What is The True Secret Behind Saitama's Strength(One Punch Man)

[Ryuzaki Amv]

Hi everyone, I've been thinking about Saitama's power for quite a long now and he claims that he got that strength by training non-stop for 3 years and eating 3 meals a day to defeat enemies with a single punch, Now let's be realistic for a moment is that really true? What if his power is from those monsters that he killed during his multiple fights that he had against them, I'm not saying that his training didn't make him stronger, It comes from his training too but that cannot be the only reason for his strength that's what I know for sure.
That's my theory, it could be true/false but it is also a possibility .
Let's Hear Your Thoughts

 

[Will]

Lol, best training back story ever.
hose guys at the hero association might be right and he does have a god in him XP
Or we could use the whole thing where people who really wanted to be or do something actually got their wish granted through repetitive tasks or really wanting it, like how Saitama previously said he always wanted to be a cool hero that could kill any monster with a single punch
or

Spoiler

the hero hunter Garou who wanted to become a monster (which he does)

 

[Ryuzaki Amv]

Lol, best training back story ever.
hose guys at the hero association might be right and he does have a god in him XP
Or we could use the whole thing where people who really wanted to be or do something actually got their wish granted through repetitive tasks or really wanting it, like how Saitama previously said he always wanted to be a cool hero that could kill any monster with a single punch
or

Spoiler

the hero hunter Garou who wanted to become a monster (which he does)

Yes, that's how the world in One Punch man works he broke his limiter after years of intense workout and now he's the strongest