Nutritional Basics

Individuals with cystic fibrosis require more energy to breathe normally, fight lung infections and compensate for poor digestion. For these reasons, they need more calories than people without CF.

7 min read
In this article
  • Energy needs of people with CF are estimated to be 1 ½ to 2 times the needs of those without CF. 
  • Your dietitian can offer some simple ways to add calories to the food you already eat.
  • High-calorie supplements can be used to boost calories, but they shouldn't be used to replace meals. 

Energy needs of people with CF are estimated to be 1 ½ to 2 times the needs of those without CF. A high-calorie, high-fat diet, with 40 percent of total calories from fat is generally recommended.1

There is no one specific recommended method to determine energy needs. The goal is usually sustained weight gain and growth in children and teens, and weight gain or maintenance for adults.

Your Body Mass Index

Just how much should you weigh? That answer will vary, largely depending on your current weight, your height and the nutritional goals that you and your care team set for your health.

To track weight relative to height in individuals with CF, your care team uses different measurements:

  • Weight-for-length for children under age 2.
  • Body Mass Index (BMI) percentiles for those ages 2 to 20 (because height fluctuates so much).
  • A numerical BMI for people over age 20.

BMI is calculated by dividing your body weight in kilograms (kg) by your height in meters squared (m2). Calculate your BMI with this online BMI calculator from the Centers for Disease Control and Prevention (CDC). You can also ask your CF care team about your BMI during your next visit.

The CF Foundation recommends that women maintain a BMI of at least 22 and men, a BMI of at least 23. For people under age 21, BMI should be at or above the 50th percentile on the CDC growth chart.

The data show that for adults with CF, pulmonary function and nutrition status are related and improvements in one metric are associated with improvements in the other.

Fitting in the Calories: Your Diet

People with CF typically need up to twice the amount of daily calories as others who are of similar age and weight. To gain weight, you will need to take in about an extra 500 calories a day.

Spend some time thinking about what your weight gain goal should be. Discuss what you want to accomplish with the dietitian on your CF care team. Together you can figure out how to best reach your BMI goal.

Your dietitian can offer some simple ways to add calories to the food you already eat. We're not talking about anything out of the ordinary.

You can get those extra 500 calories from foods like these:

  • A grilled ham and cheese sandwich with avocado.
  • A bowl of spaghetti with sauce, extra cheese and olive oil.
  • A peanut butter and jelly sandwich and a glass of whole milk.
  • Two large handfuls of nuts or trail mix.
  • A medium-sized bean, cheese and salsa burrito.
  • A grilled chicken Caesar wrap.
  • A protein bar and a nutritional supplement beverage such as Ensure or Boost.
  • Two slices of cinnamon raisin toast with butter and one cup of instant breakfast drink.

Or you can add 100 calories to each meal and snack, so that it equals 500 calories. Here are some 100-calorie additions that you can make:

  • 4 tablespoons of avocado.
  • 2 slices of bacon.
  • 1/4 cup of shredded cheese.
  • 2 tablespoons of chopped nuts.
  • 1 tablespoon of peanut butter, other nut butter or sunflower seed butter.

As you can see, nothing on this list costs much or takes much effort to make. In other words, you can get your 500 extra calories eating on the go. Make sure that you schedule your snacks and have your enzymes with you, so you get the most out of every calorie you take in.

Remember, these extra calories should be part of a well-balanced diet. A 2012 study showed an overdependence on saturated fat intake in individuals with CF and a low polyunsaturated fat intake.2 As individuals with CF live longer, this imbalance increases the risk of heart disease. Make sure to incorporate unsaturated fats from foods such as avocados, nuts and oils. Walnut and flaxseed oils are good choices because they contain fats that reduce inflammation.

For a variety of reasons, many people have switched to a vegetarian diet. If you have CF, it is possible to create nutritious plant-based meals and snacks that pack the protein, fats and carbohydrates you need. Read Cystic Fibrosis and the Vegetarian Diet to learn tips and recipes.

Nutritional Supplement

High-calorie supplements can be used to boost calories, but they shouldn't be used to replace meals. Instead, nutritional supplements should be taken along with a meal or as a substitute for a lower-calorie snack.

Nutritional supplements come in a variety of forms. You can get flavored powders that you can mix with milk, ready-made milk-based shakes, and high-calorie and high-protein juices. You also can get individual fat, carbohydrate or protein powders that you can mix into drinks. Talk to your CF dietitian about the right choice for you.

How Much Water Do I Need?

Every cell in the body needs water to work properly. You can get most of the water you need from what you drink, but you also can get water from many foods.

The amount of fluid you need depends on your age, weight, activity level, general health and the climate. Do not wait until you feel thirsty to drink water. By the time your brain signals you to drink, you may already be dehydrated.

Some symptoms of dehydration are headache, nausea, loss of appetite and fatigue. You also can tell if you are dehydrated by looking at the color of your urine. Urine should be clear or a pale yellow. If your urine is dark yellow or brownish, you are not getting enough fluids. Vitamins and medications may temporarily affect color. Your CF dietitian can help you figure out how much fluid you need each day and help you decide on the best sources.

All the beverages in the table below are good sources of water.

Beverages Nutrients Calories
Water None None
Whole milk and milk beverages High High
Fruit juices Medium to high Medium
Sports drinks None Low to high
Soda, coffee, tea None None to high

In addition to beverages, many foods have lots of water.

Food Percent Water
Soup 92
Watermelon 92
Yogurt 91
Orange 87
Cooked cereal 85
Jarred baby food 85
Potato 77
Pudding 75
Egg 75
Cooked pasta 66
Ice cream 61


1 Quick, Virginia, Byrd-Bredbenner, Carol. Disordered Eating and Body Image in Cystic Fibrosis. In: Diet and Exercise in Cystic Fibrosis. San Diego, CA: Academic Press; 2015:11-12.
2 Smith, C, Winn, A., Seddon, P., Ranganathan. A fat lot of good: Balance and trends in fat intake in children with cystic fibrosis. J Cystic Fibr. 2012 March;11(2):154-157.

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