Due to their hedonic properties, sugar‐sweetened beverages (SSBs) may play a role in the development of metabolic diseases by favoring excess energy intake ( 1 ). In addition, fructose contained in SSBs stimulates hepatic de novo lipogenesis (DNL) ( 2 , 3 ) and increases intrahepatocellular lipid concentration (IHCL) ( 4 ). This suggests that fructose‐containing caloric sweeteners may be tightly associated with the development of non‐alcoholic fatty liver disease (NAFLD). Our primary aim was, therefore, to evaluate whether an intervention in which SSBs were replaced with artificially sweetened beverages (ASBs) would reduce markers of NAFLD in high‐SSB consumers with overweight or obesity.

Non‐normally distributed data were log‐transformed before statistical analysis. The effect of intervention on all outcomes was assessed by two‐way ANOVA with interaction, with time and intervention as independent variables. IHCL and VAT values were expressed as absolute (mmol/l and cm 3 , respectively) and relative values (i.e., % of values measured at the end of the run‐in period). Both intention to treat and per protocol analyses were performed and led to similar results and conclusions. Per‐protocol analyses on subjects having completed all IHCL measurements are displayed.

Thereafter, subjects were randomly assigned to consume their habitual SSB intake (control arm: CTRL) or replace their habitual SSB intake with ASB (intervention arm: ASB) during 12 weeks (week 5‐16). Randomization was stratified by sex. Every week, participants received a new batch of ASB or SSB packages, and were asked to return the empty packages on their next visit. Their food and non‐caloric beverage intakes were otherwise left ad ‐ libitum . Every other week, they reported to the Clinical Research Center (CRC) in the fasting state to have their body weight, body composition, blood pressure, and metabolic markers monitored. Their food intake, physical activity, body composition, and daily urinary fructose and sucrose excretion were measured again at weeks 10 and 16, and their IHCL and VAT after at week 16.

After inclusion, subjects entered a 4‐week run‐in period, during which they continued their usual SSB consumption (week 1‐4). During the fourth week, they wore an actimeter (DIGI‐WALKER SW‐2000, Yamax, Japan), recorded their food intake over two working days, and collected their urine over a 24‐hour period for the measurement of urinary fructose and sucrose excretion ( 5 ). They had then, on three separate days (a) their food intake calculated by a nutritionist, (b) their IHCL and visceral adipose tissue volume (VAT) measured with MRS ( 6 ), and (c) their body composition (bio‐impedancemetry), blood pressure, and fasting metabolic markers (plasma glucose, insulin, total triglycerides, total cholesterol, HDL‐cholesterol, AST, ALT, and uric acid) measured. Their insulin sensitivity was estimated from the HOMA‐insulin resistance index (HOMA‐IR).

Male and female subjects with BMI greater than 25 kg/m 2 and a daily consumption of two or more 22‐oz SSBs (carbonated soft drinks and sugar‐sweetened tea) were eligible. The experimental protocol was approved by the Ethical Committee for Human Research of the Canton de Vaud and registered on clinicaltrials.gov (NCT 01394380).

Fifteen participants (8 in ASB, 7 in CTRL) had IHCL greater than 60 mmol/l (corresponding to ca 5% liver fat). They had significantly higher BMI, VAT, TG, uric acid, AST, ALT, and lower insulin sensitivity and HDL‐cholesterol than the 12 participants with IHCL less than 60 mmol/l (Table 3 ). In this subgroup, ALT concentrations were significantly decreased with ASB.

During intervention, compliance estimated from returned packages was more than 90% in both ASB and CTRL. The evolution of IHCL, body weight, body composition and fasting metabolic markers is shown in Table 1 . IHCL, expressed in absolute values, were significantly reduced in both ASB and CTRL groups ( P < 0.05), and there was a significant interaction between group and time. When expressed in relative values, IHCL were reduced in the ASB group only, and group × time interaction showed a trend ( P = 0.06). Body weight, VAT, SAT, blood pressure, and blood metabolic markers were not significantly altered by intervention. Total energy, carbohydrate, and sugar intakes were significantly decreased in ASB, and unchanged in CTRL (Table 2 ). About 24‐hour urinary fructose excretion was significantly decreased with ASB, but remained unchanged in the CTRL group; 24‐hour urinary sucrose excretion did not change significantly in both groups (Table 2 ).

