Four years ago, a group of researchers at the University of Michigan conducted a survey of hospitals and found that 4 out of 10 had fast food restaurants on their premises. Today, I'm afraid, that number can only have gone up - judging by how often I and my colleagues cringe at the sight of new burger and pizza places in medical centers.

With the obesity epidemic in America getting more attention every day, nutrition experts tell us we exercise too little, eat too much and eat too much of the wrong kinds of food. What are the wrong kinds of food? We are constantly told to cut back on fat and sugar, but to my mind the greater problem is the processed food that, over the past 50 years, has increasingly displaced whole, natural food in the American diet. The proliferation of fast food is a glaring example of that change.

Modern food technology has transformed slow-digesting grains into snack foods made of pulverized, refined starches that, once eaten, quickly raise blood sugar, promoting insulin resistance and weight gain in genetically susceptible individuals - most of us, unfortunately. We have invented high-fructose corn syrup, a cheap sweetener that is ubiquitous in soft drinks and most of the sweetened products in supermarkets and convenience stores. And we have processed oil-rich seeds into chemically altered fats that can promote inflammation, heart disease and cancer.

All three of these products abound in fast food, one of America's worst contributions to world culture and cuisine. As the movie "Super Size Me" pointed out, the increasing availability and popularity of fast food is a major cause of obesity and declining health. How remarkable, then, that our hospitals would house fast food restaurants. Hospital administrators apparently like them as a source of revenue and a draw for employees, visitors and even patients. A year and a half ago, when the head of the Cleveland Clinic bravely tried to get rid of the McDonald's at that hospital, staff members and visitors made it clear they liked having the franchise close by. (McDonald's pointed to the 10 years left on its lease and refused to budge.)

Expelling fast food from hospitals is an obvious step to better health, but suggest it and you run into the same tangle of inertia and apathy that has kept hospitals from serving patients appetizing and wholesome food ‹ and has instead allowed large food service corporations to put profit ahead of quality. I hold my profession responsible for much of the apathy. Nutrition is slighted in medical education. It is considered a "soft" subject akin to home economics, not worthy of the time and attention commanded by important fields like biochemistry and pharmacology.

We must have nutritionally literate doctors, but getting fast food out of hospitals will also require the kind of grassroots activism that has removed sugary sodas and candy from vending machines in many schools. Doctors should model healthy lifestyles for their patients, and hospitals should be places of inspiration and education as well as centers for the treatment of disease. Fast food has no place in them.

Andrew Weil, the director of the integrative medicine program at the University of Arizona College of Medicine, is the author, most recently, of "Healthy Aging."

© 2006 The New York Times Company