Why Do Diet Sodas Make You Fat?

Is Mixing Diet Sodas With Carbs Bad For You?

Why Do Sodas Cause Obesity?Many people, and many doctors, believe that diet sodas and artificially sweetened foods are a healthy choice. After all:

  • Cutting calories by drinking diet sodas and eating artificially sweetened foods should help you lose weight.
  • If sugar is the problem for diabetics, diet sodas and artificially sweetened foods should be a healthier choice.

On the surface, these ideas appear to be self-evident. They seem to be “no-brainers”. The truth, however, is more complicated.

When studies are tightly controlled by dietitians so that the people consuming diet sodas don’t add any extra calories to their diet, the results are exactly as expected. People consuming diet sodas lose weight compared to people drinking regular sodas.

However, as I have described in an earlier issue of “Health Tips From the Professor”, the results are different in the real world where you don’t have a dietitian looking over your shoulder. In those studies, diet sodas are just as likely to cause weight gain as regular sodas.

As Barry Popkin, a colleague at the University of North Carolina, put it” “The problem is that we [Americans] are using diet sodas to wash down our Big Macs and fries.” In short, people drinking diet sodas tend to increase their caloric intake by adding other foods to their diet. Even worse, the added foods aren’t usually fruits and vegetables. They are highly processed junk foods.

Why is that? The short answer is that nobody knows (more about that later). However, a recent study (JR Dalenberg et al, Cell Metabolism, 31: 493-502, 2020) suggests an unexpected mechanism for the weight gain associated with diet soda consumption. Let’s look at that study.

How Was The Study Done?

Clinical StudyThe study recruited 45 healthy young adults (ages 20-45) who habitually consumed less than 3 diet sodas a month. They were randomly assigned to three groups. The participants in each group came into the testing facility seven times over a span of 2 weeks. Each time they were given 12 ounces of one of three equally sweet tasting beverages in a randomized, double-blind fashion.

  • Group 1 received a sucralose-sweetened drink contained 0.06 grams of sucralose (equivalent to two packets of Splenda).
  • Group 2 received a sugar-sweetened drink contained 7 teaspoons of sucrose (table sugar).
  • Group 3 received a combo drink contained 0.06 grams of sucralose plus 7 teaspoons of maltodextrin. Maltodextrin is a water-soluble carbohydrate that does not have a sweet taste.

o   Maltodextrin was used because Splenda and most other commercial sucralose products contain it along with sucralose. You need something to fill up those little sucralose-containing packets.

o   This drink was included as a control. The expectation was that it would give the same results as the sucralose-sweetened drink.

Three measurements were performed prior to and following the 2-week testing period:

  • An oral glucose tolerance test in which participants drink a beverage containing a fixed amount of glucose. Then their blood sugar and blood insulin levels are measured over the next two hours.

o   This is a measure of how well they were able to control their blood sugar levels.

  • A test in which they were given samples that had either a sweet, sour, salty, or savory taste. Then:

o   They were asked to identify each taste and report how strong the taste was.

o   MRI scans of their brains were performed to determine how strongly their brains responded to each of the tastes.

Is Mixing Diet Soda With Carbs Bad For You?

The results were surprising. The first surprise came when the investigators unblinded the results of the oral glucose tolerance test:

  • Blood sugar and blood insulin responses were unaffected by the 2-week exposure to sugar-sweetened drinks.

o   This was expected.

  • Blood sugar and blood insulin were relatively unaffected by the 2-week exposure to sucralose-sweetened drinks. If anything, the control of blood sugar levels was slightly improved at the end of two weeks.

o   This was a disappointment for the investigators. One of the prevailing theories is that artificially sweetened beverages alter the blood sugar response. The investigators found no evidence for that idea.

  • Following the 2-week exposure to the combo drinks (sucralose plus maltodextrin), blood sugar levels were unaffected, but blood insulin levels were increased. This implies that more insulin was required to control blood sugar levels. In other words, these participants had developed insulin resistance.

o   This result was unexpected. Remember the investigators had included this drink as a control.

o   The investigators pointed out that the insulin resistance associated with the sucralose-maltodextrin combo could increase the risk of type 2 diabetes and obesity.

  • Because of this unexpected result, the investigators did a follow-up study in which participants were given a maltodextrin-only drink using the same study protocol. The oral glucose tolerance test was unchanged by the 2-week exposure to maltodextrin-only drinks.

When the investigators conducted taste tests, the ability of participants to taste all four flavors was unchanged by a 2-week exposure to any of the drinks.

