How to Gain Weight Safely

Often, when we talk about our health, we talk about losing weight. But sometimes, there’s a need to actually put on weight. This might seem counterintuitive, but there are several scenarios where your doctor might ask for you to gain weight, no matter your age or sex.

Besides the “why,” there is also the “how.” When you have to gain weight, you still want to use a healthy approach, not just add a bunch of high-sugar and high-fat items to your diet. While that will certainly add weight, that approach is not necessarily the best for your body.

We talked to pediatrician Ellen Rome, MD, and registered dietitian Devon Peart, RD, MHSc, about why your doctor might ask you to add weight and ways to do it safely — both for children and adults.

Why your doctor might ask you to gain weight

Whether you’re an adult or a child/adolescent, there are several reasons why your doctor might advise you to gain weight.

Below a healthy body weight

Peart says doctors will look for markers of healthy body weight and if, based on evidence, they decide you’re underweight, they may advise you to gain weight. “While body mass index (BMI) may have a lot of drawbacks, it can help a doctor see if someone is at a low weight that’s unhealthy,” she says. “The concern would be whether you are getting enough vitamins, minerals and energy (calories) for your body and your immune system to function well.”

Fighting illness

Another reason, according to Dr. Rome, is that you’re fighting an acute or chronic illness. This could be for an adult or child. “It could be something like inflammatory bowel disease where the patient has lost a lot of weight,” she says. “Or it could be a cancer patient who needs to build some strength before beginning treatment.”

Such a need can also be necessary after major surgery, whether that’s a dental surgery that interferes with your ability to eat or another operation that resulted in weight loss. “After something like that, where a person hasn’t been able to maintain a normal diet, they’re not at their usual body weight and they’ll need to gain it back,” notes Peart.

It’s also possible that various treatments can affect appetite or even the taste of food, she adds. “Medication can cause food to taste metallic and so you don’t eat as much because it just doesn’t taste very good.”

Avoidant/restrictive food intake disorder

While food-restrictive disorders like anorexia nervosa are among the reasons someone might need to add weight, a newly recognized disorder known as avoidant/restrictive food intake disorder (ARFID) is a reason children may need to add weight, according to Dr. Rome.

“These children fall into a few different groups, and they can be in more than one group,” she continues.

These groups include:

• Children who have limited intake because they’re picky eaters or are just not interested in food.
• Children who perceive food as scary or dangerous. “For example,” Dr. Rome says, “if a child chokes or gets sick from a specific food, they might want to avoid that food.”
• Children who have other conditions that cause them to avoid food, like chronic abdominal pain, losing their sense of smell and taste from COVID-19, or loss of appetite from other illnesses such as infectious mononucleosis.

“We’re learning more and more about how to help the children who are diagnosed with ARFID,” she adds.

How to gain weight safely

When gaining weight is your goal, it’s important to do so in a healthy, nutritious way that doesn’t cause any harm to your body or long-term health. And that’s not as difficult as you might think.

Healthy fats for kids

Proteins, fats and carbs are the fuel your body needs, especially in kids, and it’s important to get that balance right. The problem, says Dr. Rome, is the way fat is sometimes treated. “A parent may be told to cut back on fats for their diet but you can’t apply that to a kid’s diet,” she says. “From early adolescence through age 26, their fat intake should be about 50 to 90 grams of fat a day.”

Food like avocados and hummus are great sources of these fats that can help kids gain that weight safely. Using avocados to make guacamole is a great way to make it more appealing for kids. Dr. Rome says it’s also OK to occasionally indulge in some ice cream — in moderation.

Choose calorie-dense foods

It’s similar for adults. Peart says to focus on finding that balance in consuming more calorie-dense foods that still hold some nutritional value. “It’s not just about calories. You might think that eating a lot of candy would add calories but it wouldn’t be in a healthy way,” she says. “Nor do you want to fill up on lower-calorie foods like popcorn.”

Instead, she also recommends the avocado as one go-to snack. “It’s heart-healthy and has healthy fat,” she points out. Other suggestions include:

• Cheese.
• Nuts.
• Nut butter (peanut butter, almond butter).
• Dried fruits.

“These foods help bring more calories to your meals or snacks,” she notes. “Even if you’re having a salad, you can add in avocado and some dried fruit and layer in those extra calories in a more nutrient-rich, healthy way.”

Protein shakes

Various supplemental shakes are also suggested by both Dr. Rome for children and Peart for adults. For kids, Dr. Rome recommends steering clear of powders in favor of the pre-mixed shakes you can buy off the shelves. “They pack a lot of calories into a container the size of a juice box and it’s perfect for a parent to prep the night before and give to a child in the morning for breakfast.”

Peart suggests protein shakes or even smoothies for some people who have smaller appetites. “For some, drinking may be more palatable (or easier to consume) than solid food, so that’s one way to get those calories,” she says. “And you can add ingredients like honey, fruit and even dry oats.”

Eating regularly throughout the day

Peart says one issue for some adults who want to add weight is that they have trouble eating large portions at every meal. “I’d recommend eating smaller, frequent meals and snacks throughout the day, about every two to three hours,” she says. “If you have a smaller appetite or something else that prevents you from eating as much from a traditional three-meal structure, this can help.”

Whether it’s adding in snacks to supplement meals or just eating more, smaller meals throughout the day, this can help you consume enough to gain the weight you need without forcing yourself to eat when you’re not hungry.

Avoid drinks right before dinner

Avoiding drinking large amounts of liquids before a meal can help keep your stomach a bit emptier if feeling full is an issue. “When you have something to drink before a meal, no matter what it is, it’s filling your stomach up so you may feel less hungry when you start eating,” Peart explains. Instead, drink between meals, not right before.

How quickly should weight be put on and still be safe?

Everyone is different, and our bodies react to food in different ways. So, it’s always essential that any plan to gain weight should be done under the supervision of a doctor or with the guidance of a registered dietitian. Anything to do with weight is a process that has to be done right, healthfully and safely.

For kids

“With most outpatient kids, you’re hoping for between a half-pound to two pounds a week,” says Dr. Rome. But, she adds, it could differ depending on your child and their conditions. “Partner with your pediatrician, a dietitian versed in weight gain — not just weight loss — and with an adolescent medicine doctor,” she suggests. “They can help make this journey more manageable.

For adults

Peart says by adding about 500 extra calories a day to your diet, most adults could see a gain of about a pound a week. The catch, though, is that some adults will add weight more easily than others for a variety of reasons. “A dietitian can individualize a plan for you,” she emphasizes. “They can work with you and your likes, dislikes and appetite size, and come up with a way for you to add weight in a healthy way.”