No effect. It's as natural as sleeping and eating, which replenish your energy every day anyway
Well I agree with you that sex is natural. I personally haven't seen any compelling reasons to be abstinent. In fact, sex between my wife and I has gotten more frequent and fulfilling for both of us.
But while we humans naturally and helpfully enjoy sex and nourishment, our brains evolved in a world without processed foods and porn on demand. Look at the obesity crisis for a physical manifestation of how these new stimuli can hijack our brain circuitry. Damage from online porn is just as real, even if you can't visually see it.
But the hesitation and pushback is not surprising. You have obese people still gorging on double quarter pounders and smokers with lung disease still lighting up.
Change is really, really difficult and anyone claiming otherwise isn't being honest.