Specially for Girls... - You can gain weight in 10 days.

Being underweight can be a sign of illness or lack of nutrition. If you are underweight, you may not be getting enough vitamins and minerals in your diet. Even if you feel healthy, you may want to gain weight to look better, to fit into a favorite dress or even for medical reasons. With meal and snack planning, you can gain weight in 10 days.

Step 1

Eat more and more often. Take in at least three meals each day and a minimum of two large snacks. Increase your portions. Add one additional item to your typical breakfast. Eat a little bit more food during each meal. For example, add a little more cereal to your bowl, a thicker slice of bread for lunch and additional potatoes for dinner. If you want to gain even more weight in 10 days, eat a doughnut or a few granola bars after each meal and as a snack.

Step 2

Reach for the calories. Eat dense wheat, bran or rye breads and cereals, starchy vegetables such as potatoes, red beets, corn, squash and carrots, beans, nuts and dried fruits such as raisins, apricots and dates. 
Choose fruits that have higher calorie counts, such as apples, pears, pineapple and bananas. 
Choose heavy soups with beans or lentils. 
Experts consider one to two pounds of weight gain each week to be safe. 
To gain three pound in 10 days, you have to eat at least 1,000 extra calories each day.

Related Reading: Ways to Prevent Weight Gain While on Your Period

Step 3

Sprinkle on additional calories. Nuts, canola or olive oil, avocados, honey, butter, sour cream, wheat germ, protein powder, salad dressing, mayonnaise and peanut butter can be added to food to increase calorie intake.

Step 4

Reach for the soda, milk, fruit juice, milkshakes and smoothies. 
Skip diet soda and juices that do not contain real fruit. 
To gain the most weight, replace water with these high calorie options.

Step 5

Include a supplement between meals. This will not only quench your thirst, but will add calories.

Step 6

Lift weights. 
It may not seem logical to exercise while trying to gain weight, but exercise will help you to turn the added fat into muscle. 
Add weightlifting to your exercise routine at least three times per week.