Friday, January 20, 2012

Does Diet Pop Make You Fat?

Does diet pop make you fat? Is diet soda just as bad as regular soda?

I am often distressed when my patients with diabetes are drinking regular pop because they believe that diet pop is just as bad!

Where did people get this idea?

The idea that diet pop may make you fat may have come from a study that looked at diet pop use in 1550 adults in San Antonio. They found that those who consumed diet soda at the beginning of the study were more likely to have gained weight or have increased their waist circumference over the course of 7-9 years follow-up.

Like all epidemiological  studies, this study shows only an association. It proves nothing. It does not prove cause and effect. Epidemiological  studies deal with health in large groups or populations of people.

As one of the researchers admitted at the American Diabetes Association meeting last year, the results could be affected by a number of other factors not measured. These other factors are called confounding factors.

Let me give you an example of a hypothetical study with a confounding factor. A researcher wants to see if coffee use is associated with the future development of lung cancer. So he determines the use coffee consumption in a large group of people and follows them over 10 years. At the end of the 10 years, he finds that there is much more coffee use in those who get lung cancer as compared to those who do not get lung cancer.
He is ready to send this to the TV so the anchorwoman can scare millions of viewers.
Viewers will think that if they drink coffee they will be more likely to get lung cancer.

But wait! His researcher friend, a smarter dude, points out that  he failed to consider that the heavy coffee drinkers were more likely to  smoke cigarettes. The tobacco use was the likely explanation for the lung cancer.
In this case, the tobacco use was the confounding factor.

Another example of confounding  can be found in the Wikipedia entry  on this subject. This entry describes an association between drowning and eating ice cream. There are more drowning deaths when there is more ice cream consumption. But eating ice cream is not a likely cause of drowning. The confounding factor here is that both ice cream consumption and drowning are more frequent in hot weather.

So what might be confounding factors in the study looking at diet pop use?
Well, those who were having the greatest trouble controlling their weight might select artificially sweetened beverages over sugar sweetened ones.
It might just be that those people who were tending to get fat, chose diet pop.

Or maybe even more important, some people who drink diet soda think, that it's okay to eat high fat foods or candy. After all they save on calories by drinking the diet pop.
So it would not be the diet pop causing the weight gain, it would be the person’s food choices.

So those are two possible confounding factors.

And in this San Antonio study, the researchers saw the least weight gain in those who drank regular soda only. The soda with the calories!
Now this finding is hard to make sense of  and it is contrary to other larger epidemiological studies. That finding alone should make any thinking person question the results of this study.

But an earlier study  also showed an association between all soft drink consumption, both diet and regular, and weight gain.
On the other hand, a  large study in over 90,000 nurses failed to show an association between the  consumption of diet beverages and future weight gain.

These studies in part point out how confusing and almost worthless these epidemiological studies are. They stimulate interest but do not prove anything.

How about more meaningful studies, like controlled clinical trials?

What do controlled trials show about the commonly used non-nutritive or so called "artificial" sweeteners, like aspartame (Nutrasweet or Equal) and  sucralose (Splenda)?
Do they affect appetite or food intake in carefully performed clinical trials?
Do they change the substances in our body makes that affect our satiety or hunger?

Sucralose is not absorbed into the blood stream. No effects have been seen with sucralose on blood sugars, appetite, gut peptides that regulate appetite, stomach emptying or blood glucose control in people with diabetes.

Aspartame has been even more extensively studied. It may be helpful in a weight loss program. Aspartame does not increase hunger or calorie intake in short term studies.
Aspartame does not affect children's behavior. And, by the way,  table sugar, which is called sucrose, does not either.
And aspartame appears safe in high doses.

And when it comes to weight control, drinking aspartame sweetened beverages is clearly better than regular pop.

Studies showing a correlation between sugar sweetened beverages, regular soda, and future diabetes and weight gain are numerous. Here are a few: in 200420072008and 2010

Although the exact role of sugar sweetened beverages in the obesity epidemic is controversial. Regular pop is very likely a contributor.

And in the United States regular pop is  sweetened with high fructose corn syrup which may have unique harmful effects . More on this in a future post.

In any case, a 12 ounce can of regular soda typically has  around 140-160 calories. These are calories almost no one needs, especially if you are overweight.

Other sugar sweetened beverages like flavored waters, "energy" drinks, fruit punches, all  should be avoided, whether they have vitamins added or not.

So, given all of the above, diet pop is clearly better than regular pop.
And there is no convincing evidence of harm from diet pop or other beverages which are sweetened with non-nutritive or so called artificial sweeteners.
The research continues.
If you're unsure, avoid both diet pop and the regular nasty stuff.

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