Do Sodas Cause Obesity?

Do Diet Sodas Make You Fat?

Written by Dr. Steve Chaney on . Posted in Food and Health, Issues

Should You Kick the Diet Soda Habit?

Author: Dr. Stephen Chaney

Do Sodas Cause Obesity?We are consuming ever increasing amounts of diet sodas to combat the obesity epidemic. In 1960 14% of the U.S. population was obese and 3.3% of us consumed diet sodas. By 2010 41% of the U.S. population was obese and 20% of us were consuming diet sodas. It’s pretty clear that diet sodas aren’t helping us solve the obesity epidemic, but are they actually part of the problem?

You’ve probably seen the headlines questioning whether diet sodas actually help you lose weight. In fact many of the headlines imply the diet sodas will cause you to gain weight. Two of the more sensational headlines I came across said “Think diet sodas help you lose weight? Not so, Purdue study finds”, and “Can diet sodas actually cause more weight gain than regular sodas?”

Let me start with the first headline. The Purdue publication referred to in the headline (Swithers, Trends in Endocrin. & Metab., 24: 431-441) wasn’t really a study, it was an opinion piece. That simply means that it was a review where the references were selected on the basis of the author’s opinion. That’s OK if you clearly label it as an opinion piece, which Dr. Swithers did.

Now for the second headline: There is no good evidence that diet sodas will cause you to gain more weight than regular sodas. However, a number of published studies suggest that consumption of diet sodas is associated with weight gain – sometimes just as much weight gain as consumption of the sugar sweetened sodas they replace.

Do Diet Sodas Make You Fat?

The evidence that Dr. Swithers (Trends in Endocrin. & Metab., 24: 431-441) cited was pretty impressive.

For example, the San Antonio Heart Study recorded consumption of diet sodas and regular sugar sweetened sodas in 3,862 adults (average age 44) and measured the increase in BMI (a measure of obesity) over the next 7-8 years. That study found:

  • Individuals consuming >21 diet sodas/week were almost 2-fold more likely to become overweight or obese than individuals consuming no sodas.
  • There was a clear dose response effect, with a 41% increased risk of becoming overweight or obese for each can or bottle of diet soda consumed/day.
  • The increase in weight associated with diet soda consumption was just as great for those who were at normal weight at the beginning of the study as it was for those who were obese at the beginning of the study.
  • In this study the increase in weight associated with soda consumption was greater for diet sodas than it was for regular sodas.

Another major study (Circulation, 116: 480-488, 2007) recorded diet and regular soda consumption in 6039 participants in the Framingham Heart Study (average age 53) and measured the increase in obesity (along with other parameters associated with metabolic syndrome or pre-diabetes) over the next 4 years. This study found:

  • Individuals consuming one or more sodas/day had a 48% increased risk of becoming obese compared to people with infrequent soda consumption.
  • In this study the weight increase associated with soda consumption was virtually the same for diet sodas and regular sodas.

Are These Studies True?

Diet SodaThese, and similar studies have been criticized because they are looking at associations, which do not prove cause-and-effect. For example, it’s not always clear whether the people in those studies gained weight because they were consuming diet sodas or consumed diet sodas because they were overweight.

That argument is less persuasive for the San Antonio Heart Study, because the weight gain associated with diet soda consumption was also seen with people who were at normal weight at the beginning of the study. Still there is a need for good double blind, placebo controlled intervention studies.

There have been very few intervention studies in which one group of subjects were told to drink only diet sodas and the other group only regular sodas. Unfortunately, in those studies the total caloric intake of the diet soda group was also restricted. So while the diet soda group did lose weight, it’s not clear whether that weight loss was due to the diet sodas or the overall caloric restriction of the diet.

You may have also seen the recent headlines from a study showing that people consuming diet sodas gained no more weight than people consuming water (Obesity, 22: 1415-1421, 2014). But once again, both groups were given detailed instructions on how to restrict total calories. Almost any diet will work if you have a dietitian looking over your shoulder and telling you how to restrict calories.

