We are all dealing with the consequences of eating fast food, and not looking into what we consume, and that brings us to the problem of becoming obese or under-weight. 2/3rd’s of the US population is in the range from over-weight to obese, and the rest could be categorized as either not fat or skinny.

Source: stronglifts.com
This article is not going to be a specific diet plan that one needs to follow if they intend to gain weight or develop muscles, but a guideline that you can have to achieve your body goals.

How do you know if you are under-weight or over weight?

There is no 100 % sure way to label if someone is under or over, but a good estimation of a body can be calculated using BMI( Its called the body mass index ). Most of us probably already know about this, but never came to the realization that we might need it sometime in the future to predict our bodily health. 

The picture above is of a BMI chart using which you can check right now which category you fall under, but this is not a true estimation of ones health, but nevertheless an average human being should try to stay in the healthy zone.
So, once you know what category you fall under. If you fall under obese, look at this article to learn how you can lose weight and train to be fit.
There are certain ways you can gain weight. Some are healthier but require more effort, while others are unhealthy, but the results are fast.

Diet (food intake)

Eat in good proportions, and consume food that has nutrition, not just calories. Refer to the article
“Five most nutritious foods to eat”. 
Eat the foods mentioned in this article. They fulfill the body by taking care of your bodily deficiencies and energizes you. Forget the concept of having breakfast lunch and dinner. Get introduced to the concept of breaking those 3 meals into about 5-6 meals in a day, which has numerous benefits rather than disadvantages.

The faster way to gain weight with diet is to just eat junk food late at night, and go to sleep without burning up the carbs, and the starch and the fats. This will have bad effects on your body and could potentially put you at risk of having different diseases.
Eat foods rich in fiber so your immune and digestive system can work faster, which will help your body to process foods quicker.

  1. Drink protein shakes and have yogurt. Consume whole eggs everyday since they have good fats and are full of energy.
  2. Eat red meat every 2nd day so you can have whole lots of protein which is essential for making muscle.
  3. Eat rice. They are high in carbohydrates and low in fat which helps in gaining healthier fat.
  4. Eat potatoes and foods that have starch.

Exercise and Activity

There are a couple of exercises that you can collectively do in order to turn your body fat into muscles and turn saggy parts of your body into firm and strong attractive looking “accessories”.

  •        Pushups

They are a great way to focus fat burning and muscle strengthening on biceps and chest. The most effective way to do pushup is to go all way in almost touch the ground and, come back to the same height you started from.
  •        Squats

Squats are targeted towards strengthening of the legs and thighs and doing them regularly will help make your lower body stronger. You will be able to lift heavier weights through your legs.

  •        Crunches

Crunches are perfect for the abdominal, and it is one of the most effective exercise to get rid of big belly. The perfect way to do crunches is to put something heavy on the foot so the whole body doesn’t lift upwards while you are going backward and forward performing the crunches.
While you do all these exercises, it is best to time your meals properly, and burn off most of the calories you consumed before you go to sleep. It will make you feel lighter plus your sleep will be better as well.

So, to sum it up:

  •       Eat more calories and more meals per day (increase intake of calories by 20%. An average human being needs about 1500 calories, so a skinny person should consume more than 2000 calories or even more depending on how quickly they want to achieve their goal, but its recommended to go slow so the results are in balance with how the rest of the body deals with it.
  •       Hit the gym, or do the exercises mentioned above in excess so that the calories you have consumed are not making your body saggy but instead are getting converted into muscle, which is healthy and doesn’t have any drawbacks other than that you might have to buy all new wardrobe.
  •       Drink smoothies, and protein shakes and start taking multivitamins so all the bodily needs are fulfilled.

Note: Genetics play an important role in determining whether you are under or overweight, and it can be harder if you are on the downside of it. But you are sure to get results if you follow all the tips, and follow them regularly.