Saccharin and aspartame, compared with sucrose, induce greater weight gain in adult Wistar rats, at similar total caloric intake levels

The Effect of Nonnutritive Sweeteners Added to a Liquid Diet on Volume and Caloric Intake and Weight Gain in Rats

OBJECTIVE

Long-term effects of diet beverage consumption on the regulation of caloric intake is unclear. The goal of this study was to investigate whether the chronic intake of a liquid diet with nonnutritive sweeteners (NNS) would lead to greater appetite and weight gain.

METHODS

Wistar rats were fed a liquid diet (Osmolite) sweetened with nutritive sweetener (NS; sucrose) and NNS (stevia and saccharin) or a nonsweetened control. Intakes and weight gain were measured. Phases 1 and 2 investigated sweetness preference, phase 3 used diets with or without sweeteners, and phase 4 measured the effect on volume of food and caloric intake of alternating between NNS, NS, and control diets.

RESULTS

In phase 1, rats preferred: stevia, 0.10%; saccharin, 0.20%; and sucrose, 15%. In phase 2, rats preferred the sweetened diet over the control. In phase 3, rats fed the NS diet consumed less volume and more calories but gained less weight. In phase 4, when altering diet from NNS to NS, no differences were observed in appetite or weight gain.

CONCLUSIONS

Using sucrose-sweetened diet as a control, increased weight gain with the ingestion of NNS was observed. However, using a nonsweetened control, neither increased caloric intake nor weight gain occurred with NNS intake. Alternating diets between NNS, NS, and control did not affect the appetite.

Long-term intake of saccharin decreases post-absortive energy expenditure at rest and is associated to greater weight gain relative to sucrose in wistar rats

Background

Non-nutritive sweeteners (NNS) have been associated with increased prevalence of obesity. In previous studies, we demonstrated that saccharin could induce an increase in weight gain either when compared to sucrose or to a non-sweetened control at a similar total caloric intake. These data raised the hypothesis that reduced energy expenditure (EE) could be a potential mechanism explaining greater weight gain with saccharin use in rats. The aim of the present study was to compare long-term energy expenditure at rest between rats using saccharin or sucrose and correlate it with weight gain. 

Methods

In the present study, we examine the potential impact of saccharin compared to sucrose in the EE of Wistar rats. In a controlled experiment of 17 weeks, 24 Wistar rats were divided into 2 groups: saccharin-sweetened yogurt (SAC) or sucrose-sweetened yogurt (SUC), plus a free chow diet. Only rats that consumed at least 70% of the offered yogurt were included. EE (kcal/day) was determined at rest through open circuit indirect calorimetry system in the early post-absorptive period with determinations of both VO₂ consumption and CO₂ production. Measurements were evaluated at baseline, 5 and 12 weeks of dietary intervention. Weight gain, caloric intake (from yogurt, from chow and total) were determined weekly.

Results

Body weight and EE were similar between groups at baseline: (p = .35) and (p = .67) respectively. At the end of the study, SAC increased total weight gain significantly more in relation to SUC (p = .03). Cumulative total caloric intake (yogurt plus chow) was similar between groups during the whole period (p = .54). At 12 weeks, the EE was smaller in SAC compared to SUC (p = .009). Considering both groups, there was a strong negative correlation between total weight gain and change in EE observed [r(20) = −.61, p = .003]. However, when analyzing the groups separately we found that SUC maintained this inverse correlation [r(8) = −.68, p = .03], while SAC did not [r(10) = −.33, p = .29].

Conclusion

These data support the hypothesis that long-term use of saccharin may blunt post-absorptive EE at rest in Wistar rats, which is related to weight gain. On the other hand, long-term sucrose intake can increase energy expenditure in rats. This effect combined can explain, at least partially, the weight gain increases associated to saccharin in relation to sucrose in these animals.