So what is the average consumer to think? On the one hand, dietitians and health professionals are telling you to drink diet sodas if you want to lose weight. On the other hand, you keep seeing these headlines saying the diet sodas may not help you lose weight or may even cause you to gain weight.

Of all the recent blogs and online articles on the topic, the only one I actually recommend reading is from WebMD (http://www.webmd.com/diet/features/diet-sodas-and-weight-gain-not-so-fast).

WebMD often adheres to the AMA line, but I found this to be a very balanced analysis of the science behind the question of whether diet sodas help or hinder weight loss.

How Could Diet Sodas Possibly Cause Weight Gain?

The million dollar question is: How could diet sodas possibly cause weight gain? After all, they contain no calories. I think the most useful perspective from the Web MD article is that it’s probably not the diet sodas themselves that cause weight gain. It’s what we eat with the diet sodas that cause the weight gain. Here are a couple of quotes I found particularly enlightening.

Dr. Barry Popkin, a colleague from the University of North Carolina, calls it the “Big Mac and Diet Coke” mentality. He says: “Especially in America, we have a lot of people who eat high-fat, high-sugar diets, but also drink diet sodas.”

Why is that? Dr. David Katz from Yale University has research suggesting that artificial sweeteners may condition people to want to eat more sweet foods. He says: “Our taste buds don’t really differentiate between sweet in sugar and sweet from, say, aspartame. The evidence that this sweet taste is addictive is pretty clear. What I have seen in my patients is that those who drink diet soda are more vulnerable to processed foods with added sugars.”

There is some independent evidence to back up that hypothesis. For example, one recent study showed that rats given artificially sweetened yoghurt with their rat chow ate more rat chow and gained more weight than rats fed sugar-sweetened yoghurt with their rat chow (Behavioral Neuroscience, 122: 161-173, 2008). Another study in humans showed that consumption of artificial sweeteners activates a portion of the brain associated with cravings for sweets (Physiology & Behavior, 107: 560-567, 2012).

However, this viewpoint is controversial. Some experts think that the association between diet sodas and weight gain is psychological rather than physiological. Simply put, when people consume diet drinks they feel that they can splurge elsewhere.

The Bottom Line

  • Once again there is no magic bullet. There is no good evidence that diet sodas will help you lose weight unless you carefully control the calories in everything else you eat. And, diet sodas may just cause you to gain weight because they make you crave the very foods that are worst for your waistline.
  • In addition, there may be other good reasons not to consume diet sodas. For example, recent studies have shown that consumption of diet sodas may be linked to increased risk of metabolic syndrome or pre-diabetes (Circulation, 116: 480-488, 2007) and heart disease (see Does Sugar Cause Heart Disease? and Can Soft Drinks Cause Heart Disease?
  • My recommendations are to drink water, herbal teas, unsweetened tea & coffee or unsweetened mineral water or seltzer – perhaps with a splash of fruit juice.
  • Finally, there is no substitute for a healthy, calorie controlled diet; exercise; and lifestyle change if you want to lose weight and keep it off.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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Comments (1)

  • Mike Lucas

    |

    Great info Dr. Chaney! Thank you for the insight! Much appreciated!

    Mike & Jenn
    Shaklee Distributors
    Superior, WI

    Reply

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Latest Article

Should You Avoid Sugar Completely?

Posted October 24, 2017 by Dr. Steve Chaney

Is It The Sugar, Or Is It The Food?

Author: Dr. Stephen Chaney

 

Should we avoid sugar completely?  Almost every expert agrees that Americans should cut down on the amount of sugar we are consuming. However, for some people this has become a “sugar phobia”. They have sworn that “sugar shall never touch their lips”. Not only do they avoid sugar sweetened sodas and junk food, but they also have become avid label readers. They scour the label of every food they see and reject foods they find any form of sugar listed as an ingredient. Is this degree of sugar avoidance justified?

 

Should We Avoid Sugar to Keep it From Killing Us?

