A randomized controlled trial: the effect of inulin on weight management and ectopic fat in subjects with prediabetes

Abstract

BackgroundFat infiltration of the liver, muscle and pancreas is associated with insulin resistance and risk of diabetes. Weight loss reduces ectopic fat deposition and risk of diabetes, but is difficult to sustain to due to compensatory increases in appetite. Fermentable carbohydrates have been shown to decrease appetite and food intake, and promote weight loss in overweight subjects. In animal studies, fermentable carbohydrate reduces ectopic fat independent of weight loss. We aimed to investigate the effect of the fermentable carbohydrate inulin on weight maintenance, appetite and ectopic fat in subjects with prediabetes.MethodsForty-four subjects with prediabetes were randomized to 18 weeks’ inulin or cellulose supplementation. During weeks 1–9 (weight loss phase) all subjects had four visits with a dietitian to guide them towards a 5 % weight loss. During weeks 10–18 (weight maintenance phase) subjects continued taking their assigned supplementation and were asked to maintain the weight they had lost but were offered no further support. All subjects attended study sessions at baseline, 9 and 18 weeks for measurement of weight; assessment of adipose tissue and ectopic fat content by magnetic resonance imaging and magnetic resonance spectroscopy; glucose, insulin and GLP-1 levels following a meal tolerance test; and appetite by ad libitum meal test and visual analogue scales.ResultsBoth groups lost approximately 5 % of their body weight by week nine (−5.3 ± 0.1 % vs −4.3 ± 0.4 %, p = 0.13, but the inulin group lost significantly more weight between 9 and 18 weeks (−2.3 ± 0.5 % vs −0.6 ± 0.4 %, p = 0.012). Subjects taking inulin had lower hepatic (p = 0.02) and soleus muscle (p < 0.05) fat content at 18 weeks compared to control even after controlling for weight loss and consumed less at the ad libitum meal test (p = 0.027). Fasting glucose significantly decreased at week nine only (p = 0.005), insulin concentrations did not change, and there was a significant increase in GLP-1 in the cellulose group at 9 and 18 weeks (p < 0.03, p < 0.00001).ConclusionInulin may have a two-pronged effect on the risk of diabetes by 1) promoting weight loss 2) reducing intrahepatocellular and intramyocellular lipid in people with prediabetes independent of weight loss.Trial registrationClinical trial number: NCT01841073.Electronic supplementary materialThe online version of this article (doi:10.1186/s12986-015-0033-2) contains supplementary material, which is available to authorized users.

The effects of dietary supplementation with inulin and inulin‐propionate ester on hepatic steatosis in adults with non‐alcoholic fatty liver disease

“…9 It could be suggested that the elevated ratio of colonic propionate : acetate promoted by IPE supplementation may have prevented the accumulation of liver fat observed in the inulin-control group by impairing hepatic acetate metabolism. This proposed mechanism is concordant with the results from Wolever and colleagues, who showed using stable isotope technology that propionate inhibits incorporation of colonic [1,[2][3][4][5][6][7][8][9][10][11][12][13] C] acetate into plasma lipids in humans. 7 Studies using rat hepatocytes have also highlighted that propionate inhibits lipid synthesis when acetate is a major source of acetyl-CoA.…”

“…Our previous work showed that 30 g/d ITF supplemented into the habitual diet of overweight adults with normal glycaemic control had no effect on IHCL . In contrast, a superior reduction in IHCL in adults with prediabetes was found when a weight‐loss diet was combined with 30 g/d ITF supplementation . The serendipitous observation in the current study is that supplementing 20 g/d inulin into a habitual weight‐maintaining diet raises IHCL and further exacerbates glucose homeostasis in adults with NAFLD.…”

“…20 This may explain the disparate effect of inulin supplementation on liver fat content in the current study compared with our previous investigation when inulin intervention was added to a hypocaloric diet that achieved a~5% reduction in body weight. 13 IPE supplementation did not significantly raise IHCL content, as observed within the inulin-control group. The contrasting outcome could be because of differences in the amounts of acetate derived from inulin fermentation throughout the supplementation period, as the inulin-control group were provided with a greater amount of inulin compared to IPE (20 g/d vs. 14.6 g/d).…”

“…Interestingly, diet‐induced body weight loss in mice has been shown to markedly reduce insulin levels and rates of hepatic DNL, whilst the expression of hepatic DNL‐related genes is also reduced by states of chronic negative energy balance . This may explain the disparate effect of inulin supplementation on liver fat content in the current study compared with our previous investigation when inulin intervention was added to a hypocaloric diet that achieved a ~5% reduction in body weight …”

“…12 In contrast, a superior reduction in IHCL in adults with prediabetes was found when a weight-loss diet was combined with 30 g/d ITF supplementation. 13 The serendipitous observation in the current study is that supplementing 20 g/d inulin into a habitual weightmaintaining diet raises IHCL and further exacerbates glucose homeostasis in adults with NAFLD. Taken together, our data suggest that ITF supplementation does not have a homogenous impact on hepatic lipid content in humans, and its effects may depend on the pre-existing metabolic health of the individual and the energy-balance promoted by the background diet.…”