New insights into personalised nutrition for children with cystic fibrosis on CFTR modulators

A recent survey reveals that CFTR modulators are prompting a shift from standard high-calorie diets toward more personalised nutritional management in children with cystic fibrosis, as weight responses vary and disordered eating concerns emerge.

CFTR modulators are changing how clinicians think about nutrition in children with cystic fibrosis, with a new survey suggesting that weight management now needs to be more individualised than the traditional high-calorie approach. The study, published in Nutrition in Clinical Practice, found that parents and caregivers generally saw their children’s weight and eating patterns shift after treatment began, prompting researchers to call for nutrition plans that reflect growth, food preferences and response to therapy.

Researchers in the US surveyed 49 parents and caregivers of 60 children with cystic fibrosis, most of them around eight years old. Almost all of the children were taking pancreatic enzyme replacement therapy, and all were receiving a CFTR modulator, most commonly Trikafta, the triple combination of elexacaftor, tezacaftor and ivacaftor. Among the 46 children who had been on a modulator for more than a year, about two-thirds were reported to have gained an appropriate amount of weight, although a sizeable minority gained too little, gained none at all, or gained more than expected.

The findings fit with earlier research showing that weight changes after CFTR modulator treatment are not uniform. A study in Respiratory Research found that weight gain after starting elexacaftor, tezacaftor and ivacaftor varied considerably between patients, while research in Pediatric Pulmonology suggested that younger children and those with more pulmonary exacerbations in the previous year were more likely to see the largest weight gain over six months. Other work has pointed in a different direction altogether: a prospective study in Frontiers in Pediatrics reported no significant change in weight, height or body mass index after lumacaftor/ivacaftor, even though some nutritional markers improved.

In the new survey, about half of the children who had used a modulator for more than a year had some change to their diet, often because their weight had improved enough for families to cut back on calorie-dense foods, supplements or tube feeding. Nearly half had followed a high-fat diet in the previous six months, reflecting the long-standing emphasis on helping children with cystic fibrosis gain enough weight. But researchers said CFTR modulators may mean that some children no longer need the same level of calorie loading, while others still struggle to maintain a healthy weight and may still need support.

The study also raised concerns about eating behaviours. Parents and caregivers reported possible disordered eating patterns in about a third of the children, including restrictive food rules, over-exercising, meal skipping, rigid rituals around eating and frequent weighing. Most families were comfortable discussing weight with the care team, and 91% said they talked about it at every clinic visit, but some described the subject as emotionally difficult after years of intensive weight-focused care. One participant told the researchers, “We no longer have to monitor everything she eats. She no longer drinks weight gainer shakes and is at a healthy weight,” while another said, “It’s probably the biggest challenge we have faced in CF care, and I definitely have some trauma from it.”

Taken together, the results suggest that CF teams may need to move away from a one-size-fits-all nutrition message. That view is reinforced by broader research into CFTR modulators: a study published in Frontiers in Pharmacology found that weight gain with ivacaftor was mainly due to increases in fat mass, not lean tissue, and recommended early counselling on healthy eating and exercise. A separate case series in the Journal of Clinical Pharmacology described clinically significant oedema and fluid-related weight gain in some patients on CFTR modulators, underscoring that not every rise on the scale reflects the same biological change. For families and clinicians, the message is increasingly clear: weight monitoring remains essential, but the goal is now precision rather than simply more calories.