Transcript for Inside the #GainingWeightIsCool fitness trend

Now we go to a fitness trend taking off on social media with the #gainingweightiscool and focus on the health instead of the number on the scale. Eva pilgrim is here. None of us like the scale. It's not anything we usually want to get on. Who hasn't dreamed of ditching their bathroom scale? That's exactly what fitness blogger did and,000s of women may be following suit. ?????? the dreaded scale. For so many it's made weight loss all about the numbers. Like so many women I went through the I want to work out to be skinny and fit into a certain size. Reporter: But now move over, scale. A grassroots fitness trend is popping up all over social media using the #gainingweightiscool many instead of focusing how much you weigh, a new shift in emphasizing overall health. It started when this photo was captured gaining weight is cool. I gained like 20 pounds and like that whole year I was super depressed about it. Reporter: She gained some weight and realized she didn't look terrible after all. When I looked back at the pictures I didn't see 20 pounds. Reporter: It blew up from there. Getting hundreds of responses like thank you for helping me realize that gaining weight is okay and I am so on board with this. #Idontweighmyselfanymore. I get messages from women telling me that it helped them. Reporter: With the nation's obesity epidemic on the rise Harley Pasternak says the message is right, but with at?? small tweak. Hashtag don't weigh yourself is cool, hashtag live a moderate healthy lifestyle is cool. Reporter: He thinks no good could come from getting on that scale. That can affect you and make you depressed and do extreme things as a reaction to seeing that number. Reporter: Many medical experts say the scale is a useful tool initially to evaluate health on a weekly or monthly schedule but day to day it's not helpful. Do not Tortu yourself getting on the scale every day, people. I think we all have done that and most people at home have done that. Thank you for that, Eva. Dr. Ashton, you have a degree in nutrition. If you ditch the scale what other ways can you track your fitness. There have been studies that show people who regularly weigh themselves are better at maintaining their but it's not just about that number on the scale. You guys know as former athletes, muscle is a dense tissue and you can be very healthy, very fit and see that number go up so I think the things you should look at. How are your clothes fitting. Can you walk or run up stairs without being completely winded. How strong do you feel and objective measures. You have to know your blood pressure numbers and total cholesterol and blood sugar. Remember, you can be very unhealthy with a low weight number just like you can be healthier with a higher number. Is there truth to when people say muscle weighs more than fat? It's definitely a more dense tissue so when you see people hitting the weights, take a feel for the guns. Whoa. You can see, you can see that -- You should get a license to carry that. It's just part of the picture so, again, we really have to strike for a middle ground here how you feel and not just those -- what size are your jeans. I got off the scale and judge this by the button on my suit. If it feels like it'll fly off and hit an audience member in the eye, I have to cut down on the doughnuts. Thanks. Over to ginger. Good morning.

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