Poor Diet Quality Linked to Body Fat Distribution in Adults with Cystic Fibrosis, Study Shows

Adults with cystic fibrosis, compared with healthy individuals, have poorer diet quality and increased accumulation of visceral adipose tissue, which is associated with higher sugar intake and fasting glucose levels, a study reports.

The study, “Visceral adipose tissue is associated with poor diet quality and higher fasting glucose in adults with cystic fibrosis,” was published in the Journal of Cystic Fibrosis.

Poor nutrition is known to promote progression of cystic fibrosis (CF), and clinicians have no clear restrictions on high-caloric diets for these patients. In fact, clinicians encourage CF patients to follow a high-calorie, high-fat diet to meet their recommended healthy body mass index (BMI). However, the long-term impact of an unrestricted diet in adults with CF is unknown.

As glucose intolerance and CF-related diabetes are reportedly increasing among CF adults, a better understanding of the role of diet on clinical outcomes is needed.

Therefore, researchers at the Emory University School of Medicine in Atlanta analyzed the diet quality and body fat distribution in CF patients, compared with healthy individuals. They also looked at how both parameters correlated with patients’ clinical outcomes, namely fasting blood glucose levels and lung function.

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Measuring fasting glucose levels ­­­­— which indicate the amount of glucose (sugar) in the blood after overnight fasting ­­­­— is a way to diagnose those at risk for diabetes.

The study enrolled 49 participants, including 24 adults with CF (from 18 to 50 years old), and 25 age-matched healthy subjects. All CF patients had pancreatic insufficiency, characterized by deficient production of pancreas-specific digestive enzymes.

The quality of the participants’ diet, which was recorded before the beginning of the study, was assessed using the Healthy Eating Index 2015 (HEI-2015). The HEI-2015 scores range from 0 to 100, with a score of 100 indicating the highest diet quality.

Total body composition and distribution were assessed by dual energy X-ray absorptiometry, a technique that relies on an improved form of X-ray technology commonly used to measure bone density.

Researchers found that adults with CF had significantly lower HUI-2015 scores compared with healthy controls, which reflected an overall worse diet with higher intake of added sugar, trans-fatty acids, and refined grains, and lower consumption of total fiber and whole grains.

CF patients had a higher median total energy intake (2,673 kcal/day) compared with healthy subjects (1,914 kcal/day). They consumed on average 136% of the estimated Dietary Reference Intake for daily calorie requirements.

When analyzing blood glucose, 46% of the patients had CF-related diabetes, and 25% had impaired glucose tolerance, with 29% of the patients showing normal glucose tolerance. CF participants had increased levels of fasting glucose compared with healthy subjects, reflecting an hepatic deregulation in glucose production, or insulin resistance.

The standard measure to determine satisfactory nutritional status in CF patients is achieving or maintaining a sex-specific BMI. However, according to the team, relying exclusively on BMI presents several limitations, as it does not discriminate between lean and fat body mass, or the distribution of body fat.

Researchers found that, compared with healthy subjects, CF patients had increased visceral adipose tissue (VAT) accumulation, which was higher in males compared with females. VAT is correlated with metabolic syndrome and cardiovascular disease in the general population. Interestingly, researchers saw that increased VAT in CF patients was associated with added sugar intake and higher fasting glucose.

However, no differences were seen in BMI, total fat mass, and lean body mass between CF adults and healthy individuals.

Lung function, assessed only in CF patients, showed a positive association with lean body mass.

The results suggest that, compared with healthy individuals, adults with CF have poor quality diets and increased amount of VAT, which are linked with higher levels of fasting glucose.

“This study highlights the importance of increasing diet quality and assessing body composition and fat distribution in the CF population,” the researchers wrote.

“Larger, prospective studies are needed to determine if body fat distribution and dietary intake are causally related to clinical outcomes, and if they better identify at-risk individuals with CF and provide targets for future interventions,” the team added.