Diet Soda is Not A Free Ride

There is little doubt that obesity in America is on the upswing. Lots of people think that an artificially-sweetened beverage can offset the poor dietary decisions to which they have become accustomed. There has been established a relationship between non-sugar sweeteners and weight gain based on physiological responses to the message of satiety and the perceived need to consume more calories to achieve it. While the perception of sweet taste is supposed to satisfy appetite, the calculated deception to the body just might boomerang and call off all bets.

In the San Antonio Heart Study that ran from 1979 to 1988, researchers examined the association of artificially sweetened beverages with long-term weight gain, and found that, “A significant positive dose-response relationship emerged between baseline ASB (artificially sweetened beverage) consumption and all outcome measures…”  These outcome measures included overweight / obesity, weight gain, and changes in body mass index (BMI).  As with most nutrition research, considerations were made for demographics and behavioral characteristics.  Drinking more than twenty-one ASB’s a week had the most impact, with “…almost double risk of overweight / obesity among 1,250 baseline normal-weight individuals.”  For those with a body mass index already elevated, the changes were more pronounced.  This report concluded with, “These findings raise the question whether AS (artificial sweetener) use might be fueling—rather than fighting—our escalating obesity epidemic.”

That last sentence from the San Antonio Heart Study is quite the incrimination, would you say? Diet soft drinks have long been thought to be healthier alternatives to their sugary counterparts, but reports like this one have linked increased incidence of weight gain, metabolic syndrome, and even diabetes to frequent intake of diet soft drinks.  Keep in mind, though, that all studies in all areas of health care are subject to scrutiny and critique.    Regardless of the topic, there are always two—or more—sides.  But here it may have been discovered that fooling the body is the instigator behind the concern.

When the body is told that something sweet has been ingested, it launches the production of insulin to carry the sweet to the cells to be burned for energy.  By the time the body finds out that there really is no sugar to be burned—in the form of glucose—the insulin has already been sent on its way to work.  Now the insulin has to find something to do, so it initiates a signal that says, “Feed me.  I need to carry glucose.”  That arouses hunger.  What do we grab for immediate satisfaction?  Carbohydrates, the simpler, the better.  Most of them spike glucose rapidly, which, if it fails to get burned for energy, is stored as fat.  It now appears that a lack of exercise becomes part of the equation.

There’s another tack to look at.  Some artificial sweeteners are alleged to block the brain’s production of serotonin, the neurotransmitter that controls mood, learning, sleep, and…appetite.  When the body experiences low levels of serotonin—and that can affect depressed mood—it seeks foods that can bring the levels back up.   Those foods happen to be the ones that will also bring the belt size up. Real sugar, of course, provides empty calories that can also cause weight gain as excessive energy intake.  But a weight conscious public does what it thinks is right.

Sweet taste enhances appetite.  Aspartame-sweetened water, for example, increased subjective hunger ratings when compared to glucose-sweetened water.  (Yang. 2010)  Other artificial sweeteners were associated with heightened motivation to eat, with more items selected on a food preference list. (Blundell. 1986)  This suggests that the calories in natural sweeteners trigger a response to keep overall energy intake constant, and that inconsistent coupling between sweet taste and actual caloric content can lead to compensatory overeating and consequential positive energy balance.  (This means that more energy came into the body than went out.)  People associate taste with calorie content.  You can tell that a crème brulee has more calories than the eggs from which it is made, but you’d probably eat more of it if made with artificial sweetener than with cane sugar.

Humans have a hedonic component.  We like those things that appeal to the senses and activate our food reward pathways.  That contributes to appetite increase.  But artificial sweeteners fail to provide completeness.  Unsweetening the American diet over the long haul, a little at a time, might just do the trick.  After all, it seems to work with salt.

MAIN ABSTRACT Obesity (2008) 16(8), 1894–1900. Fueling the Obesity Epidemic? Artificially Sweetened Beverage Use and Long-term Weight Gain Sharon P. Fowler, Ken Williams, Roy G. Resendez, Kelly J. Hunt, Helen P. Hazuda and Michael P. Stern

SUPPORTING ABSTRACTS Diabetes Care. 2009 Apr;32(4):688-94. Epub 2009 Jan 16. Diet soda intake and risk of incident metabolic syndrome and type 2 diabetes in the Multi-Ethnic Study of Atherosclerosis (MESA). Nettleton JA, Lutsey PL, Wang Y, Lima JA, Michos ED, Jacobs DR Jr. SourceDivision of Epidemiology, University of Texas Health Sciences Center, Houston, Texas, USA. jennifer.a.nettleton@uth.tmc.edu

Physiol Behav. 2010 Apr 26;100(1):55-62. Epub 2010 Jan 6. High-intensity sweeteners and energy balance. Swithers SE, Martin AA, Davidson TL. SourceDepartment of Psychological Sciences, Purdue University, 703 Third Street, West Lafayette, IN 47907, United States. swithers@purdue.edu

Yale J Biol Med. 2010 June; 83(2): 101–108. Gain weight by “going diet?” Artificial sweeteners and the neurobiology of sugar cravings Neuroscience 2010 Qing Yang

The Lancet, Volume 327, Issue 8489, 10 May 1986, Pages 1092-1093 PARADOXICAL EFFECTS OF AN INTENSE SWEETENER (ASPARTAME) ON APPETITE J. E. Blundell, A. J. Hill