Credentials: Dr. Atkins has a string of weight-loss books to his credit, starting with his 1972 blockbuster, Dr. Atkins' Diet Revolution.
Promise: You can eat as many or even more calories than you normally do and still lose pounds and inches. The one requirement: You have to cut back drastically on carbohydrates to force your body to burn stored fat.
Program: There are four phases: The 14-day Induction diet is designed to "correct" your unbalanced metabolism. You're allowed to feast on unlimited fat and protein (butter, oil, red meat, poultry, fish, eggs, cheese), but daily carbohydrate intake is restricted to a scant 15 to 20 grams (about three cups of salad vegetables, such as lettuce, celery, cucumber, and alfalfa sprouts). The next stage, Ongoing Weight Loss, allows 15 to 40 grams of carbohydrates a day. (A useful carb-gram counter lists about 200 foods.) As you near your ideal weight, you head into Pre-Maintenance, slowly adding one to three weekly servings of high-carbohydrate foods, such as a peach (10 grams), a slice of whole-wheat bread (14 grams), or a cup of plain yogurt (13 grams). Once you reach your goal, you maintain that target weight by eating 40 to 60 carb grams per day.
Pitfalls: Pigging out on omelets, bacon cheeseburgers, or one of the book's fat-laden recipes like Swiss Snack (deep-fried cheese wrapped in bacon) may sound like a dream diet until you start craving toast with that omelet or a bun with the burger. Without enough carbohydrates, the body doesn't burn fat efficiently, and substances called ketones accumulate in the blood. This condition, called ketosis, may initially make dieting easier (due to rapid water loss and a reduced appetite), but it is not the "nirvana" that Dr. Atkins claims. Ketosis is often accompanied by nausea, headaches, fatigue, and bad breath, and may exacerbate existing medical problems, such as gout and kidney disease. Likewise, a diet rich in fat increases the risk of heart disease and cancer.
Credentials: Sears, a biochemist, is the author of 1995's megahit diet book, The Zone.
Promise: Within one to two weeks of Zoning, Sears claims that you will improve your mental and physical performance, rapidly shed excess body fat, and never be hungry between meals. You'll also protect yourself against heart disease, diabetes, premenstrual syndrome, depression, and cancer, as well as slow down the aging process.
Program: The key to keeping yourself in the Zone is planning every meal so that it contains the appropriate ratio of proteins to carbohydrates. Complicated formulas and charts allow Zoners to determine their personal protein requirements. This quota must be divided so that no single meal exceeds 35 protein grams (equal to a five-ounce chicken breast). Zoners are encouraged to choose protein foods low in saturated fat, like turkey breast and fat-free cheese. Zone-friendly fat sources are high in monounsaturates (olive or peanut oil). "Unfavorable" carbohydrates (grains, starchy vegetables, fruit juices, pasta, bread) are grudgingly allowed, but portion sizes are tiny (one-quarter cup of cooked pasta, one-square-inch of corn bread, one-eighth cup of baked beans). Our analysis of three daily sample menus for women averaged about 1,300 calories.
Pluses: Emphasis is on lean protein sources, keeping artery-clogging, saturated fat to a minimum.
Pitfalls: Once you reach your ideal body weight by really slashing calories, you generally need to increase calories to maintain it otherwise you'll keep losing weight to unhealthy levels. But with this diet, your only option is to add more fat, since adding extra protein or carbohydrates will cause an imbalance of the Zone's protein/carb ratio. While no food is truly forbidden, choices, combinations, and portions are sometimes unusual and hard to live by. A serving of peanut butter is a half teaspoon, and a sample dinner suggests a half cup of cranberries (uncooked and unsweetened) as a side dish. Snack suggestions include two hard-boiled egg whites, half an apple, and three almonds, or if you prefer, a glass of red wine with a couple of spoonfuls of cottage cheese. Bon appétit!
GHI Recommendation: This complex, restrictive plan's claims for achieving SuperHealth are not supported by scientific evidence. Follow the plan exactly, and you will lose weight but only because it cuts calories. If you decide to enter the Zone, take multivitamin/mineral and calcium supplements with you.
Eat Right 4 Your Type By Peter J. D'Adamo, N.D. (G.P. Putnam's Sons, 1996)
Credentials: A licensed naturopath (trained in natural healing) with a private practice in Connecticut.
