Monday, October 17, 2011

Diet Drinks: They Are NOT What You Thought They Were

I.  Introduction
II.  Artificial Sweeteners and Weight Gain
III. Artificial Sweeteners, Appetite, and the Food Reward System
IV. Artificial Sweeteners and Adverse Events?  Still Unclear
V. Dr. O's Final Thoughts
VI. References
I.  Introduction
And what did you think they were?  Healthy.  You thought they help you lose weight.  You thought these products were made for health conscious people.  And the media/marketing machines have worked to perfection.  Historically, women have been the main consumers of diet sodas.  Now, these drinks are being re-branded as “Such & Such” Zero, packaged in “manly” colors (i.e. – black), and now more than ever, more men are consuming these drinks.  In reality, NO health conscious person should be drinking diet drinks.  The artificial sweetener, aspartame, is the major ingredient found in diet sodas, Equal, and NutraSweet.  It provides the sweet taste without the calories.  Other commonly used artificial sweeteners include saccharin, acesulfame-K, and sucralose (Splenda).  I know a lot of people say that diet drinks make you crave sweet even more.  Well, for the people who don't believe that, I'm here to share scientific studies that might change your mind.  Many studies have shown that aspartame, and artificial sweeteners in general, make it harder for you to lose weight and increase sugar cravings.   
II. Artificial Sweeteners and Weight Gain
     A. Epidemiological Studies

Epidemiological studies suggest that artificial sweetener and diet soda consumption can contribute to weight gain.  In a study by Fowler et al. (2008), 5,158 adults from San Antonio, Texas were measured for their height, weight, BMI, and artificially sweetened beverage (ASB) consumption (baseline).  ASBs included diet drinks, sweetened coffee, and sweetened tea.  Seven to eight years later (follow-up), 3,682 of those residents were re-examined for incidence of being overweight, obesity, and change in BMI. 

Normal weight individuals who reported drinking less than 3 artificially-sweetened beverages per week at baseline and at follow-up were 1.5 times more likely to be overweight or obese at the 7-8 year follow-up than those who did not drink ASBs.  Those reporting 3-21 ASBs per week were 1.75 times more likely to be overweight or obese.  Those reporting 22+ ASBs per week were 2 times more likely to be overweight or obese.  Also, individuals who reported drinking 3+ ASBs per week also had significantly higher BMIs.  This data does not suggest that sweeteners are the main cause of these changes.  However, there is clearly a “positive dose-response relationship” between ASB consumption and weight gain. 

Even more disturbing, this relationship also exists with children.  Forshee et al., (2003) conducted “descriptive and multivariate regression analysis of children aged 6-19 from the US Department of Agriculture’s Continuing Survey of Food Intake by Individuals”.  Results suggest that the consumption of diet carbonated drinks (aspartame) positively correlates with an increase in BMI.

A similar study by Nettleton et al. (2009) also showed that diet soda (aspartame) consumption positively correlates with metabolic syndrome and type 2 diabetes among those who participated in in the Multi-Ethnic Study of Atherosclerosis.

     B.  “So how do artificial sweeteners actually make you fatter and put you at greater risk??”

One answer may lie in the amount of calories that people consume during the day while drinking a “diet” drink.  Simply put, in the mind of some, diet drinks free up calories to be consumed from other sources.  You know, the “I drank all diet drinks today, so I’ll eat some ice cream to reward myself” type of people.  This lack of discipline and the intake of the wrong foods results in caloric intake above one’s weight maintenance level, malnutrition, and fat gain.  Artificial sweeteners themselves don’t make you fatter, but they give a false sense of comfort, which can make you more willing to make the wrong decisions in your diet.  Let’s be clear: DIET DRINKS DON’T DO MAGIC!  Caloric restriction, proper nutrition, and exercise are the only ways to lose weight.  Just drinking diet drinks will not help or speed up the process. 

A study by Knopp et al. (1976) showed that aspartame does not speed up weight loss.  This study assessed the effect of aspartame (2.7g/day for 13 weeks) in combination with a calorie-restricted diet (1000 calories/day) on subject with a mean age of 19.3 years, mean body weight of 164.6 lb, mean height of 65.4 in and 33% in excess of ideal body weight.  There was no significant difference in weight loss between the aspartame group and the placebo group.  Also, changes in glucose, immunoreactive insulin, and immunoreactive glucagon were characteristic of a calorie restriction, suggesting that aspartame played no role in weight loss.

This was also shown by Blackburn et al. (1997), who randomly assigned 163 obese women to a 19-week weight loss program which either allowed or avoided aspartame-sweetened foods and beverages for 16 weeks.  Dieticians guided subjects on nutrition and exercise.  The no-aspartame group was encouraged to use sugar and/or honey as sweeteners.  Subjects were instructed to complete 200 min of aerobic exercise per week; however, no details were provided on caloric intake during this weight loss program.  The authors state that “The same group leader led both groups (aspartame group and sugar/honey group) to ensure uniform treatment”.  I have no idea if that means equal caloric intake or not.  But the main point is that this weight loss program resulted in similar weight loss in both the aspartame and no-aspartame group. 
III. Artificial Sweeteners, Appetite, and the Food Reward System

I know what some are thinking:  “Well duh! As long as I reduce my calories, eat the right foods, then I can still drink diet drinks to scratch my soda/fruit drink itch and lose weight!”  Not so fast, my friend! 

