Although being lean can often be healthy, being underweight can be a concern if it's the result of poor nutrition or if you are pregnant or have other health concerns.

So, if you're underweight, see your doctor or dietitian for an evaluation. Together, you can plan how to meet your goal weight.

 Why is gaining weight important?

While about 74 percent of adults in the U.S. are either overweight or obese, there are also many people with the opposite problem of being underweight.

Some individuals may be naturally underweight due to genetics or a fast metabolism. Being underweight may also be indicative of poor nutrition or underlying health conditions.

Additionally, many people who are not clinically underweight may still want to gain some muscle and put on weight for other reasons.

Whether you’re clinically underweight or simply struggling to gain muscle weight, the main principles are the same.

Here are some healthy ways to gain weight when you're underweight:

Exercise

Exercise, especially strength training, can help you gain weight by building up your muscles. Exercise may also stimulate your appetite.

Have an occasional treat 

Even when you're underweight, be mindful of excess sugar and fat. An occasional slice of pie with ice cream is OK.

But most treats should be healthy and provide nutrients in addition to calories. Bran muffins, yogurt, and granola bars are good choices.

Make every bite count

Snack on nuts, peanut butter, cheese, dried fruits, and avocados. Have a bedtime snack, such as a peanut butter and jelly sandwich, or a wrap sandwich with avocado, sliced vegetables, and lean meat or cheese.

Top it off 

Add extras to your dishes for more calories — such as cheese in casseroles and scrambled eggs, and fat-free dried milk in soups and stews.

Choose nutrient-rich foods

As part of an overall healthy diet, choose whole-grain bread, pasta, and cereals; fruits and vegetables; dairy products; lean protein sources; and nuts and seeds.

Try smoothies and shakes 

Don't fill up on diet soda, coffee, and other drinks with few calories and little nutritional value.

Instead, drink smoothies or healthy shakes made with milk and fresh or frozen fruit, and sprinkle in some ground flaxseed.

In some cases, a liquid meal replacement may be recommended.

Watch when you drink

Some people find that drinking fluids before meals blunts their appetite. In that case, it may be better to sip higher-calorie beverages along with a meal or snack.

For others, drinking 30 minutes after a meal, not with it, may work.

Eat more frequently

When you're underweight, you may feel full faster. Eat five to six smaller meals during the day rather than two or three large meals.

like morning snacks or evening snacks; that can also help increase body weight. 

Consumption of energy-rich foods

Make sure to eat, energy-dense foods like nuts including almonds, walnuts, and peanuts, and dried fruits including raisins or prunes.

And dark chocolate, high-fat dairy foods like condensed milk, full-fat cream, cheese, and milk, veggies like potatoes and yams, etc.

‍Eat Pattern

Whenever there is a choice in a mixed platter, prefer eating your carb-rich or calorie-rich diet and protein-rich diet first and the veggies later.

This commissions the digestive system to digest carbs and protein ahead of fats, vitamins, or minerals.

Such a trend in digestion aids in the early burning of the digested calories and gradually you end up eating again.

Conclusion

There are many reasons for wanting to gain weight.

It’s important to do so by eating nutritionally-dense foods and building lean muscle mass.

At the end of the day, changing your weight is a marathon, not a sprint. It can take a long time, and you need to be consistent if you want to succeed in the long run.

If you’re struggling to gain weight despite trying the strategies discussed above, it’s important to talk with a doctor or dietitian.

A dietitian can help you employ eating strategies that may help you reach your goal.