It's a weight loss solution that seemed too good to be true: Stop exercising, eat a third of your normal daily calories, and shed the pounds without a single hunger pang.

But Grainne O'Flynn, 56, of Los Gatos, needed to lose weight. And, after seeing few results from diet and exercise, O'Flynn was ready to try something different.

For her, it was hCG, a controversial short-term, 500-calorie a day diet that includes specific whole foods and daily injections of human chorionic gonadotropin, a hormone found in pregnant women's urine. Proponents of the diet say hCG triggers the body to metabolize stored fat as energy, though detractors warn that like any get-thin-quick diet, it's not a healthy way to lose weight.

The diet is not new. It was developed in the 1950s by British physician A.T.W. Simeons. After discovering its effect in pregnancy, Simeons administered hCG to his obese patients and watched their weight plummet in conjunction with the diet of lean proteins and low-carbohydrate fruits and vegetables.

After a series of clinical trials disputed the effectiveness of Simeons' method -- his results could not be replicated -- it fell from favor in the 1970s. Decades later, critics still insist the hormone is but a placebo in a starvation diet.

Still, Bay Area physicians who have helped thousands lose weight say their clinical experience can not be ignored. Nor can the supposed perks that come with injections, including decreased appetite, muscle retention and spot reduction in the stomach and thighs, they say.

Under the care of Saratoga's John Tang, a Stanford-trained physician and anti-aging specialist, O'Flynn lost 26 pounds. Much to her surprise, she didn't starve on 500 calories a day. She "felt great."

"I began thinking differently about food portions, because for the first time in my life I had to weigh everything," she says. "I rarely hype up anything. But this worked for me."

The Food and Drug Administration has not approved hCG for weight loss, but physicians are permitted to use it "off-label." The American Society of Bariatric Physicians also does not condone Simeons' methods nor the use of hCG for weight loss.

A typical cycle of the diet, which can cost up to $1,000, lasts six weeks and includes supplements for energy, the hCG supply and syringes.

In general, everyone on the diet tends to feel better because they are learning to eat right and avoid junk food, Tang says. Once the cycle is over, patients transition to a maintenance diet of 1,000 to 1,500 calories a day. Same foods, just more of them.

From a weight loss perspective, hCG sounds far-fetched: First, it suppresses appetite in most people who take it. Second, by releasing stored fat, muscle is spared, Tang says. And, because the fat is from deep inside the body -- people lose the most around the hips and stomach -- the skin tends to hug the body rather than sag afterward. Also, because caloric intake is so low you're instructed not to exercise on the diet.

Registered dietitian Nora Norback of Kaiser Permanente's Richmond Medical Center doesn't buy any of it. Anyone who eats 500 calories a day will lose weight, but not without major risks to the liver and gall bladder, she says. According to the Mayo Clinic, hCG can also cause headache, fatigue, irritability, male breast enlargement and a mild stimulatory effect on the ovaries.

"This is not a healthy way to lose weight," Norback says. "Sound nutrition. Physical activity. Those are."

Fans of hCG say side effects are unlikely because the amount used is miniscule: About 250 units or less as opposed to the 400,000 units pregnant women have coursing in their bodies daily, says Lisa Kang, a San Francisco board certified general surgeon who has treated 1,500 patients since 2009. For those who are curious, the hCG is extracted from the urine then sterilized and purified in a lab before it is sold to pharmacies.

Robert Baron, director of UCSF's Weight Management Program, also says the claims surrounding hCG are "aspirational." As for the diet itself: "It's probably not that dangerous because it's so short-term," says Baron, a professor of medicine.

Very low calorie diets, known as VLCD, are common in bariatrics, though the daily calories are higher than on the hCG diet and typically come as meal replacements, he says.

"Eight hundred calories with adequate protein is a more evidence-based approach," Baron adds.

Also, very low calorie diets are not for everyone, he says. Typical candidates are dangerously unhealthy and need to lose a lot of weight -- fast. Perhaps they are severely diabetic, or require knee replacement, but the surgeon can't successfully operate until they lose 50 pounds.

But Lynne Mielke, a board certified physician in Pleasanton, recommends hCG to anyone who needs to lose more than 15 pounds. Mielke, who specializes in integrative medicine, was skeptical of the hCG diet. So, before she offered it to her patients, she tried it on herself two years ago.

"If I had tried the (low calorie) diet without the hCG, I would've been on the floor from hunger. But it had this astonishing ability to suppress my appetite. And it was so motivating to see the pounds just melt, " says Mielke, who lost a total of 40 pounds.

Ann Brunori can relate. She wrapped up her hCG cycle in August and is currently in maintenance mode. But it wasn't as easy as everyone says, at least in the beginning. Until her body acclimated, the 65-year-old San Franciscan felt the hunger pangs. Appetite suppressants didn't work. They kept her up at night.

While Brunori didn't experience any of the other alleged benefits of being on hCG, she did meet her goal: She lost 30 pounds and "feels great."
"It's been a re-education of eating," she says. "I just hope I can stick with it."

history of hCG diet
In the 1950s, British physician A.T.W. Simeons discovered that, during pregnancy, hCG helped mobilize the body's abnormal fat into the circulation.

When combined with a restricted, low-calorie diet of lean proteins and specific fruits and vegetables, he found that his obese patients lost significant weight. In 1954, Simeons published his findings, "Pounds and Inches," in the medical journal, Lancet.

The controversial diet fell out of favor in the 1970s.

what you eat
Where do the 500 daily calories come from? Most physicians follow hCG diet founder A.T.W. Simeons' list of approved foods, which include:

Two meals consisting of: About four ounces of lean protein (such as chicken breast, steak, or shrimp), two cups of vegetables (including spinach, asparagus, or cabbage), and one piece of fruit (such as a medium-sized apple or orange or 10 medium strawberries). For a carbohydrate, one Grissini breadstick or plain Melba toast is allowed.

Breakfast: Coffee or black or green tea in any quantity.

Beverages: Two liters a day of spring water, tea, or coffee.