In both the movies and comics Cap gains his peak human strength via the supersoldier serum and a does of vita rays, resulting in the rapid development of his super buff body:

Maximum buff-itude

While the most obvious real world analogue would be the use of steroids, these would still require that the person taking them train extensively and significantly increase their protein intake in order to gain muscle mass. While there are frequent scenes of Steve training in both mediums I've yet to see any scenes of him eating a 12-egg omelette or downing protein shakes. Are there any in-world explanations that would account for the increased muscle mass? Extra-dimensional energy conversion?

enter image description here

  • 6
    In the movie, doesn't he go into the machine all un-buff and come out buff?
    – phantom42
    Commented Dec 10, 2014 at 19:32
  • 2
    are you asking how he initially gained the muscle mass, or how much he has to eat to maintain the muscle mass? or what did his body use to create all of that extra muscles?
    – Himarm
    Commented Dec 10, 2014 at 19:35
  • Just an FYI, protein is not required to build muscle mass, nor does it build muscle. Regardless of how much you work out/weigh/etc having extra intake of protein is not necessary. Roger's exposure to the super soldier serum is what gives him his strength and physique and as stated in the movie, with this, he also gains a wolverine esque healing factor(though not nearly as advanced). This healing factor coupled with his metabolism is what allows him to keep his figure so to speak.
    – Robert
    Commented Dec 10, 2014 at 19:36
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    id assume he does eat quite alot, however i also believe his body is able to use more of what he eats with less waste as hes now more efficient. however we can probably assume that a typical male that is very inshape/large muscles, and is regularly expending energy either working out, or saving the day is eating more then 2000 calories a day, id hazzard hes eating closer to 5k a day maybe more or less depending on what he did that day, example extensive healing probably makes him very hungery ect.
    – Himarm
    Commented Dec 10, 2014 at 19:40
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    The same place the Hulk gets his...
    – Schwern
    Commented Dec 10, 2014 at 20:18

4 Answers 4


CAVEAT: I'm going to use the movies as reference, because I haven't read the comics. Feel free to fill in with canon.

For his initial bulking up, we can assume the machine provided him with the extra mass. This avoids the Bruce Banner / Hulk problem.

For maintenance, Captain America's metabolism has been altered in who knows what way, and it's much faster. Also, he has some sort of super-liver because he can't get drunk.

Steve Rogers: Dr. Erskine said that the serum wouldn't just effect my muscles, it would effect my cells. Create a protective system of regeneration and healing. Which means, um, I can't get drunk. Did you know that?

Peggy Carter: Your metabolism burns four times faster than the average person. He thought it could be one of the side effects.

Cap probably does need to eat more, but his altered metabolism might allow his body to transform food more efficiently. Normal people get fat from eating the wrong foods because of the way our metabolism works due to millions of years of evolution optimized for food scarcity. Normal people need to work out to gain muscle because again, evolution has optimized us to be efficient with our calories. Don't use those muscles? Don't put the calories into maintaining them. Cap's body has been altered and it's Stark, not evolution, who's in charge now.

Our bodies can already manufacture most of the vitamins and proteins we need, it's only certain ones we need to ingest. Perhaps Cap doesn't even need those anymore and can scarf mineral enriched candy bars all day knowing his body will use the minerals and sugars to turn it into anything he needs.

I think we don't see Cap eating a ton of food (do we ever see him eating?) because it doesn't fit the movie's tone. Most superhero films have an early scene showing a mundane down side to their powers and it's usually a bit goofy. The Flash usually gets a scene where he's stuffing his face. Steve Rogers is presented with more dignity. The "I can't get drunk" scene is his equivalent to The Flash emptying the fridge.

The Abridged Script from The Editing Room hits the nail right on the head.


Zo, you vish to fight zee Nazis?


Yes sir. I'm willing to spend hours at the gym, eat a ton of that disgusting weight gain powder, and work my ass off if that's what it takes!


Ha ha, zilly boy! Ve have drugs for you!


Wait, the Marvel superhero meant to most perfectly embody the American ideal got his powers not from hard work, not even from luck, but from cheating by using what are basically blue steroids?


  • Although it isn't backed up with any canonical references I'll go with this answer as it strikes me as sufficiently conforming to existing in-world explanations.
    – Dre
    Commented Dec 14, 2014 at 13:08
  • Technically, there's a scene within the credits of The Avengers where they're at the shawarma joint that Stark mentions, but admittedly, none of them are "stuffing their faces," despite both Cap and Bruce, at least, probably having the most reason to.
    – Shauna
    Commented Dec 16, 2014 at 19:31

My current theory is that the super soldier serum and vita rays bestowed him with a hyper-efficient metabolism and healing ability. This enables him to actually eat himself (in the form of creamsicles), ingesting the calories whilst simultaneously healing from the self-inflicted injuries; in effect creating an autophagic self-sustaining calorific feedback loop:

enter image description here

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    That doesn't look like a creamsicle that he's eating.
    – phantom42
    Commented Dec 10, 2014 at 20:20
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    It looks like a popsicle, but with more o.
    – Mr Lister
    Commented Sep 27, 2015 at 11:15

Cap downing several raw eggs in a glass Rocky style after doing one arm pushups and reading the paper lol is it possible he got this from watchimg Rocky after being defrosted???

Cap appears to restrain himself unlike wolverine who is more gluttonous with his eating which means he probably tries eating a nutrutious diet so he can be in top shape to fight the worlds enemiesenter image description here

There is another part where they go back for meat night and Cap says hes stuffed and has to get up at 5 a.m. to run just to burn it off, then wolverine says "when do you not get up at 5 a.m. just to run" which leads me to believe in oeace time he adheres to a strict regimen of morning training and good diet. I have scene in the comics of him training with weights, hitting the heavy bag and a custom made gymnastic gym but with bars in all crazy direction

Im a big Cap fan and former powerlifter and strongman and I have read alot of Cap comics and thre is evidence he trains as regularly as he can when he can but because of his schedule he probably has to get workouts when he can and wherever ge can

  • Superheroes eating! Yay!
    – Dre
    Commented Jan 30, 2015 at 9:43

As Steve Rogers metabolism is faster, his protein synthesis probably is too. He must eat a lot, and even with a regular intake of proteins/fats/carbs for his metabolism, it is much higher than a normal person metabolism. So, even with a regular intake, he'd be bigger than even a person who trains a lot/eats a lot

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