Liver Fat Accumulation in Response to Overfeeding With a High-fat Diet

A Comparison Between South Asian and Caucasian Men

Siti N. Wulan; Vera B. Schrauwen-Hinderling; Klaas R. Westerterp; Guy Plasqui

Disclosures

Nutr Metab. 2015;12(18) 

In This Article

Discussion

We found that South Asian and Caucasian men with the same body fat percentage (not the same BMI) showed no difference in the baseline liver fat content. Furthermore, visceral fat area was found to be the significant predictor of liver fat content at baseline. Liver fat content increased similarly in both groups in response to short term overfeeding with a high fat diet.

Earlier cross-sectional studies reported higher liver fat content in South Asians when compared to BMI-matched Caucasians,[15] suggesting a higher susceptibility to ectopic fat storage in Asians. It is known that, due to differences in body composition, matching for BMI will result in a higher body fat percentage in the Asian group, which may be a confounding factor. Therefore, in the current study, we chose to match subjects with respect to whole body fat percentage, as determined by a three-compartment model. When these groups, with similar body fat percentage, were compared, hepatic lipid content was similar, and in both groups, body fat percentage and the visceral adipose tissue area (which was also similar between groups) were predictive for baseline liver fat content. This is in line with earlier studies, where visceral fat has been reported to be associated with liver fat content in Caucasian populations[18,40,41] as well as a South Asian population.[15]

It was also reported that South Asians might be more susceptible to the negative metabolic effects of high-fat high-caloric diets. Also here, the difference in body fat percentage between Asians and Caucasians (when matched for BMI) may have played a role. To investigate whether Asians still have higher susceptibility to a high energy, high-fat diet, when controlled for body fat percentage, we investigated hepatic fat storage after overfeeding with a high fat diet for 4 days in groups matched for body fat percentage. We expected to create a massive positive energy balance that favors fat accumulation rather than fat oxidation.

Earlier studies already showed that high fat diets can increase liver fat content in a relatively short period of time. A dietary intervention with an isocaloric high fat diet[21,23] resulted in an increase in liver fat content by 35 % after 2 weeks in obese Caucasian women[23] and by 17 % after 3 weeks in overweight Caucasian men.[21] In the latter study, fat accumulation was observed after one week with no further increase in the following weeks, suggesting an adaptation.[21] This is also in accordance with a study in healthy male Caucasians by van der Meer et al.[22] showing that a 2–3 fold increase in liver fat content had already occurred after 3 days consumption of supplemental cream (800 ml, 280 g fat) added to the regular diet.

Here, we conducted a short-term intervention with a high fat diet (4 days), by overfeeding subjects with 50 % energy above the individual requirements and 60 % of energy from fat. The mean increase in liver fat content was 33 and 34 % in South Asians and Caucasians respectively. Thus in South Asian and Caucasian men with the same body fat percentage, and similar liver fat content at baseline, the increase in liver fat in response to short-term overfeeding with a high fat diet was similar. The inter-individual variability in the baseline liver fat is rather high, especially in the Caucasian group and is partially explained by the range of body fat percentages included (range from 17 to 31 %, see also Fig. 1). The increase in liver fat content is modest, but very consistent and highly significant. The inter-individual variability in the percentage changes in liver fat content is higher than differences between ethnicities. Therefore, when carefully matched for body fat percentage (rather than BMI) we find no indication of Asian subjects being more susceptible to overfeeding.

In a study with very similar set-up, we found insulin levels to be increased in both, Asians and Caucasians,[42] which may be favoring hepatic fat storage and therefore underlie the present findings. During overfeeding, the postprandial state, including high insulin levels, is slightly extended as a result of extended meal consumption.[42] Insulin was also reported to suppress hepatic lipid oxidation[43] and to promote the synthesis and storage of triglycerides in the liver.[44]

Interestingly, even though absolute amount of visceral adipose tissue was similar between the two groups, it is striking that due to smaller body size in Asians, the visceral adipose tissue depot represents a higher percentage of total abdominal adipose tissue. It was hypothesized that the high prevalence of metabolic diseases in South Asians might be attributed to a smaller subcutaneous adipose tissue compartment and a relatively enlarged VAT. As obesity develops, South Asians could exceed the storage capacity of subcutaneous adipose tissue before Caucasians do and develop metabolic complications.[16] Our data confirm that in the abdominal region, South Asians have a relatively enlarged VAT and a relatively smaller subcutaneous adipose tissue compartment. Lear et al.[45] reported that throughout a range of total body fat mass, South Asians had less VAT with total body fat > 37.4 kg, but more VAT when total body fat was below 37.4 kg than did Europeans, after adjusted for age, sex and household income. In our study, South Asian men had a range of absolute fat mass between 7–29 kg and thus the relatively higher VAT was consistent with a previous study.[45] However, our data showed that despite a relatively higher percentage of VAT area in South Asians, liver fat content at baseline did not differ between ethnicities and also the response to overfeeding was very similar in the two groups.

The limitation of our study is that we induced exposure to excess FFA from the diet in a short-term period, thus it cannot elucidate the differences, which may be observed in a longer period. Additionally, the low number of subjects may not represent the general population in South Asian and Caucasian and only young men were investigated. Although we matched the subjects for body fat percentage, we found variation in the baseline liver fat content and the variation was larger in Caucasians which was not ideal. Taken into account the limitations, this was a well-controlled dietary intervention study using state of the art techniques to investigate liver fat content and body composition in response to overfeeding and no such studies have been performed comparing two ethnicities.

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