Technically they can, but only as a temporary fix
Coffee scrubs may lessen the appearance of cellulite, but the effect is short-lived at best. The scrubbing motion helps stimulate circulation, and the caffeine temporarily tightens the skin, making it look a little smoother. Other ingredients with caffeine, like green or black tea, can have the same result. Just don't be surprised when your skin goes back to normal eventually. (And, FYI, coffee grounds can clog your pipes, so you shouldn't use them in the shower unless you seal off the drain.)
You may experience longer-lasting success by pairing a caffeine product with one that contains retinoids (or finding a product with both); studies have shown that retinoids can boost collagen production in their skin. This, in turn, can help improve the look of cellulite. Choose a cream that has retinol or retinyl palmitate and you may notice a difference after about 12 weeks of use.
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However, even the best firming lotions don't address the real problem, which is fat. Cellulite happens when fat pushes up against the connective tissues that hold the skin to the muscles underneath, giving your flesh that dimply look. So in order to permanently reduce cellulite, you have to battle those fat deposits with exercise and a healthy diet. (Lean women can have cellulite, too, but being overweight can make it more noticeable—more fat means more bulge between the connective tissues.) There are also cosmetic procedures available that promise longer-term fixes for cellulite, but they'll cost you hundreds to thousands of dollars and can be painful.
Health’s medical editor, Roshini Rajapaksa, MD, is assistant professor of medicine at the NYU School of Medicine.