Multivitamins

• Standard multivitamins are inexpensive and can be found in most pharmacies.vitamin image by Dmitry Sosenushkin from Fotolia.com
  
  Multivitamins can be found anywhere and it's the first step when looking to gain weight. Finding a multivitamin that has a healthy dose of iron and magnesium is a good place to start. Along with the multivitamin, a high caloric diet filled with protein and healthy fats, such as fish and lean meats, will be the combination for healthy weight gain.
  
  

Iron

• Find iron in food such as shrimp and lean red meats.Succulent Steak and Shrimp on the Barbecue image by Andy Dean from Fotolia.com
  
  Iron plays a large role in supplying your body with the needed proteins and enzymes to maintain good health. If you are not in good health, gaining weight will be nearly impossible. Iron deficiency can actually cause growth problems, in turn, hindering weight gain. Moreover, one side effect of taking most generic iron supplements is weight gain.
  
  

Magnesium

• Dark leafy greens such as spinach and kale are great sources of magnesium.Spinach Crop image by Karin Lau from Fotolia.com
  
  Magnesium is extremely beneficial when gaining weight as it plays a part in your energy production. It also aids enzymes by triggering them to release essential nutrients into your body. Magnesium is also found in many foods used to treat extreme malnutrition.
  
  

Protein and Fats

• Mixed nuts are a great source of vitamins, healthy fat and protein.mixed nuts image by Joyce Wilkes from Fotolia.com
  
  While taking a multivitamin, partner it with a high-protein, healthy fat diet. To promote faster weight gain, lean meats and fats, such as the fats found in nuts, are perfect for this diet. Even if you're not taking supplements, you can still get the same vitamins in everyday food. For example, almonds are rich in magnesium, while sesame seeds provide a high amount of iron.
  
  

Caloric Intake

• Junk food may make you gain weight, but it's extremely unhealthy.french fries image by Wimbledon from Fotolia.com
  
  Most average males should be ingesting between 2,000 to 2,500 calories, and women between 1,500 to 2,000 daily. Adding 500+ healthy calories to your normal caloric intake that are high in magnesium, iron and the other listed nutrients, contributes greatly to weight gain. Avoid junk food as it does nothing in terms of healthy weight gain and usually hinders your efforts rather then helping them.