Do Diet 'Cheat Days' Really Work?

JD Roth, author of "The Big Fat Truth," and Dr. Jennifer Ashton delve into the science of "cheat days" and whether they can help or harm dieters.
5:21 | 05/31/16

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Transcript for Do Diet 'Cheat Days' Really Work?
Now to our weight loss win series. This morning we're breaking down the science behind cheat days. I cheat. I don't feel so good about it but I wondered do these indulgence days hurt or help my diet. ABC's Mara schiavocampo is getting to the bottom of it all. Reporter: Cheat days, an indulgent break from the drudgery of dieting. Often shared on social media. For the rock, mountains of fudge, peanut butter brownies and cinnamon buns. Jennifer aniston goes for Mexican food and for the Kardashian, boxes of fried chicken. What do you see them eating. Chips to cookies to popcorn. Chocolate, cakes, huge sandwiches. Pizzas, ice cream. You name it. Reporter: But can giving in to cravings one day a week help your diet or hurt it? The science is hazy but some say cheat days may help by upping production of the Hore lone. Will eptin, decreasing appetite and helping the body burn more calories after overeating by increasing metabolism. A psychological benefit. You can feel motivated to stick to your diet plan because you know you'll have a day where you get to eat a little bit of whatever you want. Reporter: But for a lot of people these days may actually be counterproductive. You gave me a full day to eat whatever I wanted I could ruin weeks of good work. Absolutely. You could take in upwards of 5,000 calories. That would be a disaster. Reporter: Experts say it can also be hard to get back on track with a cheat day turning into a cheat week. When I counsel my patients I actually don't talk about using cheat days. I talk more about moderation, have one meal that is a little bit more decadent. Reporter: For "Good morning America," Mara schiavocampo, ABC news, New York. All right, joining us now with more ABC news senior medical contributor Dr. Jennifer Ashton and J.D. Roth, author of "The big fat truth." We're going to find out the truth today. Yes, we are. Now, Dr. Ashton, you're board certified in obesity medicine. Now you have your masters in nutrition so what is all the data telling us about dietary approaches to weight loss. First of all in the medical nutritional science and behavioral science literature there is no term cheat day. That's something we make up in TV land and society and our every day-to-day life. What the data does show you know what the best diet is, the one that works for us. Okay, so that's very, very important and then we have to remember that the term cheating is very subjective. For one person it may be one cookie ever for another person it might mean the entire bag of cookies so very subjective. I'm not going to tell you which person I am. Now, J.D., you're an executive producer of "Extreme weight loss" and contestants are given one cheat day. You don't necessarily agree with Chris Powell. In six years it's the only argument we have gotten into. He's one of the greatest trainers on the planet, right? An excellent guy. Here's my issue. If you are a recovering alcoholic, do you go into ray bar one day a week and have a drink? No, because you can't just have one. And the people I deal with are food addicts. They need to change their relationship with food and to have a Sunday fun day, a day full of comfort food comes with a side of remorse after it's over and that's the part I have to deal with. A slippery slope. What happens is you start restricts calories prior to your fun day then fun day comes and it's on eating as much as you can then you have to restrict again and now you're restricting and bringing and now instead of just being overweight now you're an overweight person who has an eating disorder and that's the part I worry about. It's interesting that J.D. Mentioned something we now talk a lot about in the weight loss world and obesity medicine world which is the parallel between having a substance abuse problem like alcoholism and a principle that is well known in that world substance abuse, addiction world called harm reduction and what harm reduction means it's kind of think of it as the difference between idealistic versus realistic saying we're going to agree that that behavior is going to occur. It gives you strategies to minimize the negative consequences that come along with that so if you're talking about alcohol, you're going to drink, don't drink and drive and they're using the same principles with things like overeating so a different approach in my book the best E diets are safe, simple and sustainable so you can stick with it. Working small incidendulgences in -- oh, I can't have dessert, I'm on a deet. Here's what you can do, be in control so order your dessert, have one or two spoonfuls, open up the salt shaker -- We just ordered some. And dump salt all over your dessert. That gives you a sense of control. You want trick, here's a trick, fill up, give yourself the control and fill up a small Dixie cup. Put a little bit of chocolate ice cream. Make one for Monday, one for Tuesday, Wednesday, Thursday, Friday then you know that's all you can have. You eat that. That puts you in control. In the end what you per self as hunger pain is really emotional pain and you need to manage that. Well, thank you both for sharing. This is very important. Hand over the ice cream.

This transcript has been automatically generated and may not be 100% accurate.

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