Transcript for 'Fed Up' With Sugar: Katie Couric's 10-Day Challenge
It's been called dangerous. It's been called addictive. And it's in almost everything we eat. Sugar. Tonight the food industry is up in arms over a controversial new movie accusing big food of peddling unhealthy sugar-filled products, especially to our kids. And tonight this challenge. Could you go sugar-free for ten days? Is that even possible in I tried it. And the results were surprising. It is a controversial new entry into America's raging debate over obesity. What if our whole approach to this epidemic has been dead wrong? Reporter: The new movie "Fed up" says the country has gone way off course, blaming obese people including children for their weight problems. The message has been pushed on us, it's your fault you're fat. Reporter: Instead, according to the movie, the real problem is the food companies who load their products up with sugar, which critics call dangerous and addictive. Sugar is poison. Diabetes. Heart disease. Lipid problems. Strokes. Cancer. Those diseases are being driven by sugar. If a foreign nation were doing that to our children, we would defend our families. Years from now we're going to say I can't believe we let them get away with that. Reporter: According to the movie, most Americans are hooked on sugar. And truth be told, I am one of them. Cookies, cheesecake, jellybeans, they seduce me every time. Okay. So I'll admit that I'm one of these kind of annoyingly healthy people. I work out every day. I eat a lot of fruits and vegetables. I don't smoke. I don't drink. I don't even drink caffeine. I have one major vice. And that is sugar. Reporter: So you can imagine my discomfort when my colleague Katie couric, who's the narrator and executive producer of "Fed up," announced something called the "Fed up challenge." Ten days with no sugar. I'm going to start on Monday. Reporter: She then went on "Good morning America" and publicly roped me into it. And Dan Harris of "Nightline" is going to be doing it with me. Reporter: Thank you for that, Katie. So here are the rules of the challenge. No soda or sweetened beverages. That includes diet soda and juice. No artificial sugars or sugar substitutes. And no foods that have added sugar, which includes not only my favorite desserts but to my surprise everything from yogurt to canned foods to spaghetti sauce. Okay. So it's the Sunday night before Katie couric's sugar-free death March, and I'm doing a last-minute binge. Cookies. Mm. I'll miss this. Reporter: Sure enough, the next day, day one of the challenge, I'm missing sugar already. Everybody's having chocolate. And looks happy. And I'm having fruit. Reporter: Fruit, which has natural sugar, is allowed under the rules of the challenge. I'm not cheating. I just want you to know this is unhappy face. Reporter: My only consolation? Katie is suffering too. I'm feeling a little listless and lethargic. I want a cookie. You know, I think I miss the sugar. I'm not going to lie. Reporter: As soon as you decide to cut out sugar, you very quickly realize how hard it is to find any product that doesn't have sugar. I look at my super healthy bread to take a piece of toast this morning. And I was so bummed. Look. One gram of sugar. Ah! Everything has added sugar. Reporter: According to the movie, even if the label doesn't say sugar, don't be fooled. There are 256 different names for sugar. Day 5, we bring Dr. Mark Heimann, featured in the movie, to a supermarket. You have to learn how to hunt and gather especially in a supermarket, and the best way to do that is to stick around the edges of the supermarket. So don't go down any of the aisles, where all the processes foods are. Reporter: He says there are 600,000 food items in America and 80% have added sugar. It's very simple. If you read a label and it's an ingredient you can't pronounce, it's in Latin or it's not a real food, put the food back on the shelf. Is there a bar code on this? Right? Is there nutrition facts on this? Reporter: It's a little bit more work than just buying a frozen dinner, but Heimann says the trick to going sugar-free is cooking your own maelds. We ate ourselves into this by eating junk food and we have to cook our way out of this problem. Reporter: So does this mean I can just bake lots of homemade cookies and cakes at home? Apparently not. I love dessert. Yes. You've take than away from me. Oh. We think we love cookies, we love donuts, we love cake. But I've got news for you. It's not love. It's addiction. In animal studies they found that sugar's eight times as addictive as cocaine. When they put rats on eating sugar in a little sugar bowl with little sugar and then they put them on an electric shock pad and they shock them while they keep eating the sugar, they keep eating the sugar while they're getting shock citing shocked because it feels that good. So I'm the rat in this -- You are. You're the rat. Reporter: On day 7 my co-anchors on "Weekend gma" are openly taunted. Hands down the best thing I've ever had. You guys are really good friends. Reporter: Even if you happen to have nicer colleagues, we all live in an ecosystem of near constant temptation. Bombarded by marketing messages. Especially kids. On television and even in school. In the movie Katie challenges former president bill Clinton about why the government hasn't done more. Do you think the government is behind when it comes to helping Americans reduce their sugar intake? Yes. I do. Why? Why are they doing that? Or why aren't they doing more? I can't answer that. Reporter: As you might imagine, the food industry has not taken kindly to this movie. The grocery manufacturers association arguing that companies have aggressively reduced calories, that childhood obesity has actually gone down in recent years, and that the movie just plain gets the facts wrong. Still, while critics may take issue with the movie's, quote, vilification of one nutrient, pretty much nobody argues that reducing sugar is a bad thing. Day 9. And dietary freedom is so close I can almost taste it. I will admit that I am sleeping a lot better without all the sugar. But the cravings have not diminished one bit. In fact, on my way home from work I pass all of these tantalizing dessert places. I feel deprived. I felt very angry at Katie. This morning, the day after the challenge ended, I went on "Good morning America" with Katie. Are you going to stick with it? You know, I think I will stick with it with a few calculated sugar binges. Reporter: People had asked me did you cheat? The truth is I did find a box of Swedish fish my wife had hidden away in the cabinet, and to my great shame I had two of them. But again, I only had two of them. Now, we should say that grocery manufacturers association contacted us to say that "Fed up" provides an inaccurate view of the packaged food industry and "Our companies have been trusted by generations to provide products that are safe, nutritious, affordable, and well balanced." "Fed up" is in theaters right now.
This transcript has been automatically generated and may not be 100% accurate.