However, when the investigators did MRI scans to measure the brain’s response to these flavors:

  • A two-week exposure to the sucralose plus maltodextrin drinks reduced the brain’s response to sweet but not to any of the other flavors.

o   In other words, the subjects could still taste sweet flavors, but their brains were not responding to the sweet taste. Since sweetness activates pleasure centers in the brain this could lead to an increased appetite for sweet-tasting foods.

o   This might explain the weight gain that has been observed in many previous studies of diet sodas.

  • Two-week exposures to the other drinks had no effect on the brain’s response to any of the flavors. Once again, this effect was only seen in the sucralose-maltodextrin combination.

The investigators concluded:

  • “Consumption of sucralose combined with carbohydrates impairs insulin sensitivity…and…neural responses to sugar.
  • Insulin sensitivity is not altered by sucralose or carbohydrate consumption alone.
  • The results suggest that consumption of sucralose in the presence of a carbohydrate dysregulates gut-brain regulation of glucose metabolism.”

The investigators pointed out that this could have several adverse consequences. Again, in the words of the authors:

“Similar exposure combinations (artificial sweeteners plus carbohydrates) almost certainly occur in free-living humans, especially if one considers the consumption of a diet drink along with a meal. This raises the possibility that the combination effect may be a major contributor to the rise in incidence of type 2 diabetes and obesity. If so, addition of artificial sweeteners to increase the sweetness of carbohydrate-containing food and beverages should be discouraged and consumption of diet drinks with meals should be counseled against.”

Why Do Diet Sodas Make You Fat?

As I mentioned at the start of this article, there are a lot of hypotheses as to why diet sodas make us fat. These hypotheses break down into two classifications: psychological and physiological.

The psychological hypothesis is easiest to explain. Essentially, it goes like this: We feel virtuous for choosing a zero-calorie sweetener, so we allow ourselves to eat more of our favorite foods. It is unlikely that this hypothesis holds for all diet soda drinkers. However, it is also hard to exclude it as at least part of the explanation for the food overconsumption associated with diet soda use.

There are multiple physiological hypotheses. Most of them are complicated, but here are simplified explanations of the three most popular hypotheses:

  • The sweet taste of artificial sweeteners tricks the brain into triggering insulin release by the pancreas. This causes blood sugar levels to plummet, which increases appetite.
  • The sweet taste of artificial sweeteners is not appropriately recognized by the brain. This diminishes release of hormones that suppress appetite.
  • Artificial sweeteners interfere with insulin signaling pathways, which leads to insulin resistance.

There is some evidence for and against each of these hypotheses.

However, this study introduces a new physiological hypothesis – namely that it is the combination of artificial sweeteners and carbohydrates that results in a dysregulation of the normal mechanisms controlling appetite and blood sugar.

What Does This Study Mean For You?

Diet Soda DangersLet’s start with the obvious. This is just a hypothesis.

  • This was a very small study. Until it is confirmed by other, larger studies, we don’t know whether it is true.
  • This study only tested sucralose. We don’t know whether this applies to other artificial sweeteners.
  • The study only tested maltodextrin in combination with sucralose. We don’t know whether it applies to other carbohydrates.

Therefore, in discussing how this study applies to you, let’s consider two possibilities – if it is true, and if it is false.

If this hypothesis is true, it is concerning because:

  • We often consume diet sodas with meals. If, for example, we take the earlier example of a diet soda with a Big Mac and fries, both the hamburger bun and the fries are high carbohydrate foods.

 

  • Sucralose and other artificial sweeteners are used in low calorie versions of many carbohydrate rich processed foods.

If this hypothesis is false, it does not change the underlying association of diet soda consumption with weight gain and type 2 diabetes. It is merely an attempt to explain that association. We should still try to eliminate diet sodas and reduce our consumption of artificially sweetened, low calorie foods.

My recommendation is to substitute water and other unsweetened beverages for the diet drinks or sugar sweetened beverages you are currently consuming. If you crave the fizz of sodas, drink carbonated water. If you need more taste, try herbal teas or infuse water with slices of lemon, lime, or your favorite fruit. If you buy commercial brands of flavored water, check the labels carefully. They may contain sugars or artificial sweeteners. Those you want to avoid.

The Bottom Line

Many studies have called into question the assumption that diet sodas and diet foods help us lose weight. In fact, most of these studies show that diet soda consumption is associated with weight gain rather than weight loss.

There are many hypotheses to explain this association, but none of them have been proven at present.

