Most of the time we turn on the TV and see an infomercial, they are certainly not trying to sell a product that increases your waist line. However there are situations that require you to bulk up and actually gain more fat, such as with body building and power training.
These situations make our bodies burn much more fuel than they normally would, and so require that we replenish that fuel we are using. To do this, our bodies will need many more calories and fat than would normally be consumed, thus giving us the need to find high-fat and high-protein foods. These foods would consist of things like peanut butter, beef, olive oil, nuts, fish, and anything that is rich in fat.
Gaining fat can actually help our bodies to stay healthy; the key knows how much fat to gain, and for what purpose. Simply eating unhealthy forms of fat without burning any calories is one of the most common causes for unwanted weight gain, while eating healthier forms of fat combined with exercise can be one of the healthiest lifestyles one can have.
To gain fat, we are obviously going to have to eat, and likely eat more than we typically would. However when we are eating all of these calories for the purpose of gaining fat, it is important that the type of fat we are consuming is good for us. The fats contained in junk food are the kind we want to avoid, the saturated fats that are solid at room temperature. The kinds that are generally good for us are olive oil, for example, and sunflower oil.
Now that you know what kind of fat to consume, you have to consume it with each meal. Instead of eating a protein bar for breakfast, eat a bagel topped with peanut butter alongside some eggs. Eggs are well-known as a muscle building food, and peanut butter is heavy with protein. Find creative ways to integrate these foods into your diet and before long you will be noticing significant gains.
If you change your diet to include more calories and protein, make sure that you are doing it consistently. Consistency is important to fat gain, and so it helps tremendously to stick to your new routine once you have found it.