'Fast Diet' Creator Discusses Controversial Methods on 'GMA'

Dr. Michael Mosley responds to critics who suggest days of fasting could slow metabolism.
5:18 | 03/19/13

Coming up in the next {{countdown}} {{countdownlbl}}

Coming up next:



Skip to this video now

Now Playing:


Related Extras
Related Videos
Video Transcript
Transcript for 'Fast Diet' Creator Discusses Controversial Methods on 'GMA'
The British guys that. How taking the US fight the war. No government has new diapers and it's all coming that came over from England watch what you -- two days a week and eat what you want the rest. It's called the fast -- And within a week of US publication in January and following its exclusive GMA appearance and take a look at this -- -- This. Two days a week it's now a New York Times best seller. Amazon.com reviews have customers -- screaming I feel like I finally found an eating plan I'll be following for life and already lost almost four pounds after two weeks of doing the fast diet. Fans of -- -- report giving radically healthier by fasting not every day just two days a week -- other five is required no will power. You can eat what ever you want. I think I have pain and come across on the -- and dancing tweak the pounds don't. UK resident -- McLaughlin says she lost 36 pounds over seven months but some nutrition experts say it's impossible to know the die in a safe. Without more human testing. Not safe for somebody under twenty. -- or somebody -- growing or for kids. You know sit and it may not be safe for all adults is as well but says her dress size isn't the only thing that's changed my appetite -- this case. Side will be what I -- Eight sometimes find it quite Sunday. A lot of people talking about this dietary as the man behind it doctor Michael Moseley is joining us now live first television interview here in the states thank you for being here at the pleasure I just want to remind everybody so your diet says that you can eat normally five days a week and to lose weight of women limit themselves on the other two days to -- calories and then limit themselves to 600 calories. A day and you say that that has actually plenty of calories yes and. Examples accidentally -- -- food of nutrients this is a breakfast -- ultimate male. And lots of delicious blue -- That would be about 250 calories and also have an orange. Not orange juice because -- about fiber and that's important. -- -- big plate of food -- lots of vegetables and also some delicious chicken so this is all you get a -- that's what -- the whole -- how do you -- -- it out. Basically -- for breakfast at about some that in my family and then I have them. Evening -- and -- with my wife and kids. And that I think lots of that this is for a woman from -- and you can go further than -- -- for example on would have instead of that have a couple of scrambled eggs that. And I find the protein keeps me full -- actually find first few weeks a bit tough enough to let it get better. And you mentioned again all cavalry is not treated equal so what food should we be. Looking for on -- days and perhaps avoiding essentially what you -- here is a mixture of vegetables and -- approaching we'll keep you full vegetables you can get an all -- -- look at that. That's probably an about 250 calories and that is quite substantial and hilarious substantial meal that Sony connect look at that what delicious really tasty not to count those lots of flavors. And that's important might be to be committed I don't want to ask you as if this. Look at this stuff but the bad stuff okay this is what the cool high -- and nick. This is full of calories but it put a couple hydrant put sugar is what's surprising for example and take you think potatoes healthy. But actually baked potato will -- your blood -- is up of -- tablespoon sugar and very quickly you actually came upon this diet it's a bit accidentally what we looking to do. Well what happen. Happened about a year ago I discovered when I went to see my -- that my blood -- -- world wait to hunt. She said essentially a diabetic and Mike -- but would wait to mine so I decided -- getting on drugs I would -- -- look for solution and I went and visited. A whole bunch both American were such. Stations and they suggested intermittent posting and then this -- -- the. I want to talk with the -- really quickly Josh on because medical professionals some are saying. That this can actually be potentially dangerous and slow down your metabolism so please do tell us lot of questions yet what are the drawbacks. Okay that is not true basically all metabolic rate will actually speed up briefly. That only if you lost four days a week to -- likely to have that problem. This has been studied extensively lots of human trials. Who also studies that the US and the UK should be put that thing drop people can probably shouldn't. And they would include pregnant women women who breast feeding people who have issues around weight and I would recommend it. The teenagers. Broadly speaking you wanna ask a lot of questions -- -- from Texas how important is drinking lots of water very very important because you. Frequently particularly but actually just dehydrated so water that -- -- that Kofi. -- the -- a lot of people don't like to drink water they want to drink soda something heavily is there anything that can quote it put it. Suddenly want to with a bit of damages and it's delicious thank you Jeanne -- Lindsay Oklahoma has this question would it do more good fast three days a week -- is that not recommend. I tried -- festival because there are studies that suggest that you actually will lose more weight but I found it too extreme so I went to two days because that -- more moderate more sustainable. And it -- these development maintenance that should one -- we. -- a lot of questions answered if the fat -- -- it's in stores now you can get the recipes for the meals you just saw here at Good Morning America dot com on. Product but -- --

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

{"id":18763080,"title":"'Fast Diet' Creator Discusses Controversial Methods on 'GMA'","duration":"5:18","description":"Dr. Michael Mosley responds to critics who suggest days of fasting could slow metabolism.","url":"/GMA/video/fast-diet-creator-discusses-controversial-methods-gma-18763080","section":"GMA","mediaType":"default"}