Zero-calorie sweeteners, such as Splenda (sucralose), Sweet’N Low (saccharin), and NutraSweet (aspartame) are commonly used as alternatives to digestible, high energy-yielding sugars in order to flavor foods and drinks. However, recent studies are finding an association between the ingestion of artificial sweeteners and the simultaneous rise in body fat percentages of those taking in the substances. This begs the question we intend to take a closer look at: are zero-calorie sweeteners making us fatter through an unintended counter-effect of increasing body fat to those who consume larger amounts of it? And if so, can we shed some light on how this mechanism might work? Moreover, to explain this ostensible paradox we’ll explore the concept of zero-calorie sweeteners and why they are, in theory, metabolically unavailable to us as energy substrates.
The majority of non-nutritive sweeteners (NNS) are more than several hundred times as sweet as sucrose, the disaccharide composed of glucose and fructose (α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside) known as table sugar. This is due to their affinity to bind extremely tightly to the G-protein coupled receptors for sweetness on the human tongue, which subsequently trigger continuing chemical signaling to the brain we perceive as a “sweet” taste. However, unlike our ability to catabolize sucrose, humans do not possess the enzymes necessary to break down the many different molecular structures of non-nutritive sweeteners such that we are unable to harness the bonding energies present in the molecules, and thus they are unavailable to humans as energy substrates as their general name of “non-nutritive sweeteners” suggests.
Several current studies are beginning to show that non-nutritive sweetener effects do not simply end at receptors on the tongue without a caloric effect, as was once previously thought. Many studies involving both animals and humans have found a simultaneous rise in adiposity (among several other deleterious health effects) along with NNS consumption, an especially alarming trend due to the popularity of NNS and their reputation as a way to circumvent excess calories and ultimately lose weight. This association and ubiquity of artificial sweeteners makes further research in this area of utmost relevance to consumers worldwide.
Though a host of hypotheses exist surrounding NNS and their bodily effects, many of which are unfounded proposals by self-appointed authorities, there are a few that have actually gained significant traction in the scientific community. One such suggested mechanism is that daily ingestion of NNS may interfere with the predictive relation between sweet taste and calories, which subsequently, may impair energy balance by suppressing Glucagon-like peptide (GLP)-1 release, which could alter glucose homeostasis and reduce satiety. GLP-1 stimulates the release of insulin and inhibits the release of glucagon, both of which lead to the lowering of blood glucose. Moreover, other studies suggest there are sweetness receptors in the gut that artificial sweeteners can bind to. When this occurs, several physiological responses mimic those expected in the case of sugar binding to the same receptors including the uptake of glucose, and the release of digestive hormones throughout the digestive tract. These bodily responses indicate that ingestion of NNS have effectively fooled your receptors at both the points of consumption (mouth) and digestion. This may result in the disruption of the body’s ability to ascertain whether a given quantity of food is sufficient to meet energy demands. In order to combat this confused state of satiety, the body may begin prompting one to consume more total calories in order to satisfy energy needs, thereby resulting in increased weight gain and overall negation of sugar substitutes.
The results found in these many studies make a case that consumption of natural sugars in moderate quantities may be more compatible with weight-loss or weight management than do non-nutritive artificial sweeteners. This is not to say NNS are not effective as a way to occasionally bypass sugar-laden food and drink as they are generally considered safe on a limited basis, however, it may not be the optimal choice for those who have undisciplined dietary habits and believe replacement of sugars with NNS will result in losing fat.