(FORTUNE Small Business) – Americans keep getting fatter. in 2001 more than 44 million people were obese, a figure that was up 74% from ten years earlier and is ballooning faster than our collective waistline. While that fact might make public health professionals cringe, it also means a growing market for a small army of diet doctors who are pitching their weight-loss prescriptions--in an attempt to promote what they consider good health, naturally, but also to make money. And getting their message out to the $40 billion weight-loss marketplace has proved to be one part medicine and one part (at least) entrepreneurship.

Controversial cardiologist Robert Atkins started the current diet-doctor craze when he published his high-protein regimen in 1972. Before he died in April, he built an enterprise that brought in more than $100 million a year, selling foods (low-carb cheesecake, anyone?), supplements, and even vacation cruises. Not all the doctors on the following pages hope to emulate Atkins's empire-building ways. But they are all fighting to create successful businesses out of what they each claim is the one true prescription for healthy eating. Who's right? Search us. But here's a look at the health and business philosophies of the entrepreneurial doctors fighting obesity, heart disease, and one another.

SUGARBUSTERS

LUIS BALART, MD; MORRISON BETHEA, MD; SAM ANDREWS, MD; H. LEIGHTON STEWARD (Not Shown)

COMPANY: SugarBusters LLC. LOCATION: New Orleans. ESTABLISHED: 1995. FORMULA: Cut down on sugar and other high-glycemic carbohydrates. PRODUCTS: Six books; a line of SugarBusters foods, from bread to salad dressing. 2002 SALES: Nearly $1 million. BREAKTHROUGH: Ballantine Books picked up its self-published diet book in 1997 after it became a local bestseller. BUSINESS PHILOSOPHY: Branding is everything. SugarBusters' name was chosen because it's easy to remember, like the company logo--a slashed-out sugar cube. "It kind of stuck," says Bethea.

THE SCHWARZBEIN PRINCIPLE

DIANA SCHWARZBEIN, MD

COMPANY: Di & Mo Enterprises Inc. LOCATION: Santa Barbara. ESTABLISHED: 2000. FORMULA: Don't count calories. Fix your metabolism instead. Eat a balance of protein, fat, and real carbohydrates; cut stress; quit toxic habits; lift weights; and take hormones to correct imbalances if necessary. PRODUCTS: Four books, metabolic tests, and a strength-training video in which she leads the exercise regimen. "I walk the walk," Schwarzbein says. 2002 SALES: Started website in 2003; expects to bring in nearly $200,000 this year. BREAKTHROUGH: A literary agent bought Schwarzbein's self-published book, The Schwarzbein Principle, at a pharmacy in Ojai, Calif., lost 100 pounds, and helped her win a contract in 1998 with Health Communications Inc. BUSINESS PHILOSOPHY: Lets customers drive her business, rather than vice versa. Schwarzbein began offering her books and training video only after her patients requested them. "I've never thought of myself as an entrepreneur," says Schwarzbein, who doesn't advertise or market her diet. "I don't try to make it sexy. I've been approached by a lot of people who could have made me rich very quickly. I'm not in it for the money."

EAT RIGHT 4 YOUR TYPE

PETER D'ADAMO, ND

COMPANY: North American Pharmacal Inc. LOCATION: Norwalk, Conn. ESTABLISHED: 1996. FORMULA: Slim down and get healthier by eating foods that are best for your blood type: a low-protein, high-carbohydrate diet for type A's; high-protein, low-carbohydrate for types B and O. "In America, we have two separate camps--Dean Ornish and Pritikin on one side, vs. the Zone and Atkins-type diets--claiming their system works well on everybody," says D'Adamo. "There aren't any good or bad diets, only good or bad fits." PRODUCTS: Nine books, dietary supplements and beverages, blood-testing kits, and educational materials. His company also conducts conferences and training sessions for physicians who want to use the diet in their practice. 2002 SALES: Won't say. BREAKTHROUGH: A 1994 interview in Details magazine led to a deal with Penguin Putnam. BUSINESS PHILOSOPHY: Think small. "I don't think we could possibly compare to Dr. Atkins's operation. We produce unique, esoteric, avant-garde things I want to have in my practice. The company is a vehicle to make blood-type-specific products I can't get anywhere else. It really isn't our focus to produce a trillion-dollar bestseller."

PROTEIN POWER

MICHAEL AND MARY DAN EADES, MDs

COMPANY: Advanced Metabolics. LOCATION: Incline Village, Nev. established: 2001. FORMULA: Eat steaks, cheese, and eggs and still lose weight. Build your meals around protein, fruits and vegetables, and healthy fats. PRODUCTS: Six books in print, three Slow Burn exercise videos, subscription newsletter, Pentabosol weight-loss supplements. 2002 SALES: $27 million. BREAKTHROUGH: Created its own infomercial in 2002. "You can start with very little money, and if you have a successful infomercial, within a year it creates demand out there so you can get your product onto retail shelves," says Michael Eades. Following the commercial's success, the Eadeses have begun negotiating to get their goods in stores. BUSINESS PHILOSOPHY: Trust in your personality to set you apart from the competition. "Our big problem has been trying to stand out in a crowded field," Michael says. "I think we can do it. We come across in our infomercial as being credible and sincere, which we are. We've got the clinical data behind us."

THE ZONE

BARRY SEARS, PH.D.

COMPANY: Sears Labs. LOCATION: Danvers, Mass. ESTABLISHED: 1999. FORMULA: Get rid of your gut and avoid heart disease by eating five times a day. Stick to a diet that's 40% carbohydrates, 30% fat, and 30% protein. Avoid refined sugar and starchy foods like bread and rice. PRODUCTS: Sears has released nine Zone books, plus insulin-control bars, fish oil supplements, and skin-care products under the Dr. Sears brand. (The popular ZonePerfect bars are not part of his business.) 2002 SALES: $5.5 million. BREAKTHROUGH: He persuaded doctors to test his fish oil supplement on cardiovascular patients in 1984. Seeing patients' bloodwork improve, they began ordering it from his startup, BioSyn. BUSINESS PHILOSOPHY: Make your product a luxury. "We basically sell the Mercedes of food products. They're not for everyone--they're definitely not mass-market items. The one that constitutes the vast bulk of our sales is a new grade of fish oil that has profound anti-inflammatory actions. It shows that the Internet, coupled with a good product, can actually make money."

EAT MORE, WEIGH LESS

DEAN ORNISH, MD

COMPANY: Lifestyle Advantage. LOCATION: Sausalito, Calif. ESTABLISHED: 2000. FORMULA: Lose weight and improve your health by increasing your consumption of fruits, vegetables, whole grains, and legumes and reducing your intake of fats and simple carbohydrates. PRODUCTS: Five books and cassettes. Trains hospitals and conducts retreats to teach patients how to follow his Lifestyle Advantage program to reverse heart disease. Some of the proceeds from his program go to fund his nonprofit research institute. 2002 SALES: Won't say. BREAKTHROUGH: In 1990, published findings in the medical journal The Lancet that showed his diet could reverse heart disease. BUSINESS PHILOSOPHY: "I'm not a diet doctor, I'm a medical researcher," says Ornish, whose Lifestyle Advantage did not show a profit last year. "That's what I've spent 26 years doing. It would be much more profitable to tell people what they want to hear. My approach has always been to tell people what's true."