Obesity Weekly

A weekly update about some aspect of Obesity. Published Monday mornings

Sugar Sweetened Beverages

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An increase in the consumption of sugar sweetened beverages (SSBs) in the past 30 years has been observed (1).  Since obesity rates have increased at the same time, the correlation does suggest a cause and effect relationship. (For a further discussion on correlations versus cause and effect click here).  Just because something happens together (correlates) and even if it makes sense to us, does not mean there is a cause and effect relationship (a)  Figuring out the cause of anything in free range humans is difficult because our lives are so complex.  In a lab you can have two groups of animals where you can change one thing while keeping all other things equal.  As easy as this sounds it still is difficult to implement because animals will change their behavior and confound your studies.  Try to do this with a large group of humans.  Many investigators have explored the correlation between increased consumption of SSBs and attempted to ascertain if the correlation is indeed a cause and effect relationship.  Some studies have demonstrated a strong correlation (2) while several others have suggested that the evidence is insufficient (3,4) (b).  Now just because the conclusion is reached that the evidence is insufficient doesn’t mean that it is evidence of not being an effect. I just means that the data being analyzed doesn’t give enough confidence to support the conclusion.

In a recently published study, one aspect of SSB consumption was tested, the effect of removing SSBs during diet and its effect on weight loss (5).  The power of the current study is the large number of subjects (810), length of time (18 months) and the rigorous analysis of caloric consumption by the subjects. It was also a propective study, not a retrospective study. The effects of other beverage consumption was assessed as well, diet drinks, juice, milk, coffee and tea (sweetened or unsweetened), and alcoholic beverages.  Four findings emerged from the study:  1)  Decreasing the number of calories consumed as SSBs had a positive effect on weight loss;  2)  the effect of liquid calorie reduction had a stronger effect on weight than a decrease in solid calorie intake; 3) a reduction in SSB had a positive effect on weight loss at both 6 and 18 months, and; 4) no other beverage (diet drinks, juice, milk or alcohol) was associated with weight change.  Decreasing SSB consumption by a serving per day was associated with about a one pound weight loss at 6 moths and a one and a-half pound loss at 18 months.  Other studies with milk had suggested a benefit on weight loss, presumably due to an increase in calcium intake.  These findings were not confirmed, but milk intake did not have an adverse effect on weight loss either.  The authors went on to speculate as to the mechanism(s) of the findings, recruitment of satiety effects for milk, ease of oxidation as a fuel for alcohol.  It would be good to know why the effects of SSBs are observed, but the data are convincing, decrease the intake of SSBs and you will have a positive effect on weight loss.  So of all the things to change during a diet, decreasing the intake of full calorie beverages should be simple to implement and have a good effect on body weight (c,d).

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Interesting news just popped up.  Apparently in Australia, Coca-Cola South Pacific ran advertising claiming that Coke was “kiddy-safe.”  The reason that they could do this was to take one of the ambiguous studies and state that there is no effect of SSBs on body weight, not that the study was inconclusive.  There could be flaws in the study cited so that statistical significance was not achieved.  However, the Australian Competition and Consumer Commission ordered that the advertising be corrected.  For the full story see here.

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a. There are many investigators that have graduated from UTSW, the University of “That Should Work”.  Just because something makes sense and we think it should work, doesn’t mean that it actually works that way.  For several examples in modern medicine see the ideology of health care.

b. Cause and effect will require a correlation, but a correlation does not mean cause and effect.  To ascertain a true cause and effect correlation must be established and two different types of experiments must be performed, adding the cause to observe the effect and removing the cause and losing the effect.

c.  So this study tested the correlation of cause removal and removal itself.  These are two of the three, criteria required for establishing cause and effect.  The role of SSB in casuing weight gain was not addressed in the study.

d. These findings have important implications for effectiveness of weight loss by dietary intervention.  If you want to loose weight quit drinking SSBs. These data also support decreasing the availability of SSBs in a public setting, such as schools.

1. http://www.ajcn.org/cgi/content/full/89/1/372

2. http://www.ajcn.org/cgi/content/full/89/1/438

3. http://www.ncbi.nlm.nih.gov/pubmed/18541554

4. http://www.ajcn.org/cgi/content/full/85/3/651

5. http://dx.doi.org/10.3945/ajcn.2008.27240

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Written by ecable

April 6, 2009 at 5:00 am

Posted in Health

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