Some methods of gaining weight can have severe short- and long-term effects on health. This poses a challenge for people needing to gain weight and for those who are at a healthy weight but wish to build muscle.
This article explains how to determine whether a person is underweight. It also provides tips for gaining weight safely and healthfully, including what to avoid while trying to put on weight.
What is the definition of underweight?
A BMI can indicate whether someone has a healthy weight.
Using body mass index (BMI) is a common way to determine whether or not an individual is within a healthy weight range. People can calculate their BMI using their height and weight.
A person with a BMI of 18.5–24.9 will be within the healthy range. According to guidelines, a person with a BMI of less than 18.5 is underweight and may need to gain weight for their health. However, in some cases, it is possible for an individual to have a low BMI but remain healthy.
There are also some factors that the BMI does not take into account, such as muscle mass. This can lead to a healthy person having a weight that is outside of the ideal range. For instance, they may have a very high BMI due to being muscular, rather than because they have a high proportion of body fat.
In general, a person's BMI provides a reasonable indication of whether or not they are a healthy weight.
You can determine your BMI using one of our BMI calculators or charts.
What are the risks of being underweight?
There are many health risks relating to low body weight. In many cases, being underweight is due to a poor diet. This can cause malnutrition, which has risks of its own. For example, a deficiency in vitamin D can have a negative impact on bone health.
A person needs to consume a sufficient amount of calories each day for the body to function correctly. A diet too low in calories can cause:
- hair and skin issues
Being underweight can also lead to:
- a weakened immune system
- an eating disorder
- developmental issues
- increased risk of infection
How to gain weight healthily
Using a calorie tracking app may help when trying to gain weight.
Putting on weight may be necessary for a person who is underweight. It may also be a measurable goal for someone who is aiming to build muscle.
In general, consuming more calories than the body burns will result in weight gain. The calorie intake necessary to achieve this will vary from person to person.
As a guide, consuming 300–500 calories more than the body burns on a daily basis is usually sufficient for steady weight gain. For more rapid weight gain, a person may need to consume up to 1,000 calories more per day.
Many people inaccurately estimate the number of calories they consume each day. It can be useful to keep track of daily calorie intake over a period of 2–3 weeks. This can help a person understand how to adjust their diet to gain weight at a sufficient pace. There are several apps available online that can assist with calorie tracking.
People who are trying to gain weight should also be mindful of the types of food they are consuming. For example, eating foods that are high in sugar is an easy way of increasing calorie intake, but it can also increase a person's risk of developing type 2 diabetes.
General tips for gaining weight safely
The following tips can help a person gain weight quickly and safely:
Eat three to five meals a day
Eating at least three meals a day can make it easier to increase calorie intake. Snacking between meals can also help to increase the number of calories in the diet.
Weight training at least three times a week is essential to healthy weight gain. This will aid in gaining and maintaining lean muscle mass.
To continue gaining lean body mass, a person will need to vary and develop their workouts by increasing either the weight they lift or the number of reps or sets.
Compound movements are one way in which a person can build muscle effectively. These include weight lifts that involve multiple muscle groups, such as deadlifts, squats, and bench presses.
People who work out regularly must pay attention to their calorie intake to ensure that they are providing their body with sufficient fuel.
Eat enough protein
A diet with the right amount of protein will support muscle growth. In combination with regular weight training, consuming 0.8–2.0 grams of protein per kilogram of body weight will increase a person's muscle mass. This is essential to healthy weight gain.
Foods high in protein include eggs, meats, fish, nuts, and legumes.
Eat meals with fibrous carbohydrates and healthful fats
Including foods rich in fibrous carbohydrates and healthful fats in every meal will help to increase the number of both calories and nutrients in the diet.
These foods provide an essential energy source to maintain a regular exercise regime, and to support muscle growth. People should use whole-food sources of carbohydrates, such as brown rice and beans, rather than refined and processed sources.
Distinguishing between healthful and unhealthful fats is vital. Healthful fats are generally monounsaturated or polyunsaturated fats, which occur in foods such as nuts, avocado, vegetable oils, and fish.
Unhealthful fats include saturated fats and trans fats. A healthful diet should limit saturated fats and avoid added trans fats. These types of fats are found in fried and baked foods as well as in fatty meats such as beef, pork, and lamb.
Drink high-calorie smoothies or shakes
People with a small appetite may find a high-calorie shake or smoothie more appealing than a large meal. These provide nutrient-dense calories without making a person feel overly full.
Suitable smoothies can include the following ingredients:
- nut butter
- greens, such as spinach
Seek help where needed
Health and fitness professionals provide motivation and useful advice for developing diet and exercise plans to support healthy weight gain.
Similarly, a registered dietitian will be able to provide meal plans to increase calorie intake. Also, they can help to ensure that a person is gaining weight safely.
Things to avoid when gaining weight
Cardiovascular exercise is important for ensuring overall health.
When attempting to gain weight, a person should be careful to avoid the following:
Insufficient cardiovascular exercise
Some people stop doing cardiovascular exercise when they are trying to gain weight, but it is essential for maintaining a healthy heart, lungs, and brain. Running, swimming, and cycling are all good ways to get cardiovascular exercise.
People keen to gain weight can try restricting cardiovascular exercise to around 20 minutes, three times a week, rather than avoiding it entirely.
A diet low in vegetables
Many vegetables are filling but have a low calorie content. However, it is crucial not to exclude them from the diet for the sake of weight gain. Vegetables are a vital source of vitamins and minerals and not eating enough of them may cause malnutrition.
Giving up too quickly
Safe weight gain can require patience and determination. It is not always possible to see results immediately. Everyone is different, and it may take longer for some people than for others.
Being underweight can cause health problems, so some people may need to gain weight. Although it is common to want to gain weight quickly, it is also important to do it safely.
People who are trying to put on weight should still aim to eat a balanced diet, weight train, and get enough cardiovascular exercise.