This study introduces a new hypothesis – namely that the combination of artificial sweeteners and carbohydrates results in a dysregulation of the normal mechanisms controlling appetite and blood sugar. In particular, this study suggested that combining sucralose with carbohydrates caused insulin resistance and reduce the ability of the brain to respond appropriately to sweet tastes.

The authors concluded: “Similar exposure combinations (artificial sweeteners plus carbohydrates) almost certainly occur in free-living humans, especially if one considers the consumption of a diet drink along with a meal. This raises the possibility that the combination effect may be a major contributor to the rise in incidence of type 2 diabetes and obesity. If so, addition of artificial sweeteners to increase the sweetness of carbohydrate-containing food and beverages should be discouraged and consumption of diet drinks with meals should be counseled against.”

If this hypothesis is true, it is concerning because:

  • We often consume diet sodas with meals. If, for example, we take the example of a diet soda with a Big Mac and fries, both the hamburger bun and the fries are high carbohydrate foods.
  • Artificial sweeteners are used in low calorie versions of many carbohydrate rich processed foods.

If this hypothesis is false, it does not change the underlying association of diet soda consumption with weight gain and type 2 diabetes. It is merely an attempt to explain that association. We should still try to eliminate diet sodas and reduce our consumption of artificially sweetened, low calorie foods.

My recommendation is to substitute water and other unsweetened beverages for the diet drinks or sugar sweetened beverages you are currently consuming. If you crave the fizz of sodas, drink carbonated water. If you need more taste, try herbal teas or infuse water with slices of lemon, lime, or your favorite fruit. If you buy commercial brands of flavored water, check the labels carefully. They may contain sugars or artificial sweeteners. Those you want to avoid.

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.

How Much Carbohydrates Should We Eat?

The “Goldilocks Effect”

Author: Dr. Stephen Chaney

 

How much carbohydrates should we eat?

how much carbohydrates should we eatThe low-carb wars rage on. Low-carb enthusiasts claim that low-carb diets are healthy. Many health experts warn about the dangers of low-carb diets. Several studies have reported that low-carb diets increase risk of mortality (shorten lifespan).

However, two recent studies have come to the opposite conclusion. Those studies reported that high carbohydrate intake increased mortality, and low carbohydrate intake was associated with the lowest mortality.

One of those studies, called the Prospective Urban Rural Epidemiology (PURE) study was published just last year. It included data from 135,335 participants from 18 countries across 5 continents. That’s a very large study, and normally we expect very large studies to be accurate. The results from the PURE study had low-carb enthusiasts doing a victory lap and claiming it was time to rewrite nutritional guidelines to favor low-carb diets.

Whenever controversies like this arise, reputable scientists are motivated to take another look at the question. They understand that all studies have their weaknesses and biases. So, they look at previous studies very carefully and try to design a study that eliminates the weaknesses and biases of those studies. Their goal is to design a stronger study that reconciles the differences between the previous studies.

how much carbohydrates should we eat studySuch a study has just been published (SB Seidelmann et al, The Lancet, doi.org/10.1016/S2468-2667(18)30135-X ). This study resolves the conflicting data and finally answers the question: “How much carbohydrates should we be eating if we desire a long and healthy life?” The answer is “Enough.”

I call this “The Goldilocks Effect” You may remember “Goldilocks And The Three Bears.” One bed was too hard. One bed was too soft. But, one bed was “just right.” One bowl of porridge was too hot. One was two cold. But, one was “just right.”  According to this study, the same is true for carbohydrate intake. High carbohydrate intake is unhealthy. Low carbohydrate intake is unhealthy. But, moderate carbohydrate intake is “just right.”

How Was The Study Done?

This study was performed in two parts. This first part drew on data from the Atherosclerosis Risk in Communities (ARIC) study. That study enrolled 15,428 men and women, aged 45-64, from four US communities between 1987 and 1989. This group was followed for an average of 25 years, during which time 6283 people died. Carbohydrate intake was calculated based on food frequency questionnaires administered when participants enrolled in the study and again 6 years later. The study evaluated the association between carbohydrate intake and mortality.

The second part was a meta-analysis that combined the data from the ARIC study with all major clinical studies since 2007 that measured carbohydrate intake and mortality and lasted 5 years or more. The total number of participants included in this meta-analysis was 432,179, and it included data from both studies that claimed low-carbohydrate intake was associated with decreased mortality.

 

How Much Carbohydrates Should We Eat?

