Body mass index, or BMI, is one way to tell if you're at a healthy weight for your height. While most people are concerned about a BMI that's too high and how it might affect health, if your BMI is too low, you may also be at risk for health issues. Increasing your BMI so you fall within normal parameters not only helps you look better, but feel better too. If you've tried making changes to your diet but are still having trouble gaining weight, talk to your doctor about the best way to increase your BMI.
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Estimating Your BMI
Start your fitness journey by measuring your starting BMI, so you can figure out roughly how much weight you need to gain. Calculate BMI using an online calculator, or follow this equation: BMI = weight in pounds / (height in inches x height in inches) x 703.
If you're underweight, with a BMI of 18.5 or lower, you may be more susceptible to illness and take longer to recover. A low BMI may also increase risk of respiratory and digestive problems, cancer and osteoporosis. Aim for a healthy BMI, which is between 18.5 and 24.9.
If you're 5 feet, 6 inches tall and weigh 110 pounds, for example, calculate your BMI like this: (110 pounds / 66 inches x 66 inches) x 703 = 17.8. To get to a healthy BMI of 19.0, you'd need to gain about 8 pounds.
Add Calories to Increase BMI
Eating more calories than your body needs increases your weight, which, in turn, increases your BMI. While the equation for weight loss is fairly straightforward, factors outside your control -- like your genetics -- make it a little more difficult to estimate your needs for weight gain.
Knowing the number of calories you need to maintain your current weight is a good place to start, especially if you're losing weight. For women, estimates range from 1,600 to 2,400 calories a day and for men, between 2,000 and 3,000 calories a day. To gain 1/2 to 1 pound a week, add 250 to 500 calories to your estimated needs. So for weight gain, women generally need from 1,850 to 2,900 calories a day, and men require 2,250 to 3,500 calories.
Some people may need to add more calories to gain weight. Closely track your intake and weight to adjust your calories up or down as needed to increase your BMI.
Increase Your BMI With Healthy Foods
While you technically can get your extra calories from any food, your best bet is to stick with a variety of nutrient-rich whole foods while you work on raising your BMI. Foods that rich in nutrients and high in calories include brown rice, granola, raisin bran cereals, bananas, dried apricots, avocados, sweet potatoes, peas, yogurt, milk, and fatty fish such as salmon and tuna, tofu, beans, lean red meat, nuts and seeds.
Give the foods you eat a little calorie boost using high-calorie add-ins such as nonfat dried milk, oil or cheese. Add dry milk powder to soup and hot cereal. Cook meats, grains and vegetables in oil and add cheese to sandwiches, salads or potatoes.
Add Muscle Weight
While some of the weight you'll gain when you're boosting your BMI will come from fat, make sure some of the gain comes from muscle to increase your sense of well-being. Carrying too much body fat actually puts you at the same risk for obesity-related illness as being overweight, even if you're at a healthy BMI. Regular strength-training is necessary to promote muscle gains. A good muscle-building program includes one exercise for each major muscle group, abs, chest, legs, shoulders, arms and back, performed two to three times, with each set containing four to eight repetitions. Consult your doctor before starting an exercise program to ensure safety.