Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) modulator drugs target the defective gene present in people with CF. This results in improved flow of sodium and chloride within the cells, and reduces build-up of mucus which damages the lungs, pancreas and other organs. Significant improvements in overall quality of life and lung function have been documented for people taking these drugs.
Nutrition and Modulators
Some people (not everyone) may gain weight when they commence a CFTR modulator without making any changes to their diet or exercise regime. Whilst the exact reason why is still being researched, it is predicted that this is due to improved overall health. As lung function improves, individuals may not need to eat as much to account for work of breathing.
As pancreatic function improves, individuals may start absorbing more fat and nutrients from food. These factors combined mean that you may not need to eat as much as previously to maintain your weight. The impact of a CFTR modulator on weight changes will depend on the type of modulator, CF genotype and individual circumstances, therefore it is important to meet with your CF dietitian regularly for personalised advice.
Weight Gain
For some people weight gain will be desirable, particularly if you were previously underweight or struggled to maintain your weight. It is encouraged to continue following a high energy, high fat, and unrestricted diet until you are comfortably maintaining a BMI within the optimal range.
For some people weight gain may be unwanted, particularly if you were previously a healthy weight or overweight. Dietary changes may be recommended if you are gaining weight rapidly or your weight shifts above the healthy weight range. In this case it is important to talk to your CF dietitian and doctors for tailored recommendations. Regardless of your weight, it is still important to eat regular meals and eat a variety of foods.
You can also use the following strategies as a starting point:
- Focus on making the foundation of what you are eating from the five food groups (fruit, vegetables, dairy products, lean meat and meat alternatives and wholegrain cereal products)
- Reduce the amount of processed foods you are eating such as cakes, biscuits, takeaway food and soft drink
- Include 5 serves (handfuls) of vegetables each day, which provide beneficial nutrients and will keep you full
- Replace fruit juice or dried fruit with whole fruit and limit to two pieces per day
- Reduce the amount of fat (oil, butter) used in cooking or added at the table
- Increase physical activity as able
If you become unwell and are unable to eat as much or as regularly as usual, you should halt attempts to lose weight and re-introduce higher energy and fat foods until you recover. It is important that you are not losing weight when you are unwell as this weight usually comes from muscle mass rather than fat mass.
Taking Your Modulators Correctly
In order for CFTR modulators to be absorbed in the body, they need to be taken with a substantial fat containing food. It can be hard for some people to take modulator medicine correctly in the morning if they usually only have a light breakfast, or skip breakfast.
The table below outlines the fat content of some typical breakfast foods. Your evening dose can be taken with your usual dinner meal. Talk to your CF pharmacist or medical team about your exact requirements.
