In the health conscious supersize me era, it's common knowledge that fast food can be bad for your health and your waistline, but today, bad news for those who believe ka lotter ignorance is bliss, as... See More
In the health conscious supersize me era, it's common knowledge that fast food can be bad for your health and your waistline, but today, bad news for those who believe ka lotter ignorance is bliss, as McDONALD'S ANNOUNCES THAT Calorie counts are going to be posted on their menus nationwide. So, abc's dan harris decided to hit the golden arches and see how a little menu math might change the way americans chow down. Reporter: Americans spend $100 billion a year on fast food. We consume three burgers a week on average. So, will we start making healthier choices once McDONALD'S STARTS POSTING HOW Many calories are in its meals, as they've just announced they will do beginning next week? This put us in the mood to do an experiment. Step one, I'm going to go in this McDonald's and make my dream order. This is very exciting for me. I love burgers. Double quarterpounder with cheese. Large fries. And a vanilla shake. Some of the calorie information McDONALD'S WILL BE POSTING IS Quite surprising. The big mac is not the biggest source of calories, just 550. That'sless than the double quarterpounder with cheese at 750. The highest calorie food on the menu isn't even a burger. It's the big breakfast with hot cakes. 1,090. What's the damage in my bag? Grand total, 1,950 calories. Now, step two in this little experiment. How much time will it take me to burn off 1,950 calories on this treadmill? Okay, so, as the experiment runs its course, let's consult some experts on whether forcing restaurants to post calorie information, as the federal government is poised to do soon, actually works or whether it's just another example of the nanny state run amuck. All right, doctor -- yes. Reporter: We brought you here to McDonald's because we have a question. This doctor is from new york university. He has done studies and found that posting calorie info does not change the way people order. What do we have to do to get people to really change their orders? Offer a defibrillator with the burger? These foods really taste good, so, the price is a huge factor. We know convenience is a huge factor. All of these things come into play. Reporter: To be fair, there have been conflicting studies showing sometimes calorie info does have an impact and the doctor says it may become increasingly effective over time. Meanwhile, back on the treadmill -- I've been running for ten minutes now. And I've only burned 115 calories. Which is a little depressing. Time to speed it up. So, what elsean we do to curb the american appetite ins a country where two-thirds of us are overweight or obese? What about that law in new york city, banning the sale of sugary drinks over 16 ounces? The doctor thinks that could actually do some good, even though many protesters really believe this is big government out of control. But as the doctor points out the, the nanny state has been effective at things like bringing down smoking through taxes and cigarette bans. You're saying we've got so many people sick, so many people costing us so much money in so many hospitals across america because of obesiobesity, we have to do something. If it infringes on your liberty just a little, deal with it? It's a ball lapse, right? I don't think anyone is saying that fast food restaurants can -- I don't think anybody can saying that certain foods cannot be sold at all. But to make changes that are subtle or a little more than subtle that might shift your behavior just a little bit. Reporter: Finally, the results of the experiment. Okay, I'm at 30 minute, nearly 400 calories. And I quit. At that rate, I would have had to run more than two hours, which is never going to happen. Unless I'm being chased. I'm not going to lie. It's a sobering statistic. But I'm still going to eat the burger. For "nightline," this is dan harris, on the treadmill.
This transcript has been automatically generated and may not be 100% accurate.