While you can still lose weight, several issues remain.  Studies suggest that artificial sweeteners increase human appetite.  Black et al. (1992) showed that subjective appetite through the day was significantly higher in patients who consumed 280 ml of carbonated mineral water sweetened with 340 mg aspartame vs. subjects who consumed 280 ml of unsweetened carbonated mineral water.  So while it is possible to lose weight while consuming aspartame, you are making it more difficult for yourself by consuming artificially sweetened drinks.  Interestingly, this study also showed that consuming 280 ml of carbonated mineral water with 340 mg aspartame in capsule form did not increase subjective appetite.  This result suggests that the actual tasting of aspartame induces the increased appetite. 

This begs the question: What response occurs on the tongue that causes increased appetite?  The answer may involve the neurological responses to glucose versus artificial sweetener consumption.

To gain a better understanding of the “increased appetite” response, it is important to have a general understanding of the food reward system, which is a part of your nervous system.  Your taste buds are a part of your food reward system, where taste receptors ascend through the thalamus and into the cerebral cortex.  I won’t go into great detail about the neuroanatomy, but one important note is that dopamine, the “reward” neurotransmitter, is crucial in facilitating the reward response in the brain from taste receptors and signaling satisfaction, or in this case, quenching your sugar craving.

So, with that background, let’s dig into the research.  Studies have shown that artificial sweeteners do not activate the food reward system in the same way as natural sweeteners.  A study by Smeets et al. (2003) used functional MRI to illustrate that consuming aspartame-sweetened beverages does not induce the same response as glucose-sweetened beverages in the hypothalamus, the part of the brain that releases dopamine and regulates hunger.  Glucose-sweetened beverages induced a significant, prolonged decrease in hypothalamic activity, while aspartame-sweetened beverages did not.  So, while you taste something sweet with a diet drink, your food reward system may not actually recognize it since it is artificial.  Therefore, the demand for sweets in your hypothalamus will not decrease (as it would with natural sweets).  What’s the result? 

You asking yourself why you’re still craving sweets after drinking diet drinks all day.  This may cause you to binge more and more on sweets OR fight with your cravings all day and night, making you go crazy.  Sound familiar?

Furthermore, while natural and artificial sweeteners bind to the same sweet taste receptors, they do not bind in the same way (Morini et al., 2005).  This binding difference may also play a role in the altered brain response to artificial sweetener consumption.
IV. Artificial Sweeteners and Adverse Events?  Still Unclear

Many studies have investigated the development of adverse reactions associated with artificial sweeteners.  Unfortunately, these studies present conflicting results.  Some individuals have reported headaches, dizziness, or gastrointestinal discomfort from artificial sweetener consumption, while others have not.  At this point, a definitive answer is not available.  However, I’m sure that further research will provide answers.  Animal studies are useful in providing insight into how artificial sweeteners might affect the body.  But no conclusions about humans can be made from animal studies.  Therefore, there is a limit on how much data can be acquired from human subjects. 
V. Dr. O's Final Thoughts

What we do know is that artificially sweeteners do not stimulate the same brain response as natural sweeteners.  Studies suggest that artificial sweeteners may not stimulate the food reward system effectively, resulting in the maintenance of sugar cravings.  Long-term adverse events from artificially sweetener consumption have been reported, but studies have presented conflicting results.  However, in regards to weight loss, it is clear that diet sodas make it harder to lose weight.  Here's the hypothesized chain of events:

1.  Artificially sweetener binds to taste receptors in an unnatural way.
2.  Binding induces stimuli to the brain that is different from natural sweets.
3.  The reward center in the brain (hypothalamus) does not receive the normal "sweets have been eaten, I don't need them anymore" signal.
4.  You still crave sweets.

Then the following could happen:

5.  You drink more "Diet Such & Such Zero"
6.  You still crave sweets.
7.  You drink more "Diet Such & Such Zero"
8.  You still crave sweets.
71.  You drink more "Diet Such & Such Zero" 
72.  You still crave sweets.
73.  You give in and go on a sweets binge.

Yes, extreme...but you get the point.  Stop drinking diet drinks.

Dr. O 
"I don't live to eat...I eat to live!"
VI. References

1.    Black, R.M., L.A. Leiter, and G.H. Anderson, Consuming aspartame with and without taste: differential effects on appetite and food intake of young adult males. Physiol Behav, 1993. 53(3): p. 459-66.

2.    Blackburn, G.L., et al., The effect of aspartame as part of a multdisciplinary weight-control program on short- and long-term control of body weight. Am J Clin Nutr, 1997. 65: p. 409-418.

3.    Forshee, R.A. and M.L. Storey, Total beverage consumption and beverage choices among children and adolescents. Int J Food Sci Nutr, 2003. 54(4): p. 297-307.

4.    Fowler, S.P., et al., Fueling the Obesity Epidemic?  Artificially Sweetened Beverage Use and Long-term Weight Gain. Obesity, 2008. 16: p. 1894-1900.

5.    Knopp, R.H., K. Brandt, and R.A. Arky, Effects of aspartame in young persons during weight reduction. J Toxicol Environ Health, 1976. 2(2): p. 417-428.

6.    Morini, G., A. Bassoli, and P.A. Temussi, From Small Sweeteners to Sweet Proteins: Anatomy of the Binding Sites of the Human T1R2_T1R3 Receptor. J Med Chem, 2005. 48: p. 5520-5529.

7.    Nettleton, J.A., et al., Diet Soda Intake and Risk of Incident Metabolic Syndrome and Type 2 Diabetes in the Multi-Ethnic Study of Atherosclerosis (MESA). Diabetes Care, 2009. 32: p. 688-694.

8.    Smeets, P.A.M., et al., Functional magnetic resonance imaging of human hypothalamic responses to sweet taste and calories. Am J Clin Nutr, 2005. 82: p. 1011-1016.

9.    Yang, Q., Gain weight by "going diet?"  Artificial sweeteners and the neurobiology of sugar cravings. Yale J Bio Med, 2010. 83: p. 101-108.


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