The role of artificial and natural sweeteners in reducing the consumption of table sugar: A narrative review

The rapid increase in the prevalence of obesity worldwide has been partially attributed to the overconsumption of added sugars. Recent guidelines call for limiting the consumption of simple sugars to less than 10% of daily caloric consumption. High intensity sweeteners are regulated as food additives and include aspartame, acesulfame-k, neotame, saccharin, sucralose, cyclamate and alitame. Steviol glycosides and Luo Han Guo fruit extracts are high intensity sweeteners that are designated as generally recognized as safe (GRAS). Commonly used non-caloric artificial sweeteners may have unfavorable effect on health including glucose intolerance and failure to cause weight reduction. The nutritive sweeteners include sugar alcohols such as sorbitol, xylitol, lactitol, mannitol, erythritol, trehalose and maltitol. Naturally occurring rare sugars have recently emerged as an alternative category of sweeteners. These monosaccharides and their derivatives are found in nature in small quantities and lack significant calories. This category includes d-allulose (d-psicose), d-tagatose, d-sorbose and d-allose. Limiting consumption of any sweetener may well be the best health advice. Identifying natural sweeteners that have favorable effects on body weight and metabolism may help achieving the current recommendations of restricting simple sugar consumption.

EffectS of non-nutritive sWeetened beverages on appetITe during aCtive weigHt loss (SWITCH): Protocol for a randomized, controlled trial assessing the effects of non-nutritive sweetened beverages compared to water during a 12-week weight loss period and a follow up weight maintenance period

BACKGROUND

Acute and medium-term intervention studies suggest that non-nutritive sweeteners (NNS) are beneficial for weight loss, however there is limited human data on the long-term effects of consuming NNS on weight loss, maintenance, and appetite. Further research is therefore required to elucidate the prolonged impact of NNS consumption on these outcome measures.

METHODS/DESIGN

A randomized parallel groups design will be used to assess whether regular NNS beverage intake is equivalent to a water control in promoting weight loss over 12-weeks (weekly weight loss sessions; Phase I), then supporting weight maintenance over 40-weeks (monthly sessions; Phase II) and subsequently independent weight maintenance over 52-weeks (Phase III) in 432 participants. A subset of these participants (n=116) will complete laboratory-based appetite probe days (15 sessions; 3 sessions each at baseline, at the start of phase I and the end of each phase). A separate subset (n=50) will complete body composition scans (DXA) at baseline and at the end of each phase. All participants will regularly be weighed and will complete questionnaires and cognitive tasks to assess changes in body weight and appetitive behaviours. Measures of physical activity and biochemical markers will also be taken.

DISCUSSION

The trial will assess the efficacy of NNS beverages compared to water during a behavioural weight loss and maintenance programme. We aim to understand whether the impact of NNS on weight, dietary adherence and well-being are beneficial or transient and effects on prolonged successful weight loss and weight maintenance through sustained changes in appetite and eating behaviour.

TRIAL REGISTRATION

Clinical Trials: NCT02591134; registered: 23.10.2015.

Alterations in behaviour, cerebral cortical morphology and cerebral oxidative stress markers following aspartame ingestion

OBJECTIVE

The study evaluated changes in open field behaviours, cerebral cortical histomorphology and biochemical markers of oxidative stress following repeated administration of aspartame in mice.

METHODOLOGY

Adult mice were assigned into five groups of twelve each. Vehicle (distilled water), or aspartame (20, 40, 80 and 160mg/kg body weight) were administered orally for 28days. Horizontal locomotion, rearing and grooming were assessed after the first and last dose of aspartame. Sections of the cerebral cortex were processed and stained for general histology, and also examined for neuritic plaques using the Bielschwosky's protocol. Glial fibrillary acidic protein (GFAP) and neuron specific enolase (NSE) immunoreactivity were assessed using appropriate antibodies. Aspartate and antioxidant levels were also assayed from cerebral cortex homogenates. Data obtained were analysed using descriptive and inferential statistics.

RESULTS

Body weight and food consumption decreased significantly with aspartame consumption. Locomotion, rearing and grooming increased significantly after first dose, and with repeated administration of aspartame. Histological changes consistent with neuronal damage were seen at 40, 80 and 160mg/kg. Neuritic plaque formation was not evident; while GFAP-reactive astrocytes and NSE-reactive neurons increased at 40 and 80mg/kg but decreased at 160mg/kg. Superoxide dismutase and nitric oxide increased with increasing doses of aspartame, while aspartate levels showed no significant difference.