Promise: D'Adamo believes that by using the genetic characteristics of your blood type as a guidepost for eating and living, you'll naturally reach your ideal weight and slow the aging process. In addition, you'll protect yourself against common infections, cancer, heart disease, diabetes, and liver failure.
Program: According to this theory, Type Os, whose genetic ancestors were hunters and gatherers, do best on a diet that's high in animal protein and low in carbohydrates with no wheat products. Type As, whose predecessors were farmers, should be vegetarians, avoiding most meats and dairy products. Type Bs, who trace their forefathers to nomads, should eat red meat, fish, and most dairy foods, but avoid chicken, shellfish, and wheat. Type ABs should follow a combination of diets for Types A and B.
Pluses: Lean sources of animal products are emphasized. Several servings of fruits and vegetables are recommended daily for all diets.
Pitfalls: Our attempts to estimate the caloric level of the sample daily meals using the lower-calorie alternatives showed that calories could vary widely from day to day. For example, one daily meal plan for Type AB was about 1,000 calories, another added up to more than 2,000. Sample meal plans often include unusual and hard-to-find foods, such as Ezekiel bread, quinoa flour, spelt lasagna noodles, and chestnut flour. Eating out could prove difficult, and preparing meals when several family members have different blood types poses a real challenge.
GHI Recommendation: There is very little scientific evidence to back up D'Adamo's unusual theories about diet and blood type. He refers to his research throughout the book but does not list a single study he has published in a scientific journal. With careful planning one could eat a reasonably nutritious diet on this plan. And with so many foods off limits, the diet is likely to take off weight. But when you balance the many restrictions and the inconvenience against the lack of proven benefits, there's little value in following this strange regimen.
Credentials: A registered dietitian whose previous book, Thin for Life, won a 1995 National Health Information Award.
Promise: Learn how to lose weight and keep it off without suffering or denying yourself.
Program: The 21-Day Weight-Loss Plan consists of 21 fat gram- and calorie-counted breakfasts, lunches, and dinners, along with snack and dessert ideas. The daily total for women (three meals plus a 100-calorie snack) averages around 1,300 calories with less than 20 percent coming from fat. You're encouraged to plan your own meals, and Fletcher shares tips from people who have lost at least 20 pounds and kept it off for three years or more.
Pluses: Meals are easy to prepare, nutritious, and can be mixed and matched. You can pick and choose from an abundance of tips and strategies that best suit your lifestyle and food preferences.
Can a person eat unlimited calories, and still lose weight, as long as they severely restrict carbohydrates?
No, they cannot. The basis of ketogenic diets, such as the Atkins Diet, is a severe restriction of carbohydrate calories, which simply causes a net reduction in total calories. Since carbohydrate calories are limited, intake of fat usually increases. This high fat diet causes ketosis (increased blood ketones from fat breakdown) which suppresses hunger, and thus contributes to caloric restriction.
Low carbohydrate diets are also characterized by initial rapid weight loss, primarily due to excessive water loss. A decreased carbohydrate intake causes liver and muscle glycogen depletion, which causes a large loss of water, since about three parts of water are stored with one part of glycogen. Also, restricting carbohydrate intake reduces the kidney's ability to concentrate urine, leading to an increased excretion of sodium. All these factors combine to cause a powerful but temporary diuresis.
Dieters cherish this rapid initial weight loss and assume it represents fat loss. Actually, their body fat stores are virtually untouched. And, as the body adjusts for the water deficit, the weight loss slows or ceases. The dieter often becomes frustrated and abandons the diet. Individuals who do stick with it may lose weight due to the caloric restriction mentioned above.
Complications associated with low carbohydrate, high protein diets include ketosis, dehydration, electrolyte loss, calcium depletion, weakness (due to inadequate dietary carbohydrate), nausea (due to ketosis), and possibly kidney problems. Vitamin and mineral deficiencies are other problems in such unbalanced crash diet regimens. Even Dr. Atkins, the author of both old and new versions of Diet Revolution, admits that his diet doesn't supply enough vitamin and minerals and recommends that people take supplements.
Gout is another potential side effect, since the uric acid in the blood increases as the uric acid competes with ketones for excretion. This higher blood uric acid level can also increase the risk of kidney failure. Dr. Atkins does warn that people with kidney problems shouldn't follow his diet, but he doesn't mention that the diet might produce these disorders.
Lastly, the risk of coronary heart disease may be higher in susceptible persons who stay on the diet a long time, due to increased consumption of foods high in saturated fat and cholesterol.