Why Does Processed Food Make You Fat?

January 23, 2024 by Dr. Steve Chaney

How Can You Enjoy Eating Without Getting Fat?

Author: Dr. Stephen Chaney

You are probably tired of hearing about how bad processed foods are for you. If you have been following the headlines, you probably already know that diets high in processed foods are linked to obesity, type 2 diabetes, heart disease, some forms of cancer, memory loss, liver disease, kidney disease, depression, risk of dying from any cause, and much more.

And this is a serious problem because 60-70% of the American diet comes from processed foods.

In fact, you may have seen these headlines so frequently that your eyes glaze over, and your mind shuts down any time you see the words “processed foods” in the title.

This week I will be sharing the latest studies on why processed foods make us fat. Stick with me on this. This is not just another article on processed foods. While the focus of the article is on processed foods, the studies it covers are valuable because they also identify some unprocessed foods that can make us fat.

Spoiler alert! Today’s “Health Tip” is important because it teaches us that weight control is not as simple as eliminating processed foods from our diet. We also need to know which unprocessed or minimally processed foods to eat less of.

Before I proceed, I should give you a brief review of how processed foods are defined because that definition has changed in recent years.

What Are Processed Foods?

Everyone used to have a good understanding of which foods were processed. But several years ago, the scientific community introduced a new food classification system called “The NOVA food classification system” and introduced a new category – ultra-processed foods. I have covered this classification system in previous “Health Tips From the Professor” articles, but I will review it here.

The NOVA system categorizes foods into four groups according to the extent of processing they have undergone:

Unprocessed foods.

- This category includes foods like fruit, vegetables, milk, eggs, and meat.

2) Processed culinary ingredients.

- This category includes foods you might find in restaurants or prepare yourself to which things like salt, sugar, vegetable oils, butter, or cream were added in the preparation.

3) Minimally processed foods.

- This category includes foods like canned vegetables, freshly made breads, and cheeses.

4) Ultra-processed foods.

- This category includes foods like soft drinks, chips, packaged snacks, most breakfast cereals, chicken nuggets & fish sticks, fast food burgers, hot dogs, and other processed meats.

The actual list is much longer, but you get the idea. What we call processed foods, scientists now call ultra-processed foods. The article I am discussing used the term “ultra-processed foods” in the title.

But, since the term “ultra-processed foods” has not yet entered the popular vocabulary, I will use the term “processed foods” in this article because it is more understandable to the average reader.

Does Processed Food Make You Fat?

I shared a study in a previous issue of “Health Tips From the Professor” that suggested that the answer was yes, but did not answer the question of why. That’s because of the way the experiment was designed.

The ultra-processed diet and unprocessed diets were matched with respect to:

Total calories in the food portions given to the subjects.

Caloric density (calories per serving size). That’s because caloric density has been linked to overeating (I’ll discuss that in more detail below.) The authors of the study eliminated that variable.

Macronutrients (carbohydrate, fat, & protein). I’m sure you’ve seen blogs suggesting that carbohydrates or fat cause weight gain. And you’ve probably seen blogs suggesting that high protein diets cause weight loss. The authors eliminated these variables.

Total sugar, fiber, and sodium. That’s because the sugar, fat, and sodium content of foods increase their tastiness (palatability), which has been linked to overeating (more below). The authors eliminated this variable.

In short, this study compared a tasty, healthy ultra-processed food diet with a tasty, healthy unprocessed food diet. [Note: This does not represent the real world. In the real world the ultra-processed foods eaten by most Americans are higher in caloric density, sugar, fat, and sodium and lower in fiber than unprocessed foods.]

However, in the scientific world, this was an excellent study design. By eliminating variables thought to explain the correlation between ultra-processed food consumption and obesity, the study was able to focus on two questions:

#1: With those variables eliminated, do ultra-processed foods still lead to overeating? Here the answer was a clear, yes.

The study participants eating ultra-processed foods ate 500 more calories per day than those eating unprocessed foods. (Both groups were presented with meals and snacks containing the same number of calories and told to eat as much as they wanted.)

Participants eating ultra-processed foods gained 2 pounds in just two weeks, while those eating unprocessed foods lost 2 pounds.

#2: If so, what else about ultra-processed foods leads to overeating? One popular theory of why ultra-processed foods lead to overeating is that they cause large blood sugar spikes and crashes, which stimulates appetite. But the authors of the study were disappointed to find no large blood sugar spikes following consumption of ultra-processed food meals.

However, I don’t think their data disproves the blood sugar spike theory. Remember that this was a “healthy ultra-processed food diet”. The amount of sugar and fiber was identical in the ultra-processed and unprocessed food diets. More importantly, when I looked at the sample menus provided by authors as supplementary information, each meal contained a significant percent of whole, low-glycemic foods. This was a “healthy ultra-processed food” diet designed by a dietitian, not what the typical American eats.

So, why did the ultra-processed food group eat more in this study? This study did not provide an answer to that question, but other studies (described below) have provided probable answers to that question.