 

how much carbohydrates should we eat ripThe results from the ARIC study were:

  • The relationship between mortality and carbohydrate intake was a U-shaped curve.
  • The lowest risk of death was observed with a moderate carbohydrate intake (50-55%). This is the intake recommended by current nutrition guidelines.
  • The highest risk of death was observed with a low carbohydrate intake (<40%).
  • The risk of death also increased with very high carbohydrate intake (>70%).
  • When the investigators used the mortality data to estimate life expectancy, they predicted a 50-year old participant would have a projected life expectancy of:
  • 1 years if they had a moderate intake of carbohydrates.
  • Their life expectancy was 4 years less if they had a low carbohydrate intake.
  • Their life expectancy was 1.1 year less if they had a very high carbohydrate intake.
  • The risk associated with low carbohydrate intake was affected by what the carbohydrate was replaced with.
  • When carbohydrate was replaced with animal protein and animal fat there was an increased risk of mortality on a low-carb diet. The animal-based low-carb diet contained more beef, pork, lamb, chicken and fish. It was also higher in saturated fat.
  • how much carbohydrates should we eat plantbasedWhen carbohydrate was replaced with plant protein and plant fats, there was a decreased risk of mortality on a low-carb diet. The plant-based low-carb diet contained more nuts, peanut butter, dark or whole grain breads, chocolate, and white bread. It was also higher in polyunsaturated fats.
  • The effect of carbohydrate intake on mortality was virtually the same for all-cause mortality, cardiovascular mortality, and non-cardiovascular mortality.
  • There was no significant affect of carbohydrate intake on long-term weight gain (another myth busted).

The results from the meta-analysis were very similar. When the data from all studies were combined:

  • Both low carbohydrate diets and very high carbohydrate diets were associated with increased mortality.
  • Meat-based low-carb diets increased mortality, and plant-based low-carb diets decreased mortality.
  • Once again, the results were the same for total mortality, cardiovascular mortality, and non-cardiovascular mortality.

The authors concluded: “Our findings suggest a negative long-term association between life-expectancy on both low carbohydrate and high carbohydrate diets…These data also provide further evidence that animal-based low carbohydrate diets should be discouraged. Alternatively, when restricting carbohydrate intake, replacement of carbohydrates with predominantly plant-based fats and proteins could be considered as a long-term approach to healthy aging.”

Why Were Some Previous Studies Misleading?

This study also resolved the discrepancies between previous studies. The authors pointed out that the average carbohydrate intake is very different in Europe and the US than in Asian countries and low-income countries. In the US and Europe, mean carbohydrate intake is about 50% of calories and it ranges from 25% to 70% of calories. With that range of carbohydrate intake, it is possible to observe the increase in mortality associated with both low and high carbohydrate intakes.

White rice is a staple in Asian countries, and protein is a garnish rather than a main course. Consequently, overall carbohydrate intake is greater in Asian countries and very few Asians eat a low carbohydrate diet. High protein foods tend to be more expensive than high carbohydrate foods. Thus, very few people in developing countries can afford to follow a low carbohydrate diet, and overall carbohydrate intake also tends to be higher.

how much carbohydrates should we eat aricTherefore, in Asian and developing countries the average carbohydrate intake is greater (~61%) than in the US and Europe, and the range of carbohydrate intake is from 45% to 80% of calories. With that range of intake, it is only possible to see the increase in mortality associated with high carbohydrate intake.

Both the studies that low-carb enthusiast quote to support their claim that low-carb diets are healthy relied heavily on data from Asian and developing countries. In fact, when the authors of the current study overlaid the data from the PURE study with their ARIC data, there was an almost perfect fit. The only difference was that their ARIC data covered both low and high carbohydrate intake while the PURE study touted by low-carb enthusiasts only covered moderate to high carbohydrate intake. [I have given you my rendition of the graph on the left. If you would like to see the data yourself, look at the paper .]

Basically, low-carb advocates are telling you that diets with carbohydrate intakes of 30% or less are healthy based on studies that did not include carbohydrate intakes below 40%. That is misleading. The studies they quote are incapable of detecting the risks of low carbohydrate diets.

What Does This Mean For You?

