What diet change produces the most effective results in reducing BF%?

I know reducing your calories overall is important but what specific nutrient has the biggest effect.

Just curious as to what people think, I always thought carb manipulation was most effective but I'm surprised at how many people think that it's cutting saturated fats.
Cutting Carbs
Cutting Saturated Fat
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What diet change produces the most effective results in reducing BF%?
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