Sugar by itself does not cause acne. But steep insulin spikes increase the production of skin oils, which clog follicles and worsen skin complexion.
However, sugar and other foods with a high glycaemic index have been shown to exacerbate problem skin. Foods with a high glycaemic index (think refined carbohydrates and “fast food” - fizzy drinks, sweets, white bread, white rice and any highly processed food) are rapidly absorbed by the body, causing a rise in blood glucose (sugar), which in turn causes a rise in insulin levels. Steep insulin spikes increase the production of skin oils and contribute to the clogging of follicles, which can, in turn, worsen skin
complexion.