Did you know that about two percent of American adults 20 and older are actually underweight? But being underweight isn’t any better for your health than being overweight. And believe it or not, gaining weight — the right way, at least — can be just as challenging as losing weight.
Sure, you can start gobbling down bags of chips and boxes of donuts, but just like when you’re losing weight, the quality of the calories you’re consuming are just as important as the quantity. If you’re trying to gain weight, odds are you’re aiming to gain muscle mass, not fat.
But a lot of things can influence the number on the scale, like height, gender, age, and genetics. On top of that, the scale can’t tell the difference between muscle, fat, bones, organs, etc., so it can’t tell you how fit or healthy you are.
You’ve probably heard of body mass index (BMI), which is a simple height-to-weight ratio: your weight (in kilograms) divided by the square of your height (in meters). That number determines which general weight category you fall into, according the Centers for Disease Control and Prevention (CDC):
- Below 18.5 = Underweight
- 18.5 – 24.9 = Normal or Health Weight
- 25.0 – 29.9 = Overweight
- 30.0 and Above = Obese
Like your bathroom scale, your BMI doesn’t take into account those aforementioned things that can affect your weight or directly measure fat, so the CDC acknowledges that BMI is not the final word on your fat levels or health. But it can be used to determine your general weight category and the possible health risks associated with each.
Instead, it may be wiser to focus on your body fat percentage, which measures your body composition and how much of that is fat. When you’re trying to gain weight, it’s a good ratio to be aware of to make sure you’re gaining muscle, not fat. It can help you set realistic nutrition and fitness goals and expectations.
A certain amount of fat is essential for a healthy body. If you’re underweight, you may be missing essential nutrients, which can affect key body processes; in addition, low body weight in women could lead to the loss of a menstrual cycle. Meanwhile, there are people who are at a healthy weight, but don’t have enough muscle on their frames.
In people who perform limited strength training, as well as those coming off of injuries or illnesses, muscle mass can frequently be lower than is optimal for good health. And your risk of having too-low levels of muscle increases over the years.
After age 30, muscle mass can decline by three to eight percent per decade, contributing to metabolic issues, loss of strength and mobility, and the likelihood of falls as you age. Improving muscle mass can lead to gains in strength, endurance, and functional living.
How much weight you can gain in a given amount of time depends on multiple factors, including your genetics, gender, age, and other factors. But generally, if you’re trying to sustainably gain lean mass, most people can build between 0.25 and 0.5 pounds per week.
Even if you’re trying to bulk up, it’s still important for your overall health that you’re filling your body with whole foods, says Davis. She notes that trying to gain weight by eating processed foods like soda, refined grains, bacon, and trans fats can increase your risk of conditions such as type 2 diabetes and cardiovascular disease. Instead, focus on healthy, balanced meals in proper proportions.