CONCLUSION

The study showed morphological alterations consistent with neuronal injury and biochemical changes of oxidative stress. These data therefore supports the need for caution in the indiscriminate use of aspartame as a non-nutritive sweetener.

Sucralose Promotes Food Intake through NPY and a Neuronal Fasting Response

Non-nutritive sweeteners like sucralose are consumed by billions of people. While animal and human studies have demonstrated a link between synthetic sweetener consumption and metabolic dysregulation, the mechanisms responsible remain unknown. Here we use a diet supplemented with sucralose to investigate the long-term effects of sweet/energy imbalance. In flies, chronic sweet/energy imbalance promoted hyperactivity, insomnia, glucose intolerance, enhanced sweet taste perception, and a sustained increase in food and calories consumed, effects that are reversed upon sucralose removal. Mechanistically, this response was mapped to the ancient insulin, catecholamine, and NPF/NPY systems and the energy sensor AMPK, which together comprise a novel neuronal starvation response pathway. Interestingly, chronic sweet/energy imbalance promoted increased food intake in mammals as well, and this also occurs through an NPY-dependent mechanism. Together, our data show that chronic consumption of a sweet/energy imbalanced diet triggers a conserved neuronal fasting response and increases the motivation to eat.

Artificial sweeteners and metabolic dysregulation: Lessons learned from agriculture and the laboratory

Escalating rates of obesity and public health messages to reduce excessive sugar intake have fuelled the consumption of artificial sweeteners in a wide range of products from breakfast cereals to snack foods and beverages. Artificial sweeteners impart a sweet taste without the associated energy and have been widely recommended by medical professionals since they are considered safe. However, associations observed in long-term prospective studies raise the concern that regular consumption of artificial sweeteners might actually contribute to development of metabolic derangements that lead to obesity, type 2 diabetes and cardiovascular disease. Obtaining mechanistic data on artificial sweetener use in humans in relation to metabolic dysfunction is difficult due to the long time frames over which dietary factors might exert their effects on health and the large number of confounding variables that need to be considered. Thus, mechanistic data from animal models can be highly useful because they permit greater experimental control. Results from animal studies in both the agricultural sector and the laboratory indicate that artificial sweeteners may not only promote food intake and weight gain but can also induce metabolic alterations in a wide range of animal species. As a result, simple substitution of artificial sweeteners for sugars in humans may not produce the intended consequences. Instead consumption of artificial sweeteners might contribute to increases in risks for obesity or its attendant negative health outcomes. As a result, it is critical that the impacts of artificial sweeteners on health and disease continue to be more thoroughly evaluated in humans.

Not-so-healthy sugar substitutes?

Replacing sugar-sweetened beverages with diet soft drinks containing sugar substitutes that provide few or no calories has been suggested as one strategy for promoting improved public health outcomes. However, current scientific evidence indicates that routine consumption of beverages with non-nutritive sweeteners not only fails to prevent disease, but is associated with increases in risks for the same health outcomes associated with sugar-sweetened beverages, including type 2 diabetes, cardiovascular disease, hypertension and stroke. Results from pre-clinical studies have provided plausible biological mechanisms that could promote these counterintuitive negative health effects of artificial sweeteners. Taken together, scientific studies currently indicate that public health will be improved by reducing intake of all sweeteners, both caloric and non-caloric.

