Let’s Talk about Diets

By Heather on Aug 27, 2005 | Reply

July 24, 2000 — When Michelle Murdock and her husband sit down for dinner together, they never eat the same meal. While she doesn’t eat meat, her husband eats it often. She loves peanut butter; he avoids it. She shies away from dairy products, while he consumes all the milk and cheese he wants. Why do their menus vary so widely? It’s not because they have different tastes — rather, they have different blood types. (Hers is type A; his is type B.)

The Murdocks follow the “Eat Right for Your Type” diet, which encourages people to consume certain foods and shun others based on their status of A, B, AB, or O. Michelle, 29, has been on the diet for almost two years and is still enthused. “I lost about 35 pounds the first year I was on it,” she says. ”I have since maintained a healthy weight.” She says she has the energy of a teenager.

Who’d think a diet would be based on blood type? The theory is the brainchild of Peter J. D’Adamo, ND, a naturopathic physician in Stamford, Conn., who touted the program in his 1996 book, Eat Right for Your Type, which gave the diet its name. Eating this way can not only keep you healthy and help you lose weight, D’Adamo says, but not eating this way can harm you, perhaps setting you up for digestive problems or serious ailments, including cancer. Not everyone agrees with D’Adamo — the diet is roundly criticized by most mainstream nutritionists and medical doctors for the lack of published evidence showing it works.

But criticism is not enough to deter as many as two million people who follow the diet (the figure comes from D’Adamo and is based on visitors to his web site and his private practice). These blood-type diet fans don’t mention feeling deprived because of food restrictions, but talk instead about how good they feel. Many, like the Murdocks, embrace the diet as a new lifestyle.

The Diet’s Theory

One reason for these dieters’ enthusiasm is that there’s no counting of calories or fat grams. Instead, the diet emphasizes eating certain foods, in any quantity you’d like. For instance, Type O’s are advised to eat meat but no grains. Type A’s should be vegetarians. Type B’s can eat the most varied diet, including meat and dairy products. And Type AB’s should eat some meat, but lay off cured or smoked meats.

Why are certain foods specified for each blood type? D’Adamo believes that lectins, proteins found in foods, can wreak havoc in the body. If you eat a food containing lectins that are not compatible with your blood type, he says, the lectins can target an organ or system in the body. This can adversely affect blood cells in the area and possibly cause disease, including kidney disease and cancer. However, these negative effects can be avoided by focusing on foods that mesh with your blood type, D’Adamo says.

D’Adamo also theorizes that a person’s ability to digest foods varies depending on blood type. For instance, he claims that Type O’s can efficiently digest meats because they tend to have high levels of stomach acid. Type A’s, he says, have low stomach acid and store meat as fat.

D’Adamo bases his theories on research he’s conducted since the early 1990s on the connections among blood type, food, and disease. He says his research builds on work done by his father, a naturopathic physician who drew on his observations of his patients. Based on those observations, D’Adamo also suggests that type O’s should exercise vigorously, B’s moderately, and A’s gently. AB’s, he says, need calming exercise.

Where’s the Beef?

While D’Adamo acknowledges that there is no scientific study that demonstrates that his program helps with weight loss or disease prevention, he has posted 52 pages of references on his web site (www.dadamo.com) that he says back up his belief that blood type may be related to disease. But many mainstream nutritionists and medical doctors roundly criticize the program and urge their patients not to follow it. These critics cite the lack of published studies showing that the diet works.

“My initial skepticism of the diet plan was supported by the complete lack of scientific foundation [in D'Adamo's book],” says John McMahon, ND, a naturopathic physician in Wilton, Conn. “I believe he feels he is doing people a favor, but I think he is seriously mistaken.”

Adds John Foreyt, PhD, a weight loss researcher at the Baylor College of Medicine in Houston: “I know of no plausible rationale behind the diet.”

Critics also quibble with D’Adamo’s theory that there is an association between certain blood types and specific diseases (which he says can be tempered by eating certain foods). Though this theory has long been talked about and investigated, no conclusions have been reached, says Andrea Wiley, PhD, an associate professor of anthropology at James Madison University in Harrisonburg, Va. It would be a huge leap, she adds, to say with certainty that a person with a specific blood type will probably contract a specific disease — as D’Adamo claims when justifying his diet.

Potential for Harm?

In fact, some experts go so far as to say the diet may be harmful. Michael Klaper, MD, a general practice physician in Pukalani, Hawaii, says eating large quantities of meat, for instance, is discouraged by most diet plans, because the fat can add up and it may leave you too full to eat other crucial foods. In another example, a lactose-intolerant Type B, who would be encouraged by D’Adamo’s plan to eat a variety of dairy foods, would have significant difficulties, Klaper says.

One East Coast physician interviewed for this story (who didn’t want to be quoted directly) says he has recently cared for three patients who were adversely affected after following the blood-type plan for a few months. One gained weight; another experienced joint pain. A third had an increase in blood cholesterol, from a respectable 183 to an undesirable level of 272 (over 200 is considered abnormal).

Even supporters of the diet say it is difficult to stay within its confines, given the long list of foods to avoid. For instance, the diet advocates that type B’s forgo shrimp, pork, chicken, ice cream, American cheese, peanuts, black beans, granola, whole wheat bread, wild rice, and tomatoes, among many other foods. If family members have different blood types, following the diet can be even more difficult.

Not Proven, But Still Popular

Like many other scientists, Wiley is puzzled as to why the blood-type diet has gained such a following. “Dieting is one of those things people feel desperate about,” she says. “The blood-type diet sounds more scientific [than some others].” And that, she says, could help explain why it has been embraced even by people who don’t generally follow fad diets.

