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Consuming saturated fatty acids promotes liver fat accumulation
Adults with overweight or obesity assigned to an 8-week diet that included muffins made with palm oil experienced an increase in liver fat and circulating ceramides that was not observed in similar adults who ate muffins with sunflower oil during the same period, according to findings published in The Journal of Clinical Endocrinology & Metabolism.
“It clearly matters which type of fat you eat for the development of fatty liver,” Ulf Riserus, PhD, MMed, associate professor in clinical nutrition and metabolism at Uppsala University, Sweden, told Endocrine Today. “Eating excess calories from plant-based polyunsaturated oils does not seem to cause any accumulation of fat in the liver, in clear contrast to saturated fats that markedly increases liver fat accumulation despite a similar excess calorie intake. These findings could have great implications for the prevention of fatty liver and [nonalcoholic fatty liver disease], as choosing the right type of fat in the overall diet can counteract these disorders.”
Riserus and colleagues analyzed data from 60 adults with overweight or obesity (BMI between 25-32 kg/m²) recruited by local advertising for the LIPOGAIN-2 study, a 12-week, randomized, double-blind, parallel-group trial conducted from August 2014 to June 2015. Researchers randomly assigned participants to eat muffins containing refined sunflower oil (high in omega-6 polyunsaturated fatty acids [PUFA], mainly linoleate; n = 30; mean age, 42 years; 12 women) or refined palm oil (high in saturated fatty acids, mainly palmitate; n = 30; mean age, 42 years; 11 women) for 8 weeks, as part of a habitual diet to be consumed anytime during the day. Diets were adjusted weekly (altered by 1 muffin per day depending on rate of weight gain) to achieve a 3% weight gain (average, 2.9 muffins added). At the end of the overfeeding period, researchers switched participants to a 4-week, low-calorie diet consisting of 800 kcal per day.
Liver and pancreas fat content and volume of total body and visceral fat were assessed via MRI; researchers also assessed ceramides from serum and adipose tissue. Dietary intake was assessed with 4-day, weighed food records at baseline and week 8. Participants also completed an oral glucose tolerance test.
Body weight gain was similar in the sunflower oil and palm oil muffin groups (mean, 2.31 kg vs. 2.01 kg; P = .05). However, researchers observed a 53% relative increase in liver fat content among participants assigned to the palm oil muffin group vs. a mean 2% decrease in liver fat in the sunflower oil muffin group (P = .001 for between-group difference).
“Despite similar weight gain, PUFA did not increase liver fat or liver enzymes or cause any adverse effects on blood lipids,” the researchers wrote.
Consuming palm oil muffins had no differential effect on the accumulation of visceral fat, pancreas fat or total body fat vs. sunflower oil muffins, according to researchers. The consumption of palm oil muffins was consistently associated with increases in circulating ceramides, changes the researchers noted were moderately associated with liver fat changes and proposed markers of hepatic lipogenesis.
The adverse metabolic effects of saturated fatty acids were reversed by calorie restriction, Riserus said.
“Since enhanced liver fat accumulation is the starting point for a number of severe liver diseases and also may contribute to developing dyslipidemia and type 2 diabetes, a diet that stops this process can be a potentially important clinical tool for both preventing and treating fatty liver and its related metabolic disorders.” Riserus said. “We are now conducting a more long-term study with different types of diets, including the promising benefits of polyunsaturated fatty acids in individuals with fatty liver and type 2 diabetes.” – by Regina Schaffer
For more information:
Ulf Riserus , PhD, MMed , can be reached at Uppsala Science Park, Department of Public Health and Caring Sciences, Clinical Nutrition and Metabolism, 75185 Uppsala, Sweden; email: ulf.riserus@pubcare.uu.se.
Disclosures: The Swedish Research Council sponsored this study. The authors report no relevant financial disclosures.