There are many theories about how to thin down a fattening America. Dr. Marion Nestle, Chair of the Department of Nutrition and Food Studies at New York University, has some pretty dull advice for us on this count: Eat less, and eat well. Though it sounds simple, and even smug, Nestle acknowledges just how hard it can be to follow this advice. "Everybody knows you're supposed to 'eat your veggies,' and what could be less interesting?" says Dr. Nestle. "But it's actually very hard to do."

In her recently published book, Food Politics: How the Food Industry Influences Nutrition and Health, Nestle contends that the influence of the food industry in popular media, nutritional research, and policy-making, is making it increasingly difficult for Americans to make good choices about food.

Below, she talks about the relationship between food industry tactics, and the ever-expanding American waistband.

In the news, we read that carbohydrates are "good" one day, then "bad" the next. Is good nutrition really this confusing?
No, it's really very simple. Eat less, move more, eat more fruits and vegetables and don't smoke. If you do those things, you've taken care of 95% of what you need to do.

What's confusing is when you start looking at individual nutrients-proteins, fats, carbohydrates, vitamins, minerals, fiber, antioxidants-There are about 50 to 100 different components in the diet that have some effect on health. When you single them out and study them individually, you're going to get one result or another. And it's very easy for people to find studies to support their point of view about good nutrition.

When you look at dietary patterns, the advice never changes and hasn't changed in 50 years. And that's to eat a diet that's balanced in calories where a substantial proportion of those calories come from fruit and vegetables.

Then why does the news focus so much on single-nutrient studies?
It's more fun! It's a lot more fun to read about a single nutrient. We like simple solutions to complicated problems. It's much easier to think, "If I just eat a low-fat diet or don't eat any carbohydrates, my weight problems will be solved," than to think "I really need to build some activity into my life. I need to try to eat less often and smaller portions." That kind of consciousness about diet is uncomfortable for practically everybody.

When did portions start growing, and what role does larger portions play in the fattening of America?
In about the mid-80s, companies began introducing larger portions than had been seen before. That's when muffins went from one or two ounces to six or eight ounces, and bagels went from two ounces to six ounces.

Now people are eating more calories then they're expending in activity. To maintain weight, you have to balance the calories and to lose weight, you have to eat fewer calories than you're expending. So you've got two choices. You can either adjust intake or you can adjust expenditure or you can do both. Large portions alone could account for the rise in levels of obesity across the population.

Why would food companies want to offer larger portions?
Because the food itself doesn't cost very much. In many ways the government subsidizes the production of the basic components of fast food and soft drinks, like corn, soy beans, wheat, and sugar. So they're artificially less expensive. Companies can charge just enough more for a larger portion to make a greater profit, without spending much more in food production. And most people feel stupid buying a smaller portion because the larger one is evidently a much better bargain.

How much food does the food industry actually create per day, per capita, compared to the number of calories that are recommended we eat?
According to the Department of Agriculture, our food supply provides an average of 3,800 calories every single day for every man, woman and child in the country. That figure includes what's produced in the United States plus imports, less exports. And it's roughly twice what the average person needs.

So there's this tremendous surplus of food. And what that does is make the industry extremely competitive. And it becomes the job of the industry to try to get people either to eat their product instead of someone else's, or to get people to eat more in general.

Isn't the food industry just doing its job, which is to sell food?
Sure, their job is to sell food. Where I think it crosses an ethical line is when the industry directly markets to children. Companies are marketing foods to children that are high profit and not particularly healthful. The adult population has free will and is able to think critically about food and health. But children don't have the same level of critical thinking. The advertising and marketing designed for kids is not about the taste or health value of a product. It's designed to make kids think that one or another product is "cool." And we're seeing kids get fatter and fatter and develop Type 2 diabetes in numbers we've never seen before.

A few years ago, Consumer Reports did a survey of food companies in schools, and they were able to identify more than 50 different food companies and products. Every trade association, product and soft drink company-anything that you could think of, it was in school.

Can you give us an example of the food industry's influence in the schools?
They produce teaching materials, give away product samples and advertise on score-boards. They advertise on required television programs that students watch. They contract with school districts for exclusive use of one or another soft drink product in the school, which forces the school to install vending machines that compete with school lunches. The ways in which food companies are present in school are limited only by imagination.

The food industry spends about $30 billion a year on advertising and marketing. Something in the order of $10-15 billion is spent for marketing specifically to children. It's a terrific market, not so much because kids have a lot of money themselves-although in aggregate they do-but because they strongly influence their parents' purchases.

Does the food industry get involved in nutritional science and research?
Food companies try to make sure that there aren't any ideas out in the world that there might be something unhealthful about what they're selling. They do it in an especially nice way. They sponsor research, meetings, travel and journals. They provide food and product for events. They cooperate with food and nutrition professionals. And of course, food and nutrition professionals seek out food company support because they need the money.

Do you feel that the company's involvement in research sometimes biases the research results?
If you talk to researchers who are doing this kind of research, on the record they will tell you that the sponsoring company had no influence whatsoever on the results of the research. If you talk to them off the record, you sometimes get a different story.

The biases can be very subtle. There have, however, been some documented cases-not all, by any means-where companies have asked to see the research data in advance and have edited the data. And if they didn't like it, they delayed publication or prevented the authors from publishing. So in some cases it gets quite heavy-handed. In others, it's much more subtle.

In the mid-80's you worked for the Public Health Service to create the Surgeon General's Report on Nutrition and Health. What were the results of this report?
Well, this was to be a comprehensive report on the relationship of factors in the diet to chronic disease risk. It was the first federal report on diet and prevention of the kinds of diseases that are now leading causes of death and disability-heart disease, cancer, diabetes and so forth. But it was clear from day one that the report was not going to be able to say "eat less" of any specific food commodity because the makers of that food or the producers of that food would complain. The report would never, for instance, say "eat less meat," no matter what the research showed -- because the meat industry would complain to the Department of Agriculture. And that would be the end of it. The report would never come out.

There are cattlemen in every state. Every state has two senators. Cattlemen make campaign contributions. And these very, very large corporations have a great deal of clout with Congress.

So how did you write the report?
Well, instead of saying "eat less meat" it said "choose lean meat." That's a euphemism. Instead of saying "limit intake of added sugar," it says "choose a diet that's moderate in sugar." That's a euphemism.

So essentially the language is asking us to eat, rather than not eat, or eat less?
Yes. Dietary recommendations are always stated positively. They never tell you not to do something. They always tell you to do something. For example, what is "moderate?" It's anything that's smaller than what you're already eating, regardless of what size it is. This euphemistic language has played a role in creating extreme confusion among the public about what is healthful.

Aren't we each, finally, responsible for our own health, and controlling our own weight?
Of course. But you're not making choices in a vacuum. We live in an environment in which food is promoted and in which we are expected to be eating and drinking far more than three meals a day. The question is, how do we change that to make it easier for people to exercise restraint? Many people are just weary of trying to make healthful choices in an environment that is so destructive of those kinds of those kinds of choices. It's not just a matter of will power.