Michelle Murdock, for one, plans to stay on the blood-type diet for life. She has a strong family history of colon cancer, ****** cancer, diabetes, and heart disease and hopes that following the diet — despite the inconvenience — will reduce her risk of developing these ailments. The few meals she, her husband, and daughter can eat together are sushi, some vegetable dishes, certain soups, and fish. “But we have gotten used to it,” she says.

Quack Diet Red Flags

Lose that weight — you know you should. But the sheer numbers of weight loss programs sometimes confuse the issue.

The cabbage diet! The rice diet! The blood type diet! Atkins! South Beach! No carb! Low carb! There’s even a Jesus diet (sans loaves and fishes).

“People who want to lose weight are a very vulnerable group because they’re very frustrated,” Kathleen Zelman, MPH, RD/LD, director of nutrition for the WebMD Weight Loss Clinic, tells WebMD. “Weight loss is hard, and everybody is looking for a silver bullet.”

How can you discern which weight loss claims are true or false? Here’s some advice from Zelman and from the Federal Trade Commission:

Does the diet promote rapid weight loss?

That’s a clear signal it’s unrealistic, says Zelman. When you start a diet, water weight is the first to go, she explains. If you lose much more than two pounds a week, you’re drawing from both fat and muscles. That’s not good, because muscle is one big factor that controls your metabolism. If you lose muscle mass, your metabolism will slow down. That’s how the yo-yo cycle begins — and that’s one reason why some diets don’t work, she explains.

“That’s why we advocate losing weight slowly and gradually, so you’re losing one to two pounds per week,” Zelman says. “You’re eating more food than diets allow, but you’re tapping into stored fat more efficiently.”

Does the weight loss program involve eating just one food — or eliminating whole food groups?

“That’s crazy,” says Zelman. “No one can stay on those diets very long.”

Sure, you can do it in the short term — with some success, she says. “If you’re eating all the cabbage or meat you want, you go into a state of ketosis. This causes your appetite to go away, so ultimately you don’t eat as much — probably you’re down to a 1,000-calorie diet. Anyone on a 1,000-calorie diet will lose weight.

“Even the strangest diets will pull weight off you, because the basic formula to weight loss is burning more calories than you eat.”

Does the program help you change long-term eating habits?

If not, you’ll just get caught up in a never-ending lose-gain cycle — better known as “yo-yo” dieting.

Most diets are short-term fixes for a long-term problem, says Zelman. “People who get slim and stay that way have changed their eating habits and attitudes toward food.”

Does it involve exercise?

If it doesn’t, you will gain the weight back. “Research shows that individuals who exercise on a regular basis have much greater success at losing weight and keeping it off … Exercise is critical to weight loss success,” Cedric Bryant, PhD, chief exercise physiologist for the American Council on Exercise, tells WebMD.

You need an hour of aerobic exercise — at least five times per week — if you seriously want to lose weight, says Bryant. “That doesn’t need to be in one concentrated dose, because calorie-burning effects accumulate over time.”

Also, you need strength training two times a week to build muscle. Lifting weights or working with rubber tubes helps maintain and can also increase the level of lean body mass — which helps your metabolism burn calories.

“Two-thirds of the calories a person burns over the course of a day are from resting metabolism,” says Bryant. “If you’re on a restricted diet (decreasing calories and nutrients) and not doing resistance training (to build muscle), it’s not uncommon to see resting metabolism decrease — so you won’t lose weight.”

Are supplements, creams, or patches involved?

If so, forget it. “It’s the old saying, ‘if it sounds too good to be true, it is.’ Why would we have an obesity epidemic if it was as easy as popping a pill?” says Zelman.

“By and large, products are not capable of helping you lose weight. Ephedra has been banned from the market, and it was the major ingredient of weight-loss supplements.” That should send a big message: These things are either not healthy or do not work, she says.

Products that block absorption of fat, such as Xenical or Orlistat, may have only minor weight-loss potential — and they’re expensive, says Zelman.

The problem: “These are all Band-Aid approaches to the problem. Even though it’s not sexy, and not any fun, people know what they need to do. You don’t need to be a rocket scientist to know that eating sweets, eating constantly, drinking alcohol, eating fast food are all the things that add extra calories.”

Is there sound research behind the weight-loss program?

“Not all studies are created equal, and there are plenty sponsored by companies to get the answers they want. So a fair amount of skepticism is in order,” says Zelman.

If the study involves small numbers of people the the results are less meaningful. Use caution when making any decisions based on the finding. Also, if claims only involve anecdotes and testimonials, beware.

Is the weight-loss program compatible with your lifestyle?

“If it’s asking you to eat every three hours, to buy special foods and prepare them specially, it might be more trouble than it’s worth and you won’t do it,” says Zelman.

Does it sound easy?

Diets or supplements that tout “no dieting or exercise needed” or “permanent weight loss, even if you stop using the product,” are bogus, says the FTC. If you rely on supplements or too-strict diets you’re wasting your time, Zelman explains.

Likewise, don’t put much weight in the negative-calorie food diet. The theory there is that when you eat lettuce, celery, and other near-zero calorie foods, your body burns more calories simply digesting them. Give me a break, says Zelman. “You may burn a few calories, but so what?”

Sure, some diets work and they’re healthy, Zelman says. “The Atkins and South Beach diets both have merit,” she says.

Also, “protein and calcium are showing great promise as weight loss enhancers,” she tells WebMD. “But they’re not miracle foods; you still have to eat a low-calorie diet, and you still have to exercise.”

Published Jan. 7, 2004.