert Linn published "The Last Chance Diet," a best seller that advocated a miraculous "liquid protein diet." Following the lead of their favorite celebrities, millions of people bought quarts of Dr. Linn's liquid formula and embraced the diet (or one of many copycat versions), averaging just 300 to 400 calories a day.

The diet seemed to work wonders -- some people reported losing as many as 10 pounds a week on the formula. But then the news of sudden deaths began to trickle in.

An investigation led by the Food and Drug Administration turned up nearly 60 deaths among liquid dieters. Although some of the deaths occurred in people with underlying diseases such as atherosclerosis (and therefore could have been coincidental), government researchers who examined otherwise healthy dieters who died of ventricular arrhythmias found that the pattern of deaths suggested "the effects of protein-calorie malnutrition on the heart," including atrophy of the heart muscle.

Conceivably there is a right way and a wrong way to substantially reduce caloric intake.  In other words, certain approaches are likely more risky than others.   But which ones?

Muscle loss appears to be the problem.