Sweetening yoghurt with glucose, but not with saccharin, promotes weight gain and increased fat pad mass in rats

The claim that non-nutritive sweeteners accelerate body weight gain by disrupting sweet-calorie associations was tested in two experiments using rats. The experiments were modelled on a key study from a series of experiments reporting greater body weight gain in rats fed yoghurt sweetened with saccharin than with glucose (Swithers & Davidson, 2008). Both of the current experiments likewise compared groups fed saccharin- or glucose-sweetened yoghurt in addition to chow and water, while Experiment 1 included a third group (Control) given unsweetened yoghurt. In Experiment 1, but not in Experiment 2, rats were initially exposed to both saccharin- and glucose-sweetened yoghurts to assess their relative palatability. We also tested whether the provision of an energy-dense sweet biscuit would augment any effects of saccharin on food intake and weight gain, as seemingly predicted by Swithers and Davidson (2008). In Experiment 1 there were no differences in body weight gain or fat pad mass between the Saccharin and Control group, whereas the Glucose group was the heaviest by the final 5 weeks and at cull had the largest fat pads. Greater acceptance of saccharin predicted more weight gain over the whole experiment. Consistent with past reports, fasting blood glucose and insulin measures did not differ between the Saccharin and Control groups, but suggested some impairment of insulin sensitivity in the Glucose group. Experiment 2 found similar effects of glucose on fat mass, but not on body weight gain. In summary, adding saccharin had no detectable effects on body-weight regulation, whereas the effects of glucose on fat pad mass were consistent with previous studies reporting more harmful effects of sugars compared to non-nutritive sweeteners.

Low-calorie sweetener use and energy balance: Results from experimental studies in animals, and large-scale prospective studies in humans

For more than a decade, pioneering animal studies conducted by investigators at Purdue University have provided evidence to support a central thesis: that the uncoupling of sweet taste and caloric intake by low-calorie sweeteners (LCS) can disrupt an animal's ability to predict the metabolic consequences of sweet taste, and thereby impair the animal's ability to respond appropriately to sweet-tasting foods. These investigators' work has been replicated and extended internationally. There now exists a body of evidence, from a number of investigators, that animals chronically exposed to any of a range of LCSs - including saccharin, sucralose, acesulfame potassium, aspartame, or the combination of erythritol+aspartame - have exhibited one or more of the following conditions: increased food consumption, lower post-prandial thermogenesis, increased weight gain, greater percent body fat, decreased GLP-1 release during glucose tolerance testing, and significantly greater fasting glucose, glucose area under the curve during glucose tolerance testing, and hyperinsulinemia, compared with animals exposed to plain water or - in many cases - even to calorically-sweetened foods or liquids. Adverse impacts of LCS have appeared diminished in animals on dietary restriction, but were pronounced among males, animals genetically predisposed to obesity, and animals with diet-induced obesity. Impacts have been especially striking in animals on high-energy diets: diets high in fats and sugars, and diets which resemble a highly-processed 'Western' diet, including trans-fatty acids and monosodium glutamate. These studies have offered both support for, and biologically plausible mechanisms to explain, the results from a series of large-scale, long-term prospective observational studies conducted in humans, in which longitudinal increases in weight, abdominal adiposity, and incidence of overweight and obesity have been observed among study participants who reported using diet sodas and other LCS-sweetened beverages daily or more often at baseline. Furthermore, frequent use of diet beverages has been associated prospectively with increased long-term risk and/or hazard of a number of cardiometabolic conditions usually considered to be among the sequelae of obesity: hypertension, metabolic syndrome, diabetes, depression, kidney dysfunction, heart attack, stroke, and even cardiovascular and total mortality. Reverse causality does not appear to explain fully the increased risk observed across all of these studies, the majority of which have included key potential confounders as covariates. These have included body mass index or waist circumference at baseline; total caloric intake and specific macronutrient intake; physical activity; smoking; demographic and other relevant risk factors; and/or family history of disease. Whether non-LCS ingredients in diet beverages might have independently increased the weight gain and/or cardiometabolic risk observed among frequent consumers of LCS-sweetened beverages deserves further exploration. In the meantime, however, there is a striking congruence between results from animal research and a number of large-scale, long-term observational studies in humans, in finding significantly increased weight gain, adiposity, incidence of obesity, cardiometabolic risk, and even total mortality among individuals with chronic, daily exposure to low-calorie sweeteners - and these results are troubling.