Of 128 potential participants screened by phone, 75 were scheduled for an inclusion visit, 35 were eligible, 2 declined enrollment, and 2 did not show up at the initial evaluation. About 31 participants were randomized, 18 to ASB, and 13 to CTRL. Four participants randomized to ASB dropped‐out during the study and 27 completed the study (14 in ASB and 13 in CTRL). Thirteen participants had BMI 25‐29.9 (ASB: 3 M, 3 F, CTRL: 3M, 4F), six had BMI 30‐34.9 (ASB: 2M, 1F, CTRL: 3M, 0F), and eight had BMI >35 (ASB: 3M, 2F, CTRL: 0M, 3F). Their IHCL concentrations were 25.6 ± 7.6, 134.7 ± 47.7, and 136.4 ± 31.8 mmol/l, respectively.

Discussion

In this study, we assessed whether replacing SSB with non‐caloric ASB would have potentially beneficial effects on liver lipid metabolism in high‐SSB consumers with overweight or obesity. Our results indicate that replacing SSBs by ASBs significantly decreased IHCL after 12 weeks. This effect was most important in subjects with high IHCL. There was no significant effect on insulin sensitivity and cardiovascular risk factors, or on VAT or total body fat, as expected in a 12‐week intervention trial.

Few other studies have specifically investigated how dietary sugar restriction effects markers of NAFLD. One randomized clinical trial assessed and compared the effects of controlled isocaloric diets containing glucose‐ or fructose‐sweetened beverages during 4 weeks in adolescents with overweight. IHCL and HOMA‐IR were not significantly different with fructose and glucose, but adipose tissue insulin sensitivity was lower with glucose (7). Another study reported that modest reductions in fructose and high glycemic index carbohydrate intake over a 6‐month period significantly decreased body fat, HOMA‐IR and ALT 12 adolescents with obesity and NAFLD (8). The present data provides further evidence that a reduction of SSB intake can improve NAFLD in adult subjects with overweight or obesity, and adds to the growing concern that excess sugar may adversely alter liver lipid metabolism (4). It further suggests that the effect of SSB reduction on IHCL is not directly associated with an increased whole‐body and hepatic insulin sensitivity.

Several prospective cohort studies show evidence that SSB consumption is associated with body weight gain as summarized in two recent meta‐analyses (9, 10). In contrast, many intervention studies have reported that addition of sugar calories did not significantly increase body weight in adults (11-13), and that substitution of SSBs with non‐caloric beverages in children failed to decrease body weight (14-16) or led to weight losses much less than expected from the reduction of SSB energy intake (17, 18). This may be due to the short duration of intervention. In the present study we therefore selected IHCL as a primary outcome to monitor metabolic changes induced by reduced sugar intake. This choice was guided by reports indicating that IHCL decreases within 48 hours of energy restriction in subjects with obesity (19) and increases significantly within 6‐7 days in normal‐weight healthy subjects overfed with fructose, glucose, or fat (6), and hence may be an early marker of energy balance.

The present study involved outpatients, and compliance to the intervention, assessed by monitoring the returned packages, was high in both arms. To further verify compliance, we monitored 24‐hour urinary fructose and sucrose excretion, which has been shown to provide a fair reflection of total sugar intake (20). We observed that 24‐hour fructose excretion significantly decreased with ASB, but not with CTRL. In contrast, there was no significant change in 24‐hour sucrose excretion. Although SSBs in Switzerland are sweetened with sucrose rather than high fructose corn syrup, they may nonetheless contain significant amounts of free fructose and glucose due to spontaneous inversion of sucrose during SSB storage. We therefore hypothesize that monitoring urinary free fructose may better reflect the consumption of SSBs due to their high content of free hexoses.

This study has several important limitations. First, it was performed on a small number of subjects, and may therefore lack statistical power. Second, participants included subjects with BMI between 25 and 30, and it is possible that the beneficial effects of the intervention may have been more important if we had focused on subjects with higher BMI. This hypothesis is supported by our observation that ASB led to important reductions in IHCL subjects with high IHCL and VAT, who also had high BMI. Third, we opted to replace SSB with ASB, instead of using water, and we cannot exclude that direct effects of artificial sweeteners (acesulfame K + either aspartame or sucralose) interfered with our results.