There's one that identifies three body types, based on the autonomic nervous system. Another book lists three color-coded types, drawing from traditional Indian medicine. One specifies four types, determined by insufficient brain chemicals. Another singles out six types, growing out of a blend of East and West. Yet another gets up to 25 variations, determined by which gland, organ or body system is dominant.

What I can't quite tell is which has become more precise — the science or the marketing.

Maybe it's both, of course, or neither. Perhaps in a few years one of these systems will be the norm, or they'll all have gone the way of the grapefruit diet. In the meantime, I'm not sure how anyone decides to pick one of these over another.

In "The Metabolic Typing Diet" ($14.95, Broadway Books), William Wolcott says the two branches of the autonomic nervous system — sympathetic and parasympathetic — result in unique ways individuals process foods and use nutrients, which calls for three diet types: protein, carbo and mixed.

Fitness news you can use Cooking seafood If you're committed to eating more fish but are running out of ways to prepare it, two new cookbooks with more than 100 recipes each might help: "Seafood Twice a Week" by Evie Hansen and Cindy Snyder and "Seafood Grilling Twice a Week" by Hansen ($14.95 each; National Seafood Educators). The first has 146 and the second 126 recipes. Supplement guides Tempted by diet drugs and supplements? "The Diet Pill Guide" by Deborah Mitchell and David Charles Dodson ($12.95, St. Martin's Press) provides a rundown of names, types, how sold, research, claims, dosage, side effects and precautions for prescription drugs and over-the-counter products, both generic and brand name. The fourth edition of "Sports Supplement Review" by Vince Andrich ($4.95, Mile High Publishing) has more than 300 pages of details on substances favored by many athletes and bodybuilders; it's put out by EAS, which makes nutrition bars, drinks and supplements. Name change Beginning with the March/April issue, New Age Journal is changing its name to Body & Soul.

"Eat Your Colors" by Marcia Zimmerman ($14, Owl Books) draws from principles of Ayurvedic medicine to identify three body types, color-coded to correspond to three eating plans — Red, Yellow and Green — intended to "access the healing power of nutraceuticals" (foods with health benefits).

"Turn Off The Hunger Switch" by Paul Rivas ($24, Prentice Hall Press) contends that weight gain is from hunger created by faulty brain-chemistry messages. Rivas, a Maryland M.D. who specializes in treating obesity, identifies four types of people: those with deficiencies in serotonin, norepinephrine or dopamine or those with a carbohydrate sensitivity. Recommendations include over-the-counter supplements (ma huang, guarana, SAMe) and prescription medications (phentermine, Wellbutrin, Prozac).

"Your Body, Your Diet" by Elizabeth Dane ($25.95, Ballantine Books) claims to be the first nutrition and lifestyle guide to unite Eastern and Western philosophy to create personalized diet and exercise programs. It identifies six major "Meta-types," and for each addresses food combinations, acid/alkaline balance, vitamins, minerals, amino acids, essential oils, Bach flower remedies, acupressure points and exercise programs.

"Different Bodies, Different Diets" by Carolyn Mein ($25, ReganBooks) introduces 25 body types, differentiated by dominant gland, organ or system. Mein, a California chiropractor, says these types determine certain physical characteristics and psychological traits and have corresponding ideal weights, diets and exercises.

Some new titles present more conventional approaches and include specific plans to follow.

"Combat Fat!" by Andrew Flach ($23.95, Hatherleigh Press) features an eight-week fat-loss diet and exercise program that emphasizes monitoring body fat (skinfold calipers come with the book) rather than weight. The diet, based on federal guidelines released in 2000, calls for 12 to 20 percent protein, 55 to 65 percent carbohydrates and 25 to 30 percent fat.

"The Take Control Diet" ($23.95, Random House) by Ian Smith, medical correspondent for NBC's The Today Show, has a 30-day menu and exercise program, with goals based on the Body Mass Index.

"Get a Real Food Life" by Janine Whiteson ($24.95, Rodale) offers an eight-week approach using self-diagnostic quizzes and a food journal to increase awareness of eating patterns.

Some effective changes in eating patterns may have less to do with the type of diet than with an individual's circumstances or a particular trigger: a health scare, upcoming class reunion, pending swimsuit season.

And sometimes it might be getting advice that just rings true, such as one gem in "The Okinawa Program" by Bradley Willcox, D. Craig Willcox and Makoto Suzuki ($24.95, Clarkson Potter). The book is based on a 25-year study which found that, compared with Americans, the people of these Japanese islands age relatively slowly, and are at 80 percent less risk for heart disease, breast cancer and prostate cancer. Their diet is plant-based, high in complex carbohydrates, low in calories, with moderate fat and protein.

But the Okinawan lesson I'll probably retain the longest is a cultural habit called hara hachi bu. It means, simply, to eat until you are 80 percent full. And then stop.

Molly Martin is assistant editor of Pacific Northwest magazine. Boo Davis is a Seattle Times news artist.

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