Low-Carb Diet Aids Weight Loss in Liver Transplant Recipients With Obesity

Carolyn Crist

November 07, 2022

A low-carbohydrate diet appears to be an effective weight-loss intervention in liver transplant recipients with obesity as compared with a calorie-restrictive diet, according to interim findings presented at the annual meeting of the American Association for the Study of Liver Diseases.

In particular, the intervention showed significant improvements in the metabophenotype profile, including visceral adipose tissue and abdominal subcutaneous adipose tissue, said Mohammad Siddiqui, MD, a gastroenterologist and liver transplant specialist at Virginia Commonwealth University, Richmond.

"Weight gain and obesity after liver transplantation is common," he said. "Posttransplant obesity is associated with increased cardiometabolic risk burden, increased risk of cardiovascular disease and mortality, and overall mortality."

Previously, Siddiqui and colleagues have shown that posttransplant weight loss is difficult because of metabolic inflexibility and mitochondrial inefficiency. By specifically targeting carbohydrate utilization, metabolic flexibility could be restored in liver transplant recipients, he noted.

Siddiqui and colleagues conducted a randomized controlled trial of 27 adult liver transplant recipients with obesity for 24 weeks. The primary endpoint was change in weight, and the secondary endpoints involved metabophenotype, metabolic flexibility, mitochondrial function, and metabolic risk. The research team excluded patients with end-stage disease, terminal disease, use of weight-loss medications, pregnancy, or uncontrolled psychiatric illness that could interfere with adherence.

Among the participants, 13 were randomized to a calorie restrictive diet of less than 1,200-1,500 calories per day, and 14 were randomized to a low-carbohydrate diet of 20 grams or less per day. At enrollment, the participants underwent dietary, activity, skeletal muscle, and body composition assessments, as well as metabophenotype measurements of visceral adipose tissue, abdominal subcutaneous adipose tissue, muscle fat infiltration, fat-free muscle volume, and proton density fat fraction.

All participants were advised to maintain the same level of physical activity, which was measured through 7-day accelerometry. In addition, the patients were contacted every 2 weeks throughout the 24-week study period.

"We wanted to reinforce the dietary advice. We wanted to identify factors that may lead to compliance," Siddiqui said. "Multiple studies have documented that the more contact that patients have during weight-loss studies with medical personnel, the more effective those strategies are."

Overall, the dietary interventions were well tolerated, and neither group showed a significant change in renal function.

The average weight loss was –7.6 kg over 6 months in the low-carbohydrate group, as compared with –0.6 kg in the calorie-restrictive group.

The low carbohydrate diet also positively affected participants' metabophenotype profile, particularly fat deposits. As compared with the calorie-restrictive group, the low-carbohydrate group showed statistically significant improvements in visceral adipose tissue, abdominal subcutaneous adipose tissue, and muscle fat infiltration.

The liver proton density fat fraction, which is associated with fatty liver disease, decreased by 0.53% in the low-carbohydrate group and increased by 0.46% in the calorie-restrictive group, but the difference didn't reach statistical significance.

The fat-free muscle volume decreased by about 5% in the low-carbohydrate group. Siddiqui noted that the researchers don't know yet whether this translates to a decrease in muscle function.

In terms of metabolic risk, the low-carbohydrate diet did not affect serum lipids (such as triglycerides or cholesterol measures), renal function (such as serum creatinine, glomerular filtration rate, or blood urea nitrogen), or insulin resistance (through glucose or hemoglobin A1c). At the same time, among patients taking insulin at the time of enrollment, about 90% of patients randomized to the low-carbohydrate group were able to reduce insulin to zero during the study.

Upon completion of the current study, Siddiqui and colleagues hope to provide foundational safety and efficacy data for carbohydrate restriction in liver transplant recipients. In the ongoing study, the researchers are further investigating the dietary intervention impacts on metabolic flexibility, skeletal muscle mitochondrial function, atherogenic lipoproteins, and vascular function.

"Are we actually, on a molecular level, fixing the fundamental problem that liver transplant recipients have to improve outcomes?" he said. "We're doing very detailed profiling of these patients, so we will have data that shows how this actually affects them."

Siddiqui was asked about the sustainability of the low-carbohydrate diet, particularly with a restrictive parameter of 20 grams per day. During the COVID-19 pandemic, Siddiqui noted, the study was slowed and the research team was able to collect follow-up data.

"Surprisingly, we have a high rate of compliance, even after 6 months of therapy, and I think this has to do with a patient population that's been through cirrhosis and has almost died," he said. "They're far more compliant, and we're seeing that. We're also changing the physiology and improving mitochondrial function, which improves the weight loss and weight maintenance, though I don't know how long that's going to last."

The study sponsorship was not disclosed. Siddiqui reported no relevant conflicts of interest.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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