Struggling As A Skinny Guy
In our society being thin or skinny is looked as someone being “blessed” or having “great genes”. For many guys, though, this could be both a blessing and a curse.
While most people have the problem of excess body fat from poor dieting choices, skinny guys have the problem of not getting enough calories in a day.
This problem has led to many people ruining their bodies with diets high in excess calories, resulting in the skinny fat epidemic (see How to Properly Gain Muscle).
So if we’re eating the excess calories we need and are still lifting weights regularly without any kind of impressive results, it probably isn’t what we’re doing, but how we’re doing it.

Why Some People Have Trouble Gaining Muscle
The first fitness program I bought online was flawed because I didn’t know enough about nutrition. Nutrition is responsible for 80% of the results you achieve in the gym.
Often, when we don’t have meal plans, we choose foods based on how our moods change throughout the day.
These are the 3 reasons why someone with higher than average metabolism would have trouble putting on any kind of significant muscle:

Not Enough Calories:
To gain muscle, you must consume more calories than your body burns, which puts you in a caloric surplus. The number of calories required depends on your daily activity level—the more active you are, the higher your caloric needs for muscle growth.
With sufficient expenditure, this can result in a caloric deficit, which, if prolonged, can lead to muscle loss.
With cloud-based food-tracking software now available, personal trainers can connect with their clients and adjust their meals daily to calculate the best portions for adding muscle size.
The healthier option for adding calories to meals is to use a multi-chain triglyceride, such as coconut oil, rather than relying on fast food.

Too Much Work In The Gym:
If gaining weight has always been a problem, you should check how much time you spend in the gym. Any workout past the first hour becomes unproductive and can even have the opposite effect on your muscle growth.
Guys with the ectomorph or ecto-mesomorph physique often have difficulty building muscle due to their faster-than-normal metabolisms.
To maintain as much muscle as possible, ectomorphs should be exercising within 45 minutes and keep excessive cardio to a minimum.
Healthy amounts of cardio can help prevent excess calories from being stored as fat, but can make weight gain more difficult for naturally skinny guys.

Keeping A Negative Nitrogen Balance
Each day, our bodies rid themselves of millions of dead cells, which are eventually replaced and rebuilt from new sources of amino acids we consume (protein).
The best way for ectomorphs to gain muscle is to consume enough protein each day to maintain a positive nitrogen balance. Having a high metabolism in this sense is a curse, as it makes it more difficult to maintain a consistent positive nitrogen balance throughout the day.
The Wrap Up
Gaining muscle will be slower for hard gainers, such as ectomorphs or mesomorphs, which is why you have focused more on consuming larger, high-quality meals during feeding times. This is even more important on workout days: you need to consume more energy than your activity levels require to see any muscle growth. Doing this over a long period will gradually add more size to your frame.
What else do you want to know?