Although weight loss is an on-going concern for the average American -- the Centers for Disease Control and Prevention estimates that nearly 70 percent of adults in the United States are either overweight or obese -- gaining a few pounds is a very real goal for the small percentage of people who are underweight. Underweight adults, or those with a body mass index of less than 18.5, generally fall into two categories: relatively healthy individuals with a high metabolism or genetic tendency toward thinness, or those who struggle with low weight and poor health because of malnutrition, anxiety, stress, illness or an eating disorder.
If your low body weight stems from or is accompanied by other health concerns, talk to your physician before embarking on a weight-gain diet.
Calorie Balance Basics
For some, gaining weight can be just as difficult as losing weight is for others, but in both cases, the same basic principles apply. Taking in as many calories as your body uses each day -- through both metabolic functions and physical activity -- promotes a stable body weight that fluctuates little over time. Depending on your age, activity level, metabolism and other individual factors, estimated calorie needs range from 2,000 to 3,000 calories a day for men, and 1,600 to 2,400 calories a day for women. Consuming fewer calories than you need each day, or going into caloric deficit, promotes weight loss as your body uses fat stores to meet its energy needs. Boosting your daily calorie intake, or going into caloric excess, on the other hand, leads to weight gain.
A Healthy Gain Rate
No hard and fast rules exist as to the number of extra calories you should consume on a weight-gain diet, partly because some people gain weight more readily than others. Aiming for a slow, steady weight gain -- or about a pound a week -- gives your body time to adjust to the increase. To gain a pound in one week, the average person needs to consume an extra 3,500 calories a week, or 500 calories per day. But if you're trying to regain weight after a stressful period or an illness, you may readily gain a pound each week with this increase; however, if you're naturally thin or have a high metabolism, you may gain less or even very little. If you're naturally underweight, shifting a bit further into calorie excess, steadily and deliberately, can help you find the right amount of calories for weight gain.
Diet and Eating Strategies
Actively trying to gain weight is not a license to eat whatever you want: A high-quality diet is just as important during weight gain as it is during weight maintenance and weight loss. Although junk food can be high in calories, it's typically low in nutrients, bad for your health, and comprises two leading sources of empty calories, refined grains and added sugars, both of which contribute to chronic disease, according to the Harvard T.H. Chan School of Public Health.
Instead, add healthy calories to your diet by boosting your intake of nutrient-dense, energy-dense foods like avocado, nuts, seeds, olive oil, cheese and whole-milk yogurt. Eat plenty of fruits and vegetables, and include hearty whole grains, dried beans, peas and lentils, lean proteins and fatty fish such as tuna or salmon in your diet. The Academy of Nutrition and Dietetics recommends using nutritious, calorie-dense foods as toppings on your usual fare; add some pumpkin seeds and a few dried apricots to your oatmeal, grate some cheese over a bowl of stew or add some chopped avocado to a fresh salad.
How you eat your calories can be as important as quality and quantity, particularly if you're dealing with a curbed appetite. While a typical weight-gain diet consists of three large meals a day in addition to two or more snacks, someone with a small appetite might find that eating five or six mini-meals throughout the day is more doable.
Gain Muscle, Not Fat
A healthy diet and a steady weight-gain rate help put your body in position to convert excess calories into lean mass, but strength training is what makes it happen. Unlike aerobic exercise, which burns excess calories, strength training helps convert excess calories into muscle and bone tissue. Whether it's in the form of body-resistance exercises like squats, lunges, yoga poses or Pilates mat exercises, or is accomplished with dumbbells or on resistance machines, making strength training your main form of exercise helps ensure that the extra calories you're eating aren't stored as fat.
- Centers for Disease Control and Prevention: Obesity and Overweight Statistics
- Centers for Disease Control and Prevention: Prevalence of Underweight Among Adults Aged 20 Years and Over -- United States, 1960–1962 Through 2007-2010
- Center for Nutrition Policy and Promotion: Estimated Calorie Needs per Day by Age, Gender, and Physical Activity Level
- Centers for Disease Control and Prevention: Finding a Balance
- American Council on Exercise: Putting on the Pounds
- Academy of Nutrition and Dietetics: Healthy Weight Gain
- NHS Choices: Underweight Adults
- Harvard T.H. Chan School of Public Health: Food and Diet