The second driver is dietary, and it catches a lot of lifters off guard. Whey protein — the supplement most gym-goers use daily — has been shown in multiple studies to spike insulin-like growth factor 1 (IGF-1). Elevated IGF-1 stimulates the skin's oil glands to produce more sebum, which means more clogged pores.
Highly processed foods — high-glycaemic carbs, sugary drinks, fast food — have a similar effect through insulin spikes. The combination of training stress, dietary IGF-1 triggers, and hormonal activity creates a hormonal environment that's genuinely hostile to clear skin.
This explains why a lot of lifters find their acne is worst on the chest, back, jawline, and upper back — areas with the highest concentration of oil glands, and the areas most affected by systemic hormonal changes.