Mel Robbins is a CNN commentator, legal analyst, best-selling author and keynote speaker. She also is a contributing editor for Success magazine. In 2014, she was named outstanding news talk-radio host by the Gracie Awards. The opinions expressed in this commentary are hers.

"Holy cow, he looks so different."

My teenage daughters were staring at their phones, so naturally I was curious.

Who are you talking about? I asked. They held up their phones and showed me a photo of some guy leaving a personal training session in blue sweat shorts.

"Who is that?"

"Jonah Hill!"

"That's Jonah Hill? From 'War Dogs'?"

"Yup."

"Holy cow, that doesn't even look like him!"

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Between Beyonce's twins and Jonah Hill's transformation, the Internet has had a much needed surge of celebration. Why the collective kvelling? Hill not only looks great, but it's also downright inspiring to see such a dramatic change on a nice guy.

Plus, if you read between the lines, he also gives you the secret to how he did it:

1. He asked for advice from a friend who's in great shape.

That friend? His "21 Jump Street" co-star Channing Tatum.

"I wanted to get in better shape, so I called Channing Tatum and said, 'Hey, if I ate less and go to a trainer, will I get in better shape?' " Hill said during an interview on "The Tonight Show Starring Jimmy Fallon."

Tatum's response? "Yes, you dumb mother****er, of course you will. It's the simplest thing in the entire world."

That last line is the most important one. It's the mindset that is absolutely key to successful weight loss. That is ...

2. It's simple -- don't over complicate it.

As Tatum said: Losing weight and transforming your body is simple.

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That's true. If you stick to a calorie-restricted diet and maintain a consistent exercise routine, you will lose weight.

If you add a personal trainer or nutritionist to the mix, you'll have accountability, and you'll lose even more.

The problem with weight loss is rarely the diet you choose -- it's your inability to stick to it. We over-complicate things, and we let our emotions determine what we eat or whether we'll exercise.

That's probably why Tatum described the process of getting in better shape as "simple" -- not "easy."

3. Hill kept a food journal.

Research published in the American Journal of Preventive Medicine has shown that people who keep a food journal lose twice as much weight as those who don't keep a log of their meals.

Hill, who has attempted weight loss before, told Jimmy Fallon last year that he relied on a food journal to keep him on track -- even accidentally texting his daily food diary (intended for his nutritionist) to rapper Drake.

"He did not write back. Another guy I have to duck for the rest of my life. On the long laundry list of people I'll never speak to."

Don't you love how he doesn't take himself seriously? Laughing all the way to a healthier body sure sounds like a much better way than suffering through it.

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Speaking of suffering, many of you are wondering on social media whether this slimdown will affect his career. In 2011, Barbara Ellen speculated about this too in the UK paper The Guardian: "Post-weight loss, Hill has emerged as kind of half-buff, neither a fully fledged slob or, as is technically known, a hottie. In Hollywood, isn't this tantamount to career suicide?"

And fellow fat-to-fit comedian Seth Rogen once said, "You probably all notice that I'm around 10 pounds less funny" after his own weight loss.

My take -- Jonah Hill knows what he's doing.

Sure, he's typically cast as the overweight funnyman, but his major weight loss in 2011 was for the more serious movie "Moneyball" and shows that audiences love his dramatic side.