Anthony Joshua punched by Andy Ruiz Jr. Photo / Getty

Andy Ruiz Jr. may not look like your standard heavyweight champ, but his seemingly out-of-shape exterior might actually be an advantage.

The Mexican-American shocked the world by knocking out the previously undefeated Anthony Joshua to claim the IBF, WBO and WBA world heavyweight titles.

To the untrained eye, the upset victory seemed even more unlikely when lookin at the fighters' contrasting body types.

But according to sports nutritionist Dr Mayur Ranchordas, there are many benefits to carrying extra body fat in professional boxing.

"In a sport like heavyweight boxing there are certainly scenarios where carrying extra body fat can be beneficial," Ranchordas told the BBC.

"When we train athletes in the lab the first thing we do is measure their body composition – how much muscle mass they are carrying and how much fat mass they have around it.

"If you want to become a good cyclist, extra body fat is of no use whatsoever because that additional weight doesn't translate into performance. In boxing it can.

"If you're an extra 20 kilograms heavier – even if that weight is coming from fat – the opponent is going to feel your punch a lot more."

Ranchordas, who has worked with several professional boxers, says it's about finding the delicate balance between muscle, fat and fitness.

"If you are carrying extra body fat then your heart rate is going to be higher and you're going to have to use more energy to move around.

"If your ability to produce speed is great, your punching power is phenomenal and your fitness levels are very, very good – getting you to lose an extra 15 kilos of fat is probably not going to help.

"Ruiz is carrying a lot of body fat – but don't get me wrong he's carrying a lot of muscle mass at the same time. He's not just a fat blob.

"So how does he differ from an overweight guy down the street? That guy might weigh the same – but underneath the fat he's carrying nowhere near as much muscle."

Joshua's promoter Eddie Hearn, who also promotes Kiwi Joseph Parker, confirmed that the British star will trigger his rematch clause with Ruiz in an attempt to win back his titles.

Hearn says the rematch will likely take place in either November or December this year.