Medical ethicist and author Art Caplan stopped by Boston Public Radio on Wednesday and had some interesting things to say about Fed Up, Katie Couric's new documentary about sugar and its close causal relationship to childhood obesity.

Caplan offers a counterpoint: calories are calories, and while some calories are better than others the trick to fighting obesity is primarily to eat less, but also to eat better.

Here are some nuggets from Jim Braude and Margery Eagan's conversation with Art Caplan:

Jim Braude: We've discussed Fed Up with virtually every guest we've had on this week. Essentially the title we've given it is "Sugar Kills." It's about obesity in America, particularly childhood obesity. For those of us that have been dieting off and on our whole lives-- it's always been all calories are created equal. Is the message of Fed Up that all calories are not created equal? Should that be one that we take seriously in terms of our health and our fitness and that sort of thing?

Art Caplan: I don't think all calories are different. I think a calorie is a calorie, whether it comes from sugar, or carbohydrates, or chewing on cardboard-- whatever the caloric value of the thing-- and I said chewing on cardboard because that's my attitude about a lot of the diet stuff that I've tried to eat over the years.

What I think the message may be is that there's a lot of hidden calories out there. That there is corn syrup and other sugary additives and products-- from ketchup, to who knows what. There's places that you don't know that they're putting in a lot of sugar. I don't think the proper message is that there are certain evil calories. At the end of the day, your body doesn't care where they came from it just cares how many you ate. So that's the key to obesity reduction. But you do need to be alert, and I think the passage is partly there that there is a lot of hidden calories. That's probably what they're getting at.

JB: But isn't part of the thing that if you have a comparable number of calories from something that's healthy-- nuts and so on, and have the same number of calories from sugar. The nut and vegetable calories don't lead you to go back for more, but the sugar calories have a certain addiction thing and they do cause you to go back for more.

AC: There is truth in that, and it's certainly true that some calories are more nutritional than just eating my favorite candy bars, or something. But at the end of the day, you still can't go out and eat-- people say "Well, I'm on a diet. I'm going with cereal in the morning. No more donuts, I'll just have my six bowls of cereal before I get going here."

It's sort of like- what? Even if it's muesli or something healthy, you can't eat six bowls of it. But that's my only point, so yes, you're absolutely right. Some foods fill you up more, some food leaves you with a longing. I think you can get addicted to the sugar high. I get all that, I just want people to understand at the end of the day, you don't need the diet book and all that, you just got to eat less calories. 

Check out arts editor Jared Bowen's review of "Fed Up" below: