Editor’s Note: Dr. Frank M. Sacks was the lead author of one of the largest and longest studies ever to compare the effectiveness of different kinds of diets on weight loss. His study was published in the Feb. 26, 2009 issue of The New England Journal of Medicine.

Arthritis Today: Can you tell us a little bit about the significance of this weight loss study?

Dr. Sacks: The question of what type of diet that can facilitate weight loss is really old and hotly debated, and there are loads of divergent findings in the scientific literature. In other words, there are some findings that favor a low-fat, high carbohydrate diet, some findings that favor the total opposite kind of diet, and there are often problems with many of those kinds of studies.

What we wanted to do was to really test a big range of dietary fat, carbohydrate and protein intakes in a large number of people, 811, and extend it through two years with continual support, with behavior and nutritional sessions in groups and individually.

And we also wanted to make clear that all the diets we’re testing are healthy to prevent heart disease or to prevent diabetes, and some experts would feature one versus another.

We created a really neutral atmosphere. We didn’t want people to go in with a bias that one diet would work better than another.

The results, in a way, surprised us. We thought that the higher protein diet would be more satiating and lead to better weight loss long run, but we didn’t find that at all. We found that protein content really didn’t matter.

What really counted was people’s engagement in the program. Maintaining their commitment and what diet they were assigned to really didn’t have any influence at all.

Arthritis Today: In your paper, you admit that people had a hard time sticking to the diets that were most different from the way they ate before they started the study.

Dr. Sacks: Yes. That’s one of the problems with one of the more extreme popular diets.

For example, take this very low carbohydrate Atkins Diet. What the Atkins studies show is that after the first couple of months, people don’t get down to those very low carbohydrate levels. If they did initially, they can’t maintain that. We didn’t want to test a very low carbohydrate intake. We wanted to study a very large range of carbs, but the lowest carbs, 35 percent, we thought would be possible to go for. What we found was that over time people kind of gravitated back to what their usual carbohydrate, fat and protein intake was. And all in all, their weight loss didn’t suffer from that. What really counted was their engagement in the program.

Arthritis Today: Let’s talk about engagement. In your results, you point out that the people who lost the most weight were the most engaged. One way you measured that was by how many counseling sessions dieters attended. It seems to suggest then that all of us should kind of give up the idea of going with a radical diet and just portion control and get ourselves into some kind of support group.

Dr. Sacks:  Exactly, the result is actually a real, positive, optimistic result for people. It gives people a wide range of diets they can work with. They can try different things. If they want to try the Atkins diet –the Atkins organization has gradually improved their diet so it is healthier in terms of guidelines for heart disease. As long as it’s a healthy diet and they feel comfortable with it, and can stick with it, then that’s what counts. It’s not so much what particular fat or protein intake you’re eating. It’s what you can maintain, enjoy and keep intake down.

Arthritis Today: Was that a true result? In other words, do you think that people who were more engaged attended the counseling sessions because they were more committed to their goals, or do you think that the counseling itself was what was working?

Dr. Sacks: Oh, the counseling was very important. You know it kept them focused on what the goals are. So if they’re engaged in the program, hopefully they’re not sleeping through the program. You know, the sessions that I attended were pretty lively. I mean, people talked a lot about what they’re doing that’s helpful, problems they’ve had, things to surmount, challenges, and so forth, and people in the groups discussed it. You know there really weren’t too many people sleeping through the groups, and the dieticians were really positive and engaged themselves. Participants loved the dieticians and that was really important. You know, if you’re going to a group, you really have to have good chemistry with the group leaders, the dieticians, the group leaders… so find a group that you like, people that you get along with and keep going.

Arthritis Today: Diet composition didn’t seem to matter when it came to weight loss, but as you were crunching the numbers and analyzing the data, did you find that diet composition did have an effect when it came things like to blood lipids or insulin or glucose? When you have diabetes, people are often counseled to go on a low-carb diet.

Dr. Sacks: Well, we didn’t have diabetics in our study. I mean, nonetheless, for diabetics, the results of the study are certainly applicable with the proviso that they really have to be careful about carbohydrates. You know a diabetic can eat a higher-carb diet but then they really have to pick diets with low-glycemic carbohydrates. You know, in the future, I think that might be something to test, but diabetics have special nutritional needs and lower carbohydrates and certainly lower glycemic index of the carbohydrates they eat would be advisable.

Arthritis Today: Everyone’s goal [in the study] was to try to reduce their calories by 750 a day.

Dr. Sacks: Right, unless it got below 1200. So, for example, in a small woman who’s not so active, we don’t want calories to go below 1200. So with that proviso, the prescription was calorie needs minus 750.

Arthritis Today: But most people didn’t get that far, did they?

Dr. Sacks: Initially they did, like the editorial said, but over time they began to eat more, so they didn’t maintain that kind of caloric deficit, but that’s fine. I mean, for example, if you take a person who wants to lose weight, if they went down 250 calories a day, they’d lose a lot of weight over a period of a year, so you don’t really have to have minus 750.

Arthritis Today: You did counsel your participants to exercise, too, right, but it wasn’t very much, as I recall. It was about 90 minutes a week?

Dr. Sacks: Ninety minutes a week. Here’s the rationale. Exercise and weight loss has been very well researched and what the results say is that for losing weight, exercise has a very minor role. But for maintaining the weight that’s lost by nutrition, exercise has a very important role. So we wanted exercise primarily to kick in for weight maintenance. So our participants were mostly obese. They were not very well conditioned. They were not an exercising bunch of people. We had to start very slow and work up.

The purpose of the study was not exercise. It was to test different diets

Arthritis Today: That’s so interesting because people think you have to go to the gym and you have to kill yourself but it actually, at a certain point, becomes counterproductive to weight loss, doesn’t it, because it increases your appetite?

Dr. Sacks: That’s the problem. The studies have shown that people basically eat back some of the calories they burn off. So, the net calorie deficit from exercising is very small, but for producing weight loss, it just doesn’t cut it, but for maintaining weight loss, a small calorie deficit day after day after day is really quite relevant.

Arthritis Today: Have you ever tried to lose weight yourself?  

Dr. Sacks: Yes. Over time, my weight crept up. I had some knee problems and I couldn’t do my usual running. I just hadn’t worked out some alternative, and then in my work, I wound up traveling so much that gradually I gained weight. I gained 15 pounds, and after several years I said, well, I didn’t want to stay that way.

It really took a concerted effort. I lost 13 of those 15 over the last several years.

It’s not an easy thing. You’ve got to really think about what you’re eating and make some changes. Get rid of higher calorie foods in the house that aren’t that nutritious. You can use your imagination about that. Get rid of that stuff so it’s not there, if it’s not there, you’re not going to eat it. I had to take a look at when I was eating more than I needed to eat and what were the patterns and then how to change those. Eating huge meals out on the road when I had less control over it. Just being fed these buffets for breakfast to say, ‘Wait, what are you doing here?’ They are serving it, but I don’t have eat it.