TOPICS > Health

Diets Evaluated

January 11, 2001 at 12:00 AM EDT


RAY SUAREZ: It’s an American obsession, perhaps even a pastime of sorts: Dieting; trying to shed fat, getting rid of those extra pounds. As many as 50 million Americans try going on a diet each year, spending an estimated $33 billion on diet books and programs. Overall, according to government studies, about 60% of adult Americans are considered overweight. One in four ranks as obese. And it’s not just an issue of appearances.

KEITH- THOMAS AYOOB, Albert Einstein College of Medicine: Six out of the ten leading causes of death in this country can be traced to diet. We know that being overweight increases risk for heart disease, hypertension, diabetes, and all sorts of other chronic health problems.

RAY SUAREZ: In fact, the government estimates that nearly 280,000 deaths a year are caused by illnesses related to the effects of obesity. Exercise is one required solution. But what about all those diet plans? There are several popular approaches. One is a high-protein diet popularized by Dr. Robert Atkins that allows one to eat plenty of red meat, eggs, and cheese. Under that plan, one eats far fewer sugars and far less carbohydrates, like bread and pasta. According to Atkins, those kinds of carbohydrates increase the body’s production of insulin. That insulin, in turn, converts sugars from carbohydrates into body fat.

DR. ROBERT ATKINS: You can take in more calories than you can on other diets, and still lose weight. You can go to restaurants, order from the best of the main courses. It will correct diabetes, hypertension, most of the risk factors of heart disease.

RAY SUAREZ: Another popular plan is one favored by Dr. Dean Ornish. That diet calls for much less fat– about 15% of a day’s given calories– more carbohydrates, and less protein.

DR. DEAN ORNISH: Fat has more than twice as many calories per gram as a protein and carbohydrates. So when you eat less fat, you’re eating fewer calories without having to eat less food.

RAY SUAREZ: To help consumers navigate through the maze of choices, the Department of Agriculture has just completed a review of medical studies evaluating diets. At a public meeting today, the agency laid out its findings. Among the main findings: The most important way to lose weight is still to consume fewer calories, about 1,500 daily. More traditional diets that call for less fat and protein, and more vegetables and carbohydrates are still the best. While many diets may help shed pounds quickly, too many do not help keep the pounds off for good. The report says it’s more important to try to keep the weight off for more than a year.

RAY SUAREZ: The report emphasized that longer-term studies remain necessary. Joining me now is the woman who oversaw the report, Dr. Eileen Kennedy. She is Undersecretary for Research, Education, and Economics at the Agriculture Department.
Well, Dr. Kennedy, eat fewer calories, I mean…

DR. EILEEN KENNEDY: Sounds like we’ve known that for a long time.

RAY SUAREZ: So what’s the big finding?

DR. EILEEN KENNEDY: I think there is a lot of confusion. And if you look at why we did the study, about a year ago we had some of the major diet book authors in the Department debating, the great nutrition debate– some of the people that were just on your show earlier. And while there was enormous disagreement on a range of issues, the one issue where there was overwhelming consensus is we need more research. So we immediately started with our phase one, which has just ended: The report you’re talking about, to look at what do we really know. We’re not starting with a blank piece of paper. We do know a lot about the effectiveness of various diets. What we knew less about, because so much of this earlier work had been done in medical clinical studies, we knew less about what happens to people who use what I call self-help diet books, and so we took the major kinds of diets, and they really fall into three categories: The low carbohydrate, high fat, similar to Dr. Atkins’ book; the very low fat, high carbohydrate, which is Dr. Ornish; and the moderate fat, high carbohydrate, which prototypes a lot of our commercial diet plans like Weight Watchers and Jenny Craig, and looked at what you can say about overall effects on health, not just weight loss.

RAY SUAREZ: And when I was reading the report, the conclusion that any diet can produce short-term weight loss sort of jumped out at me. What else should we be thinking about, if any diet will produce short-term weight loss? What else do you have to think about before you make a decision?