 

Let me add some perspective:

  • If you just take studies about the dangers of sugar at face value, sugar does, indeed, look dangerous. Excess sugar consumption is associated with increased risk of obesity, diabetes, and heart disease. However, when you look a little closer, you find that most of these studies have been done by looking at the correlation of each of these conditions with sugar sweetened beverage consumption (sodas and fruit juices).

A few studies have looked at the correlation of obesity and disease with total “added sugar” consumption. However, 71.6% of added sugar in the American diet comes from sugar sweetened beverages and junk food. None of the studies have looked at the sugar from healthy foods like fruits, vegetables, and whole grains. That’s because there is ample evidence that these foods decrease the risk of obesity, diabetes, and heart disease.

  • For example, if apples had a nutrition label, it would list 16 grams of sugar in a medium 80 calorie apple, which corresponds to about 80% of the calories in that apple. The sugar in an apple is about the same proportion of fructose and glucose found in high fructose corn syrup. Apples are not unique. The nutrition label would read about the same on most other fruits. Does that mean you should avoid sugar from all fruits? I think not.

Avoid Sugar or Avoid Certain Foods

 

avoid sugar from junk foodsThe obvious question is: “Why are the same sugars, in about the same amounts, unhealthy in sodas and healthy in fruits?” Let’s go back to those studies I just mentioned—the ones that are often used to vilify sugars. They are all association studies, the association of sugar intake with obesity and various diseases.

The weakness of association studies is the association could be with something else that is tightly correlated with the variable (sugar intake) that you are measuring. Could it be the food that is the problem, not the sugar?

If we look at healthy foods (fruits, vegetables, whole grains) they are chock full of vitamins, minerals, phytonutrients, fiber, and (sometimes) protein. Fiber and protein slow the absorption of sugar into the bloodstream. As a result, blood sugar levels rise slowly and are sustained at relatively low levels for a substantial period of time.

In sodas there is nothing to slow the absorption of blood sugar. You get rapid rise in blood sugar followed by an equally rapid fall. The same is true of junk foods consisting primarily of sugar, refined flour and/or fat.  Avoid sugar from those types of foods.

Another consideration is something called caloric density. Here is a simple analogy. I used to explain the concept of caloric density to medical students in my teaching days. There are about the same number of calories in a 2-ounce candy bar and a pound of apples (around 278 in the 2-ounce candy bar and 237 in a pound of apples). You can eat a 2-ounce candy bar and still be hungry. If you eat a pound of apples you are done for a while. In this example, the 2-ounce candy bar had a high caloric density (a lot of calories in a small package). Perhaps a more familiar terminology would be the candy bar was just empty calories.

Are Sodas and Junk Foods Killing Us?

avoid sugar from candyPutting all that together, you can start to understand why the foods the sugars are in are more important than the sugars themselves. When you consume sugars in the form of sugar sweetened beverages or sugary junk foods, your appetite increases. We don’t know for sure whether it is the intense sweetness of those foods, the rapid increase and fall in blood sugar, or the high caloric density (lots of calories ina small package) that makes us hungrier. It doesn’t matter. We crave more food, and it isn’t usually fruits, vegetables, and complex carbohydrates we crave. It’s more junk. That sets in motion a predictable sequence of events.

  • We overeat. Those excess calories are stored as fat and we become obese. [Note: The low carb enthusiasts will tell you our fat stores come from carbohydrates alone. That is incorrect. All excess calories, whether from protein, fat, or carbohydrate, are stored as fat.]
  • It’s not just the fat you can see (belly fat) that is the problem. Some of that fat builds up in our liver and muscles. This sets up an unfortunate sequence of metabolic events.
  • The fat stores release inflammatory cytokines into our bloodstream. That causes inflammation. Inflammation increases the risk of many diseases including heart disease and cancer.
  • The fat stores also cause our cells to become resistant to insulin. That reduces the ability of our cells to take up glucose, which leads to hyperglycemia and type 2 diabetes. [Note: The low carb enthusiasts will tell you carbohydrates cause type 2 diabetes. That is also incorrect. It is our fat stores that cause insulin resistance and type 2 diabetes. Our fat stores come from all excess calories, not just excess calories from carbohydrates.]
  • Insulin resistance also causes the liver to overproduce cholesterol and triglycerides and pump them into the bloodstream. That increases the risk of heart disease.
  • Sugar sweetened beverages and sugary junk foods also displace healthier foods from our diet. That leads to potential nutrient shortfalls that can increase our risk of many diseases.

