Breads and cereals are a good source of complex carbohydrates your body needs for energy. Bagels just happen to be extra calorie-dense. While one slice of bread has about 70 calories, one small 3-inch bagel has over 150 calories.
Top your bagel with cream cheese and some 100-percent fruit spread for a high calorie (but healthy) snack.
Pasta is another calorie-dense source of carbohydrates so it can serve as the base of a healthy and high calorie meal (one cup of cooked spaghetti noodles has 220 calories).
Top your pasta with lycopene-rich marinara sauce and add a quarter cup of shredded cheese for more calories and calcium. If you're pressed for time and money, you can try my ramen noodle makeover.
Give yourself a quick calorie boost by eating dried fruits instead of fresh fruits. They have less volume than their fresh counterparts, so one half-cup of raisins has more calories (over 200) than a full cup of fresh grapes (about 60) and still offers good nutrition.
Raisins are probably the most popular dried fruit in your local grocery store, but you can also find dried berries, apricots, cranberries, and even tropical fruits.
Healthy Fats and Oils
Adding extra fat to your food is an easy way to add calories, but you want to be sure to choose fats and oils that are good for you.
Olive oil is rich in healthy monounsaturated fatty acids and can add calories and flavor to pasta, bread, or vegetables. Canola oil is a good source of omega and monounsaturated fats and it makes a terrific all-purpose cooking oil. Walnut and grape seed oils are lighter in flavor and perfect for topping salads.
Avocados are rich in monounsaturated fatty acids plus vitamin K, potassium and fiber. One avocado has more than 200 calories.
Nuts and Seeds
Nuts and seeds contain polyunsaturated fats that add healthy calories to your diet. Brazil nuts, almonds, walnuts, pecans, cashews, sunflower seeds, flax seeds and pumpkin seeds are all good for you.
Eat roasted nuts and seeds by the handful or slather some nut butter on an apple for a nutrient-dense and calorie-dense snack.
Pack some granola into small plastic containers that you can take with you on a busy day. For more flavor and calories, you can add chocolate chunks or peanut butter chips.
Choose 100-percent fruit juice instead of sugary sodas and energy drinks. Look out for fruit-flavored drinks that are mostly sugar or high-fructose corn syrup -- they just don't have the nutritional value of 100-percent fruit juices.
Vegetable juice (low-sodium is best) tends to be lower in calories, but still contains vitamins and minerals.
Eat one or two protein bars in addition to your regular diet -- they probably won't help you gain weight if you use them to replace other foods.