Identical twins try out 2 trendy diets for 30 days

As part of the "GMA" Twin Test Lab, one twin tried out the Whole30 diet while her sister tried out the counting macros diet, and they revealed their weight loss results live on "GMA."
5:03 | 11/14/17

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Transcript for Identical twins try out 2 trendy diets for 30 days
Two identical sisters who live nearly identical lives trying out two different diets. Take a look. ??? two twins Lauren and Leila. Two trendy diet, whole 30 versus counting macros. Which works better. We began at St. Luke's mt. Sinai tofigure out their starting numbers and put them 5 in a bod pod. It can show you how much fat you have on the body. The scale is not an indicator. It's the fat in your body. Reporter: Experts suggest 30% body fat or less for women to obtain good health. Percent body fat is at 37.9. That's not good. That's not good. Reporter: Lauren's starting weight, 152.3. Body fat, 41.2 and leil's weight, 133. And body fat 37.9. Lauren is taking on the whole 30. Coaching her through is whole 30 co-creator Melissa hartwing. The whole 30 is tote Aly different and look at it as a reset. Pushing it with your health, your habits and relationship with food. For 30 days of whole food, meats and veg tack, no sugar, no alcohol, no grains, legume, soy or dairy. So what we do is pull them out for 30 days and it's a pretty strict pullout. You do have to stick with it. Reporter: For Leila, referred to as counting macros. It's the new school way of counting calories. There's three macro category, preteens, tarabasovs and fat and have the correct amount is the thing. Reporter: She's being coached by this couple. Preparation is huge. Reporter: Leila can fit whatever she wants as long as it fits into her pie graph. We recommend 80% of your day is nutrient dense foods. Your fruit, veggies, complex carb, lean meats and leaves 20% to be anything that you want. Ice cream. Reporter: Both twins tackling their first week stocked with food for their diet. For 30 days Leila weighing everything she eats and checking the macros and making sure to stay in her numbers. And Lauren cooking everything, making sure to stick with the foods allowed on the whole 30. And today it's been 30 long hard days. But was it all worth it? It is time for the results. All right. So we have Lauren, we have Leila and Maya feller here. So, Lauren and Leila. We want to see results. Please step on up and start with Lauren. You started at 152 pounds and Leila you were 133 so let's see where you are. Drum roll, please. All right. Here we go. Wow. Congratulations you guys. Can we look. What is it? So, Lauren you lost over ten pounds. I did? 7% of your body weight. Oh, yay. Congrats and Leila, you're down so cute. More than 6 pounds, 5% of your body weight but she's started at less weight so let's see what happened to body fat percentage. Oh, lord. Drum roll, please. Thank you, audience. Very nice, very nice. All right. So this is amazing. Lauren, you lost 5.1% of your body fat. Leila, you lost 4.6. Oh, yeah, good. Congratulations. Come on down so those are remarkable and I'll ask Maya how scientifically acura is the twin test. This is completely anecdotal based on these two girls. Not something we can generalize. Lots of variables and factors. Their age, their initial weight, hormones that play into how they lost weight, right. Doing it with identical twins, doesn't that help us see which diet works better. Not necessarily. As I said there are different variables so you would see, you know, for one of them they had different outcomes versus the other one. Okay, so I'm going to ask. Lauren, how did you feel about the whole 30 diet? Would you recommend it. I would recommend it. Only thing it was a little difficult at the beginning because I had to take out dairy and sugar but after -- I know it was a little tough. After the first two weeks it was pretty simple. You sort of get used to it. You did counting macros. Doing research on it it sounds like it's a lot of work. Well, the counting macros was great but the work was me like weighing my food and having to log everything that I ate every day was the most challenging part. Takeaway, would you recommend it. I'm still doing it and recommend it because it's flexible. Sticking with it. Yes, love it. I got to thank you, Maya. We'll keep doing these experiments. Keep up the great work. Thank you. I'm just figuring out who is who. We'll head right over to Michael

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

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