Author of the book Dr. Bert Herring explains the diet in five simple words.
"Eat within 5 consecutive hours."
For the other 19 hours you're only allowed no-calorie drinks such as water, diet soda or green tea.
Within the 5 eating hours, Herring says people can eat whatever they want including junk food and chocolate. But he still recommends healthy foods too.
Carmen's goal is lose 5 to 10 pounds.
Randi, who is plus sized model, wants to lose some weight but her main goal is to be healthier.
Dr. Herring admits the diet is difficult in the beginning but says after three or four days that changes.
"All the sudden they're free, they're no longer rotating their lives around food."
He says it's based on the principle of hunters and gatherers who had to search for food and fast when it wasn't available. He says eating this way will even out your appetite so that you only eat what you need. Then your body will go down to its ideal weight. It's how he lost 20 pounds and has kept it off.
"You don't have to check the scale; you don't have to count calories it's all on auto-pilot."
He says it takes about three weeks for your body to adjust then dieters can start to expect losing about a pound a week.
Carmen stayed on the diet for 4 weeks and sure enough at week 3, she saw results.
"Then all of a sudden it just came off, I lost like 3 pounds and it seemed to be overnight."
In total, Carmen lost 5 pounds in 4 weeks and is happy with her results but says it was a struggle.
We caught up with Randi five weeks later while she was doing a photo shoot for Catherine's. She's still on the diet and loving it. She doesn't weigh herself but says she was ecstatic when she realized her skinny jeans are now loose.
"I was like 'they fit, they fit' I was doing the whole shaking thing and sliding then up and down without unzipping them it's nice."
So far Randi says she's lost an inch and a half to two inches off her waist and an inch off her hips. She plans to stay on fast five at least 3 to 4 days a week.
Dr. Herring says the diet is meant to be a lifestyle change not a crash diet.
Nutritionist Andrea Spivack of Penn's Stunkard Weight Management says while there are some things she likes about the diet she wouldn't recommend it.
"Fasting for long periods of time is it healthy? There's really not the evidence to support medically this is the way to go."
Carmen agrees and says she wouldn't do this long-term.
But Randi says for her, it makes sense.
"I can't explain why it makes sense but it does," she said.
As for whether it is healthy Dr. Herring says there are studies that show animals that eat fewer calories live longer, healthier lives. And he says you may binge at first with this diet but as your body adjusts, you will eat fewer calories and that's how the weight loss happens.
Another interesting thing about the diet book is that Dr. Herring has made it available to download for free, just click here.
This diet is not recommended for everyone especially not for diabetics. You should always consult your doctor before starting any new diet or exercise plan.
