Empty calories are the calories in food that contains energy but no nutrients — fuel without the micronutrient payload. Sugary drinks, sweets, alcohol, and many fried snacks deliver kilojoules or kilocalories with negligible vitamins, minerals, fibre, or protein: they fill the energy budget while contributing nothing to the nutrient budget. The concept is the core of the nutrient-density argument — that foods should be judged not just by energy but by nutrients per calorie. Diets high in empty calories drive the paradox of modern malnutrition: overweight yet deficient, overfed and undernourished. Public-health policy targets them directly — sugary-drink taxes, junk-food advertising curbs — because they are the easiest calories to cut without nutritional cost. The phrase is a dieter’s shorthand for energy that gives nothing back.