• Avocado

Avocados are rich in monounsaturated fatty acids plus they have vitamin K, potassium, and fiber. One avocado has more than 200 calories so it's a good way to add extra calories without sacrificing good nutrition.

Add avocado slices to your sandwiches or make guacamole and serve with baked tortilla chips. You can also add guacamole to soft shell tacos or burritos.

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• Granola

Make your own granola with any combination of dry whole grain cereals, nuts, seeds and dried fruits. Store your granola in an airtight container and serve it for breakfast. 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.

• Salmon and Oily Fish

Like red meat, salmon and oily fish are excellent sources of protein and important healthy fats.

Out of all the nutrients that salmon and oily fish provide, omega-3 fatty acids are among the most significant and well known.

Omega-3 fatty acids are very important, providing numerous benefits for your health and also fighting disease.

Just one 6-ounce (170-gram) fillet of salmon provides around 350 calories and 4 grams of omega-3 fats. It also provides 34 grams of high-quality protein, helping you build muscle or gain weight.

• Whole-Grain Bread

Whole-grain loaves of bread are another good carb source to help you gain weight.

You can make some very simple, high-calorie and well-balanced meals by combining bread with protein sources such as eggs, meat, and cheese.