Avocados are packed with nutrients like fiber and vitamin K, but they're also much higher in calories than most other fruits. While most plant foods have almost no fat, avocados have significant levels of monounsaturated fats, which are considered healthy fats; however, gram for gram, fat has more than double the calories of protein or carbohydrates. To avoid calorie overload, stick with the suggested serving size of one-fifth of an avocado.
On average, the flesh of one medium California avocado contains about 227 calories. If you only eat one-fifth of the fruit, you'll consume about 45 calories. Eat half an avocado and you'll consume about 114 calories. Although avocados are calorie-rich compared to other fruits, they still have fewer calories than fatty condiments like mayonnaise, which contains 94 calories in just 1 tablespoon. Therefore, you'll significantly reduce your calories -- and gain more nutritional benefits -- by replacing the mayonnaise on your sandwich with avocado.