DR. EILEEN KENNEDY: I think to clarify that point a little, any diet can produce short-term weight loss if you reduce calories. And what we see, contrary to some claims about these diets that… for any of the kinds I’ve just talked about, people who lose weight in the short-term on any of these diets do so because they’ve reduced calories. So these claims that you can eat as much as you want and still lose weight, there is no scientific literature that substantiates that point. And we today presented analyses on 10,000 people, and what we find is if you eat all you want, you put on weight. So in addition to cutting back on calories, you really do need to think about overall lifestyle changes. Our report talks about individuals who keep weight off long-term, and this research is by no means complete. But where we look at the documentation that’s there, individuals who keep weight off long term, and one definition of that is people who have lost more than 30 pounds and kept it off for a year — those individuals, by and large, are number one, keeping calories relatively low, eating a moderate-fat diet, again the sort of Weight Watchers food guide pyramid kind of diet. That’s one part of – that’s what they’re eating. They’re also regularly exercising. This is not surprising – regularly exercising — and for these, what I call weight maintainers, it’s not 30 minutes three or four times a week. It’s actually closer to an hour most days of the week. There are also some other markers of their overall healthy lifestyle.

RAY SUAREZ: It’s really about changing your lifestyle, not just following a guide in a book?

DR. EILEEN KENNEDY: Changing your lifestyle. Right.

RAY SUAREZ: Let’s talk about diets harder or easier to follow. Ones that were very demanding– did you find short-term compliance, but then that people would sort of fall off the wagon over a period of time?

DR. EILEEN KENNEDY: It depends if you’re talking about the average free-living individual. You, and I in our everyday lives, will find– and in fact we see this in our research– find it easier to stay on a moderate-fat, high- carbohydrate diet. From the point of view of overall health, the very low-fat diets, the Dr. Ornish diets, can be very helpful, but we don’t find a lot of people long-term staying on them because you have to think about meals you’re preparing. The Dr. Ornish diet in particular has virtually no animal products, no meat, no milk. That’s hard for people to follow. If you look at the low-carbohydrate diets, the Dr. Atkins diet, the meal patterns are what a lot of people describe to us as very bizarre. Since you’re consuming virtually no grains, no fruits, no vegetables, you get up in the morning to have breakfast and you’re having a hamburger. That’s not something that long-term a lot of people find very easy to do.

RAY SUAREZ: Some of the criticisms contained in the report have already been answered by some of the diet doctors who are mentioned in them questioning the methodology, saying that this was just a survey of the literature and not a longitudinal study of real people; some saying, well, if they say that more research is needed– boy, do we agree. What do you do next?

DR. EILEEN KENNEDY: Well, what we do next is we’re doing exactly that. We’re actually doing the longitudinal, forward-looking studies. We’re going to have what is considered the topnotch scientific protocols; we will randomly assign individuals to either a low-carbohydrate diet, a very low-fat or moderate-fat diet, and look not, not simply at short-term weight loss but follow them long term, and long term being a minimum of a year, and not simply look at only weight loss, but look at other indicators of overall health like bone health, heart health, what’s happening to cholesterol levels, what’s happening to functional fitness. And I think only by doing these rigorous random assignment studies long term, will we have some of the answers to questions that are being asked about these diets.

RAY SUAREZ: And will you be able to test the science? We heard both Dr. Atkins and Dr. Ornish making claims about the effects of their diets. Can you test that?

DR. EILEEN KENNEDY: Oh, absolutely. We’ll have agreed-upon scientific protocols following what I call treatment individuals, individuals on the diet, as well as comparison individuals. Dr. Ornish has actually published long- term studies, one- and five-year studies. The problem I have with a lot of the low-carbohydrate books that are out, an Atkins kind of diet: Despite the fact that they’ve been around since the 1960s and 1970s, there is virtually no information that, long-term, individuals can maintain weight loss on those diets. We want to look at that.

RAY SUAREZ: So the short-term recipe for people who want to take off a couple of pounds this year?

DR. EILEEN KENNEDY: Well, the problem is you don’t want to take it off and not keep it off, so make modifications in your overall eating patterns and lifestyles that can be sustained. And, you know, there are simple things you can do. Not any one activity that I’m going to recommend will necessarily suit everybody. It’s not a one size fits all. But if you can move away from your dinner plate still a little bit hungry, if you can, rather than having desserts that are high fat, try to move in the direction of more fruits for dessert. Changing from whole milk to skim milk – there are a whole series — there are 99 recommendations I can make. And what the individual has to do is think “what fits for me?”

RAY SUAREZ: Dr. Kennedy, thanks a lot.

DR. EILEEN KENNEDY: It has been delightful. Thank you.