In fact, for his rugby playing future, he needs to put on some weight. But in doing so he may lose one of the main strings to his bow.
Dickson is an up and coming lock-cum-blindside flanker.
Today he will start on the side of the scrum for Otago against Taranaki, following a couple of impressive games at lock for the blue and golds to start the season.
The 20-year-old was all over the paddock in those first two games and scored a richly deserved try in the match against Hawkes Bay.
Dickson is quick around the field. There is no doubt about that.
But that speed comes from being somewhat lighter than most locks running around.
Dickson weighs in about 107kg, and he says putting on weight is a major priority.
''Ideally, I would like to be something like 115kg. That's what most super rugby locks are,'' he said.
''When I get a chance I want to put some weight on. I'd like to think I can put the weight on. I'm eating as much food as I can. Counting the calories.
''I'm lucky with the body type I am, I can afford to eat a lot. But when you do a lot of running, like you do at training or at a game, then you lose weight.''
Dickson is piling into the carbohydrates and high-energy foods to try to build muscle.
But therein is the issue.
Dickson's game is based around his speed around the paddock. He needs to gain some bulk to be more of a physical presence in the game. Getting bigger may cut down his speed around the paddock, although it should help him take the knocks.
''I've always been this shape, so I don't really know if it will help me feel any different from the game if I get a bit heavier.''
''At the end of a day, it is more of a mental thing. You get near the end of a game and you have to push yourself to keep going, making the hits, getting up off the ground.''
He weighed himself every day, sometimes both morning and night.
Whatever his weight, Dickson is a very promising player.
Not 21 until November, his athletic ability and huge engine are real assets for Otago. Statistics and skin folds may be a big thing in rugby these days but it is still about performances on the field and Dickson is making people notice.
He was initially schooled at Mt Aspiring College before heading to Otago Boys' High School for his final two years of education.
A member of the first XV, he was selected for the New Zealand schools side in 2012 but missed out on playing, because of a broken thumb.
He made the New Zealand Colts side last year, and the next step appears to be a Highlanders contract.
''That is what I want to do. Ultimately, that is what every rugby player at this stage wants to do. But I just have to do what I can for Otago.''
In his last year of a personal training course, he has not signed anything with the Highlanders and Dickson knows all he can do is perform at his best for Otago.
Playing in a winning team also helps land contracts and Otago, and Taranaki for that matter, need to start doing that tonight.
Both teams have clocked up two losses and need to get their campaigns going.
Taranaki made a late change yesterday. First five-eighth Marty McKenzie is out with a hip injury, so Beauden Barrett comes in to 10, Kurt Baker goes to fullback and Jackson Ormond goes to the wing. Latu Vaeno comes on to the bench.
Otago has lock Tom Franklin and No 8 Charlie O'Connell back and they need to lead a more physical effort.
There is no hiding the fact Otago has a tough opening to its season, but it must continue to head upwards following an improved showing last week.
The game will be refereed by former first-class player Jamie Nutbrown, who has enjoyed a quick rise up the refereeing ranks.
Heavy rain is forecast for New Plymouth today.
ITM Cup Otago v Taranaki
New Plymouth, today, 5.35pm
Otago: Peter Breen, Matt Faddes, Jayden Spence, Tei Walden, Jack Wilson, Fletcher Smith, Josh Renton, Charlie O'Connell, Theo Commissaris, Josh Dickson, Tom Franklin, Blair Tweed, Hisa Sasagi, Liam Coltman (captain), Craig Millar. Reserves: Sam Anderson-Heather, Donald Brighouse, Aki Seiuli, Mika Mafi, Naulia Dawai, Kaide Whiting, Michael Collins, Tony Ensor.
Taranaki: Kurt Baker, Codey Rei, Seta Tamanivalu, Charlie Ngatai (captain), Jackson Ormond, Beauden Barrett, Te Toiroa Tahuiorangi, Iopu Iopu-Aso, Berny Hall, Mitchell Crosswell, Blade Thomson, Mitchell Brown, Ryan Cocker, Sione Lea, Mitchell Graham. Reserves: Caleb Mawson, Reuben O'Neill, Jared Profit, Riki Hoeata, Toa Halafihi, Kylem O'Donnell, Sean Wainui, Latu Vaeno.
Referee: Jamie Nutbrown (Canterbury)