Does low-energy sweetener consumption affect energy intake and body weight? A systematic review, including meta-analyses, of the evidence from human and animal studies

By reducing energy density, low-energy sweeteners (LES) might be expected to reduce energy intake (EI) and body weight (BW). To assess the totality of the evidence testing the null hypothesis that LES exposure (versus sugars or unsweetened alternatives) has no effect on EI or BW, we conducted a systematic review of relevant studies in animals and humans consuming LES with ad libitum access to food energy. In 62 of 90 animal studies exposure to LES did not affect or decreased BW. Of 28 reporting increased BW, 19 compared LES with glucose exposure using a specific ‘learning' paradigm. Twelve prospective cohort studies in humans reported inconsistent associations between LES use and body mass index (−0.002 kg m⁻² per year, 95% confidence interval (CI) −0.009 to 0.005). Meta-analysis of short-term randomized controlled trials (129 comparisons) showed reduced total EI for LES versus sugar-sweetened food or beverage consumption before an ad libitum meal (−94 kcal, 95% CI −122 to −66), with no difference versus water (−2 kcal, 95% CI −30 to 26). This was consistent with EI results from sustained intervention randomized controlled trials (10 comparisons). Meta-analysis of sustained intervention randomized controlled trials (4 weeks to 40 months) showed that consumption of LES versus sugar led to relatively reduced BW (nine comparisons; −1.35 kg, 95% CI –2.28 to −0.42), and a similar relative reduction in BW versus water (three comparisons; −1.24 kg, 95% CI –2.22 to −0.26). Most animal studies did not mimic LES consumption by humans, and reverse causation may influence the results of prospective cohort studies. The preponderance of evidence from all human randomized controlled trials indicates that LES do not increase EI or BW, whether compared with caloric or non-caloric (for example, water) control conditions. Overall, the balance of evidence indicates that use of LES in place of sugar, in children and adults, leads to reduced EI and BW, and possibly also when compared with water.

Non-caloric artificial sweeteners and the microbiome: findings and challenges

Non-caloric artificial sweeteners (NAS) are common food supplements consumed by millions worldwide as means of combating weight gain and diabetes, by retaining sweet taste without increasing caloric intake. While they are considered safe, there is increasing controversy regarding their potential ability to promote metabolic derangements in some humans. We recently demonstrated that NAS consumption could induce glucose intolerance in mice and distinct human subsets, by functionally altering the gut microbiome. In this commentary, we discuss these findings in the context of previous and recent works demonstrating the effects of NAS on host health and the microbiome, and the challenges and open questions that need to be addressed in understanding the effects of NAS consumption on human health.

Adding Molecules to Food, Pros and Cons: A Review on Synthetic and Natural Food Additives

The pressing issue to feed the increasing world population has created a demand to enhance food production, which has to be cheaper, but at the same time must meet high quality standards. Taste, appearance, texture, and microbiological safety are required to be preserved within a foodstuff for the longest period of time. Although considerable improvements have been achieved in terms of food additives, some are still enveloped in controversy. The lack of uniformity in worldwide laws regarding additives, along with conflicting results of many studies help foster this controversy. In this report, the most important preservatives, nutritional additives, coloring, flavoring, texturizing, and miscellaneous agents are analyzed in terms of safety and toxicity. Natural additives and extracts, which are gaining interest due to changes in consumer habits are also evaluated in terms of their benefits to health and combined effects. Technologies, like edible coatings and films, which have helped overcome some drawbacks of additives, but still pose some disadvantages, are briefly addressed. Future trends like nanoencapsulation and the development of "smart" additives and packages, specific vaccines for intolerance to additives, use of fungi to produce additives, and DNA recombinant technologies are summarized.

An application of Pavlovian principles to the problems of obesity and cognitive decline

An enormous amount of research has been aimed at identifying biological and environmental factors that are contributing to the current global obesity pandemic. The present paper reviews recent findings which suggest that obesity is attributable, at least in part, to a disruption of the Pavlovian control of energy regulation. Within our framework, this disruption occurs when (a) consumption of sweet-tasting, but low calorie or noncaloric, foods and beverages reduces the ability of sweet tastes to predict the postingestive caloric consequences of intake and (b) consuming diets high in saturated fat and sugar (a.k.a., Western diet) impairs hippocampal-dependent learning and memory processes that are involved with the use of interoceptive "satiety" signals to anticipate when food and eating are not followed by appetitive postingestive outcomes. The paper concludes with discussion of a "vicious-cycle" model which links obesity to cognitive decline.

