Non-alcoholic fatty liver disease (NAFLD): dietary triggers and treatment approaches

Researcher profiles:

• Dr Kirsten Coppell
• Associate Professor Michael Schultz
• Associate Professor Sally McCormick
• Miss Kiri Sharp

Non-alcoholic fatty liver disease (NAFLD) is now the most common liver disease in western countries affecting up to 30% of adults, and is estimated to increase to as high as 50% by 2030. NAFLD encompasses a spectrum of conditions associated with lipid deposition in hepatocytes, ranging from steatosis (simple fatty liver) to non-alcoholic steatohepatitis or NASH (fatty changes with inflammation and hepatocellular injury or fibrosis). Excess body weight is a key risk factor.

Most people with NAFLD are asymptomatic and the disease is often discovered through incidentally elevated liver enzyme levels. In the absence of any specific signs or symptoms, the diagnosis is typically made after excluding other causes of fatty liver and other causes of elevated liver enzymes.

Treatment options are limited, with pharmacotherapy for NAFLD still unclear. Weight loss through lifestyle modification is the only treatment option at present, as well as the treatment of associated conditions, including hypertension, dyslipidaemias and type 2 diabetes.

Prevalence of elevated liver enzymes in New Zealand

The prevalence of obesity dramatically increased in New Zealand between 1997 and 2008/09, from 17.0% to 27.7% in males and from 20.6% to 27.8% in females. Remaining blood samples from the 2008/2009 New Zealand Adult Nutrition Survey provided an opportunity to measure and describe the epidemiology of elevated liver enzymes in adult New Zealanders. This analysis has been completed and published:

• Coppell KJ, Miller JC, Gray AR, Schultz M, Mann JI, Parnell WR. Obesity and the extent of liver damage among adult New Zealanders: findings from a national survey. Obesity Science and Practice. 2015 Dec;1(2):67-77. doi:10.1002/osp4.13

Identifying dietary patterns that may trigger NAFLD

The Trigger study is comparing the effect of hypercaloric (excess energy intake) with isocaloric diets (usual energy intake) on the amount of liver fat in women with a healthy weight.  In addition, both of the diets will incorporate a period of calorie intake from moderately high proportions of fat, and then a period of calorie intake from moderately high levels of refined carbohydrates.

The amount of liver fat is being measured by proton magnetic resonance spectroscopy (H-MRS), along with additional markers of NAFLD such as liver function tests.

• Sharp KPH, Schultz M, Coppell KJ. Is non‐alcoholic fatty liver disease a reflection of what we eat or simply how much we eat? JGH Open: An open access journal of gastroenterology and hepatology. 2018 Mar 2;1-16. doi:10.1002/jgh3.12040

The dietary pattern of people with NAFLD

There are limited data describing the dietary habits of patients with NAFLD, with the few published studies mostly using patient recall for the nutritional assessments. Weighed dietary records (where all food and beverages are weighed at the time of consumption), while more intensive for the participant, provide a more accurate assessment.

We are undertaking a study to characterise the dietary pattern of patients with NAFLD and plan to undertake a long term dietary intervention study.

The feasibility of different dietary approaches for the treatment of NAFLD

Although it is established that gradual weight loss in those with excess weight affects the liver favourably in NAFLD, the most effective dietary approach is yet to be established. In general, patients are simply advised to lose weight, which may or may not be effective.

We are trialling the feasibility  and acceptability of two different dietary approaches for the treatment of NAFLD:

• a short term low calorie partial meal replacement (Optifast) diet followed by 'weigh-ins' with a nurse
• an intensive dietitian delivered evidence-based nutritional approach for the treatment and prevention of diabetes over a 6 month period

Presentations

Coppell KJ, Miller J, Schultz M, Gray A, Mann JI, Parnell W. (2013) The prevalence of abnormal liver enzymes in New Zealand: findings from the 2008/09 Adult Nutrition Survey. Proceedings NZ Society of Gastroenterology and NZNO Gastro Nurses Section Annual Scientific Meeting, Wellington 20-22 November. New Zealand Medical Journal 126:1387.