A calorie deficit occurs when you consume fewer calories than your body needs to maintain its current weight. This can happen through reducing food intake, increasing physical activity, or a combination of both. When in a calorie deficit, the body starts to use stored fat for energy, which can lead to weight loss over time. To achieve a calorie deficit, individuals often track their daily calorie intake and expenditure. Tools like fitness apps or calorie counters can help monitor this balance. It's important to create a sustainable deficit to promote healthy weight loss without compromising overall well-being.