"I tried a lot of diets before. I tried Paleo, I tried a little Keto. I needed something that was going to keep me accountable, even though I have to do the work, because I've failed in the past," said Rosenthal of Fullerton.
Like many 20-year-olds, he spends a lot of time on his phone. So he searched for an app to help him shed the weight.
He discovered "Lose it," an app that helps you track your food and exercise, which is free for the basic plan. He dropped 130 pounds.
"It gave me an idea of how much I could eat in the day," said Rosenthal.
Rosenthal combined the calorie counting with using a Fitbit for walking. He used one app for keeping calories in check and one to keep his activity accountable.
"It reminds me to get up every hour and take steps to get my steps in," Rosenthal said of his Fitbit.
And while that seems to be his winning combination, nutrition expert Dr. Jonny Bowden says there is more to it than that.
"The first thing I would say about Jeffrey or anybody like that is that you never argue with success. But I would say for most, calorie counting is kind of yesterday technology," said Bowden.
While Bowden agrees that calories count, it's important to look at the quality of those calories, which are equally important for your body's blueprint.
"We now know what's in those calories stimulates hormones and hormones are really what's running the show. Hormones are what tell your body to store fat. Hormones are what tell your body to burn things down or build things up. Hormones are what build muscle," said Bowden.
This is a big reason why cutting back on calories alone may not be enough to lose weight. Rosenthal still keeps things simple, but now keeps a food journal and checks out the calorie count on menus when he eats out.