Q: I’m underweight for my height. Do I need to gain weight, and are there safe ways to do it?
First off, those height and weight charts you see at your doctor’s office are based on averages from large populations, and they shouldn’t be used to make decisions about a person’s individual ideal weight. Also, body mass index (the commonly used weight-to-height ratio to determine if you fall into the underweight, normal-weight, overweight, or obese category) is not a perfect measure of whether your weight is healthy, because it fails to give you a detailed look at how muscle tissue and fat each contribute to your overall body weight. Being underweight can be genetic, too. So if you are generally healthy and you feel strong and energetic day to day, you may not need to gain.
The best thing you can do if you think you’re underweight is see your doctor or a registered dietitian for a more thorough health evaluation. Then you can decide together whether you need to meet a goal weight and the best way to do it. The safest way to add pounds is to gradually up your calorie intake with nutritious, calorie-dense foods, like protein (chicken, fish, eggs), healthy fats (nuts, avocado, olive oil), starchy vegetables, and whole grains. It might also be helpful to switch up the number of times you eat during the day. You may feel full faster if you’re underweight, so if you’re eating more calorie-dense fats and proteins, it could be beneficial to have five or six smaller meals throughout the day as opposed to two or three bigger ones. Your MD may also suggest adding strength training exercises to your workout regimen to build muscle.
FYI: It’s possible to be underweight (or to suddenly lose weight) because of an illness or underlying health condition, like an overactive thyroid or celiac disease, which is also why it’s crucial to get guidance from a medical professional.
Health’s medical editor, Roshini Rajapaksa, MD, is assistant professor of medicine at the NYU School of Medicine.