Effects of a nonnutritive sweetener on body adiposity and energy metabolism in mice with diet-induced obesity

OBJECTIVE

Nonnutritive sweeteners (NNSs) have been studied in terms of their potential roles in type 2 diabetes, obesity, and related metabolic disorders. Several studies have suggested that NNSs have several specific effects on metabolism such as reduced postprandial hyperglycemia and insulin resistance. However, the detailed effects of NNSs on body adiposity and energy metabolism have not been fully elucidated. We investigated the effects of an NNS on energy metabolism in mice with diet-induced obesity (DIO).

METHODS

DIO mice were divided into NNS-administered (4% NNS in drinking water), sucrose-administered (33% sucrose in drinking water), and control (normal water) groups. After supplementation for 4 weeks, metabolic parameters, including uncoupling protein (UCP) levels and energy expenditure, were assessed.

RESULTS

Sucrose supplementation increased hyperglycemia, body adiposity, and body weight compared to the NNS-administered and control groups (P<0.05 for each). In addition, NNS supplementation decreased hyperglycemia compared to the sucrose-administered group (P<0.05). Interestingly, NNS supplementation increased body adiposity, which was accompanied by hyperinsulinemia, compared to controls (P<0.05 for each). NNS also increased leptin levels in white adipose tissue and triglyceride levels in tissues compared to controls (P<0.05 for each). Notably, compared to controls, NNS supplementation decreased the UCP1 level in brown adipose tissue and decreased O2 consumption in the dark phase.

CONCLUSIONS

NNSs may be good sugar substitutes for people with hyperglycemia, but appear to influence energy metabolism in DIO mice.

Incubation of saccharin craving and within-session changes in responding for a cue previously associated with saccharin

Time-dependent increases in cue-induced sucrose seeking after forced abstinence have been described in rats with a history of sucrose self-administration, suggesting sucrose craving "incubates". In the present study, we examined whether the incubation of craving generalizes to the artificial sweetener, saccharin. Thirty-one male Long-Evans rats lever pressed for 0.3% saccharin solution 1h/day for 10 days. On either Day 1 or 30 of forced abstinence, rats responded for 1h for presentation of a tone+light cue previously presented with every saccharin delivery during self-administration training. Rats responded more during this cue-reactivity test session following 30 vs. 1 day of forced abstinence ("incubation of craving"). This result is the first demonstration of the "incubation of saccharin craving" and suggests that a post-ingestive caloric consequence of self-administration is not a necessary condition for the development of incubation of sucrose craving. We also examined the time course (within-session decreases) of active-lever responding during the 1-h cue-reactivity test session. Rats in the Day 30 group responded more than rats in the Day 1 group from the beginning of the test session. In addition, within-session decreases in responding were shallower in slope in the Day 30 than the Day 1 group. These results indicate that "incubation of saccharin craving" enhances the persistence of seeking behavior.

Artificial sweeteners produce the counterintuitive effect of inducing metabolic derangements

The negative impact of consuming sugar-sweetened beverages on weight and other health outcomes has been increasingly recognized; therefore, many people have turned to high-intensity sweeteners like aspartame, sucralose, and saccharin as a way to reduce the risk of these consequences. However, accumulating evidence suggests that frequent consumers of these sugar substitutes may also be at increased risk of excessive weight gain, metabolic syndrome, type 2 diabetes, and cardiovascular disease. This paper discusses these findings and considers the hypothesis that consuming sweet-tasting but noncaloric or reduced-calorie food and beverages interferes with learned responses that normally contribute to glucose and energy homeostasis. Because of this interference, frequent consumption of high-intensity sweeteners may have the counterintuitive effect of inducing metabolic derangements.