LAS VEGAS -- During a post-fight press conference on June 13 in Mexico City, UFC president Dana White said he was the "furthest [thing] from confident" that Kelvin Gastelum could cut to 170 pounds.
What changed? According to Gastelum, the UFC agreed to book him to the welterweight fight only after a phone conversation between he and White, during which Gastelum promised to hire a full-time nutritionist.
"I asked for the fight against Matt Brown," Gastelum told ESPN.com. "At first, [UFC matchmaker] Joe Silva told me no. A couple weeks later, Dana called. He actually gave me the fight I wanted against Matt Brown in Monterrey and told me, 'You better make 170.' I said, 'Send me the contract right now, I promise I won't let you down.'"
Gastelum, 23, has enlisted the services of nutrition expert George Lockhart ahead of his return to welterweight.
He fought in the 170-pound division five times between 2013 and 2015, but had several issues making weight. After he weighed in at 180 pounds for a high-profile fight against Tyron Woodley in January, the UFC informed Gastelum his next bout would have to be at 185. He fought Nate Marquardt at UFC 188 in June, and picked up a TKO win over the former title contender.
Despite the strong showing at middleweight, Gastelum has always maintained his future is in the welterweight division.
"I hadn't proven, to that point, that I would be willing to cut to 170, so I think [White] was right," Gastelum said. "He did kind of a punch to the face [with his comments], but that's fine. Sometimes you need that.
"It has taken me awhile to learn the process of how nutrition and dieting works. I've learned from mistakes. I've grown from it. Now, I need to apply it."
As long as Gastelum can comfortably make 170, his future is bright in that weight class. He submitted Jake Ellenberger in November last year and came up just short in a split-decision loss to Woodley two months later.
A scheduled five-round fight against Brown (20-13) is guaranteed action. Brown, 34, has won three fight of the night bonuses in his past six appearances.
"You pretty much embrace it's going to be a war," Gastelum said. "So, that's what I'm going to prepare for -- a 25-minute war. Obviously, you want to the win as quickly as possible but I know that's not the case with Matt Brown. He has fought the best in the world. He's one of the best in the world. I feel like I've gained experience, I've made mistakes and grown from them and I feel now it's my time to really make a run.