However, none of this has to happen. The one thing that every successful diet has in common is the elimination of sodas, junk foods, fast foods and convenience foods. You should avoid sugar from those foods as much as possible. Once you eliminate those from your diet,you significantly enhance your chances of being at a healthy weight and being healthy long term.

 

What About Protein Supplements And Similar Foods?

Of course, the dilemma is what you, as an intrepid label reader, should do about protein supplements, meal replacement bars, or snack bars. They are supposed to be healthy, but the label lists one or more sugars. Even worse, the sugar content is higher than your favorite health guru recommends.  So, should you avoid sugar from supplements and the like?

In this case, a more useful concept is glycemic index, which is a measure of the effect of the food on your blood sugar levels. Healthy foods like apples may have a high sugar content, but they havea low glycemic index.

avoid sugar and consume protein to slow absorbptionThe same is true for the protein supplements and bars you are considering. Rather than looking at the sugar content, you should be looking for the term “low glycemic” on the label. That means there is enough fiber and protein in the food to slow the absorption of sugar into the bloodstream and stabilize your blood sugar levels.

What Does This Mean For You?

Don’t misunderstand me. I am not advocating for unlimited consumption of sugar. We should work on ways to avoid sugar or reduce the amount of sugar in our diet. On the other hand, we don’t need to become so strict that we and our family need to eat foods that taste like cardboard. We also don’t want to replace natural sugars with artificial sweeteners. I have warned about the dangers of artificial sweeteners previously.

We can go a long way towards reducing sugar by just eliminating sodas, other sugar sweetened beverages, junk foods, fast foods, convenience foods, and pastries from our diet. When considering fast foods and convenience foods, we should check the label for hidden sugar. For example, some Starbucks drinks are mostly sugar. When considering foods that are supposed to be healthy, we should look for the term “low glycemic” on the label.

So we don’t have to avoid sugar completely, but we should reduce sugar from sugar sweetened beverages and junk food.

 

The Bottom Line

 

We need to keep warnings about the dangers of sugar in perspective:

  • The studies showing that sugar consumption leads to obesity, diabetes, and heart disease have all been done with sodas and junk foods.
  • Many fruits have just as much sugar as a soda. They also contain about the same proportion of fructose and glucose as high fructose corn syrup. Yet we know fruits are good for us.
  • Diets rich in fruits, vegetables and whole grains decrease our risk of obesity, diabetes, and heart disease.
  • That is because the sugar in whole foods is generally present along with fiber and protein, which slows the absorption of sugar and prevents the blood sugar spikes we get with sodas and junk foods.
  • In the case of prepared foods like protein supplements, you should look for “low glycemic” on the label rather than sugar content. Low glycemic means that there is enough fiber and protein in the product to slow the absorption of sugar and prevent blood sugar spikes.
  • Don’t misunderstand me. I am not advocating for unlimited consumption of sugar. We should all work on ways to avoid sugar from junk foods or to reduce the amount of sugar in our diet. On the other hand, we don’t need to become so strict that we and our family need to eat foods that taste like cardboard. We also don’t want to replace natural sugars with artificial sweeteners.
  • We can go a long way towards reducing sugar by just eliminating sodas, other sugar sweetened beverages, junk foods, fast foods, convenience foods, and pastries from our diet. When considering fast foods and convenience foods, we should check the label for hidden sugar. When considering foods that are supposed to be healthy, we should look for the term “low glycemic” on the label.

For more details, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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