There are several important take-home lessons from this study:

  • All major studies agree that very high carbohydrate intake is unhealthy. In part, that reflects the fact that diets with high carbohydrate intake are likely to be high in sodas and sugary junk foods. It may also reflect the fact that diets which are high in carbohydrate are inevitably low in protein or healthy fats or both.
  • how much carbohydrates should we eat low-carbAll studies that cover the full range of carbohydrate intake agree that low carbohydrate intake is also unhealthy. It shortens life expectancy of a 50-year old by about 4 years.
  • The studies quoted by low carb enthusiasts to support their claim that low-carb diets are healthy don’t include carbohydrate intakes below 40%. That means their claims are misleading. The studies they quote are incapable of detecting the risks of low carbohydrate diets.
  • Meat-based low-carb diets decrease life expectancy while plant-based low carb diets increase life expectancy. This is consistent with previous studies. For more details on those studies, see my article “Are Any Low-Carb Diets Healthy?” in “Health Tips From The Professor” or my book, “Slaying The Food Myths.”

The health risks of meat-based low-carb diets may be due to the saturated fat content or the heavy reliance on red meat. However, the risks are just as likely to be due to the foods these diets leave out – typically fruits, whole grains, legumes, and some vegetables. Proponents of low-carb diets assume that you can make up for the missing nutrients by just taking a multivitamin. However, each food group also provides a unique combination of phytonutrients and fibers. The fibers, in turn, influence your microbiome. Simply put, whenever you leave out whole food groups, you put your health at risk.

Limitations Of This Study

how much carbohydrates should we eat limitationsMy main concern with this study and all previous studies is that they lump all carbohydrates together, as if they were equally healthy or unhealthy. We should really be focusing on healthy carbohydrates versus unhealthy carbohydrates, healthy proteins versus unhealthy proteins, and healthy fats versus unhealthy fats. We should be focusing on foods.

For example, the plant-based low carbohydrate diets in this study probably had a higher percentage of healthy carbohydrates because those diets feature whole, plant-based foods. The very high carbohydrate diets in this study probably had a higher percentage of unhealthy carbohydrates. However, we have no idea whether the diets with moderate carbohydrate intake featured healthy carbohydrates or unhealthy carbohydrates. That is critical because moderate carbohydrate intake was the baseline to which all other diets were compared.

An important unanswered question is: “What is the relationship between carbohydrate intake and lifespan when most of the carbohydrates come from whole, plant-based foods?” Is low carbohydrate intake healthier or less healthy than moderate carbohydrate intake? Is high carbohydrate intake still less healthy? We have no idea. No studies have analyzed the data in that way.

Similarly, we know from multiple studies that meat-based, low-carb diets increase mortality and plant-based, low-carb diets decrease mortality when compared to moderate carbohydrate intake with no differentiation of protein source. But, what if the moderate carbohydrate group had also been subdivided into meat eaters and plant eaters? Would meat-based, low-carb diets still be less healthy than meat-based, moderate-carbohydrate diets? Would plant-based,  low-carb diets still be healthier than plant-based, moderate-carb diets? We have no idea.

 

The Bottom Line

The low-carb wars are raging. Several studies have reported that low-carb diets increase risk of mortality (shorten lifespan). However, two recent studies have come to the opposite conclusion. Those studies have low-carb enthusiasts doing a victory lap and claiming it is time to rewrite nutritional guidelines to favor low-carb diets.

However, a study just published a couple of weeks ago resolves the conflicting data and finally answers the question: “How much carbohydrate should we be eating if we desire a long and healthy life?” The answer is “Enough.”

I call this “The Goldilocks Effect.”  According to this study, high carbohydrate intake is unhealthy. Low carbohydrate intake is unhealthy. But, moderate carbohydrate intake is “just right.”

Specifically, this study reported:

  • Moderate carbohydrate intake (50-55%) is healthiest. This is also the carbohydrate intake recommended by current nutritional guidelines.
  • All major studies agree that very high carbohydrate intake (60-70%) is unhealthy. It shortens life expectancy of a 50-year old by about a year.
  • All studies that cover the full range of carbohydrate intake agree that low carbohydrate intake (<40%) is also unhealthy. It shortens life expectancy of a 50-year old by about 4 years.
  • The studies quoted by low carb enthusiasts to support their claim that low-carb diets are healthy don’t include carbohydrate intakes below 40%. That means their claims are misleading. The studies they quote are incapable of detecting the risks of low carbohydrate diets.
  • Meat-based, low-carb diets decrease life expectancy while plant-based, low carb diets increase life expectancy. This is consistent with the results of previous studies.

The authors concluded: “Our findings suggest a negative long-term association between life-expectancy and both low carbohydrate and high carbohydrate diets…These data also provide further evidence that animal-based low carbohydrate diets should be discouraged. Alternatively, when restricting carbohydrate intake, replacement of carbohydrates with predominantly plant-based fats and proteins could be considered as a long-term approach to healthy aging.”

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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