Why Does Processed Food Make You Fat?

What do other studies tell us about why processed foods make us overeat and gain weight? Here are the top 7 mechanisms that have been suggested and what they mean for us.

#1: Caloric Density: Simply put, caloric density is the number of calories in a serving of food. When you consume foods with a high caloric density, you are more likely to consume excess calories without even thinking about it.

When I was still teaching medical students, I used this example to illustrate the effect of caloric density on calories consumed. “There are the same number of calories in a 2-ounce candy bar and a pound of apples. You can eat a 2-ounce candy bar and be ready to eat more. If you eat a pound of apples, you are done for a while”.

Since most processed foods have a higher caloric density than unprocessed foods, the simplest solution to weight control is to limit processed foods in your diet.

However, how you or your favorite restaurant prepares unprocessed foods is important as well. For example, the addition of cheese or cream sauces can significantly increase the caloric density of the food. This is why the NOVA food classification system I described above created a new category of “culinary foods” to describe these kinds of foods.

#2: Hyper-palatability: In prehistoric times foods that were sweet, salty, and fatty were essential for survival, so we are hardwired to desire those foods. Here is why:

We need a certain amount of sugar for our brain, red blood cells, and a few other tissues to function. Wild game provides almost no carbohydrate. Fruits were the best source of sugar, but fruits were scarce prior to farming. The craving for sweetness drove us to forage far and wide to find fruits and other plant sources of sugar and carbohydrate.

Sodium is essential for survival, but unprocessed plant and animal foods provide very little. That’s why even in Biblical times, salt was worth its weight in gold.

In prehistoric times, food was sometimes scarce, especially in winter. It might be a week or more between meals. Fat stores got prehistoric man through these times of scarcity, so it was important to eat fatty meals in times of plenty. [Note: We no longer live in times of scarcity, and those fat stores have gone from being an asset to being a health concern.]

Unfortunately, “Big Food, Inc” has weaponized these hardwired desires for sweet, salty, and fatty foods. Simply put, processed foods taste good because they fulfil our hardwired taste desires. Scientists call it “hyper-palatability”. But whatever you call it, we want to eat more, and that leads to overeating.

And again, the way we prepare the foods we eat also matters. It’s only natural to add extra salt, sugar, and/or fat to the foods we prepare so they taste better. And if we add too much, we make the healthy foods we eat hyper-palatable, and we are tempted to overeat.

On a personal note, I never knew you might want to add sugar and fat to the vegetables you cook before my family moved to the south. On the other hand, I had never eaten collard greens before either.

#3: Food Consistency: When you look at studies on the effect of food consistency on calories consumed, you find that there are several different ways of defining food consistency, but they are all looking at the same thing from a different perspective – like the fable of the 6 blind men trying to describe an elephant.

Food Structure: The classic study, published in 2009, compared the effect of sliced apples, applesauce, and apple juice eaten shortly before a meal on the number of calories consumed at the meal. In terms of calories consumed during the meal, the results were clear. It was apple juice > applesauce > apple slices.

This drew attention to the effect of food structure on calories consumed. Apples are a whole food with cellular structure intact. Applesauce contains all the nutrients, phytonutrients, and fiber of whole apples, but the cellular structure has been lost. Apple juice contains most of the nutrients and phytonutrients of applesauce, but the fiber has been lost.

Why does the structure of whole foods matter?

- Cell structure must be destroyed before digestion can occur, the release of sugar and carbohydrates from the food is delayed. This reduces the spikes and valleys of blood sugar that can increase appetite.

- Transit time of the food through the intestine is also delayed. Thus, the feeling of fulness persists longer, which reduces appetite.

There are two takeaway lessons from this study that may not be so obvious:

- Neither applesauce nor apple juice meet the NOVA definition of an ultra-processed food. So, simply removing processed foods from your diet may not be enough to reduce your appetite and, therefore, your caloric intake.

- In addition, adding fiber back to apple juice did not make it equivalent to applesauce in reducing appetite. So, despite what Big Food Inc tells you, adding fiber to processed foods does not turn them into health foods.

Soft Versus Hard Foods: Many processed foods are soft, and most unprocessed foods are hard. So, you could think of this as a description that separates processed foods from unprocessed foods.

But, if you consider the apples versus applesauce comparison I described above, it is obvious that soft versus hard description also pertains to minimally processed foods such as applesauce and whole, unprocessed foods such as apples.

For example, one recent study comparing soft versus hard foods found it didn’t matter whether the soft foods were processed or unprocessed. People in the study ate more calories from all soft foods than from hard, unprocessed foods such as raw fruits and vegetables.

Fast Versus Slow Foods: This description separates foods based on the speed at which they are digested and pass through the intestine. Once again, you might think of this as a description that separates processed and unprocessed foods until you think about applesauce versus apples comparison.

And, as you might expect, a recent study comparing “fast” versus “slow” foods found it didn’t matter whether the fast and slow foods were processed or unprocessed. People in the study ate more calories from fast foods than from slow foods.

[Note: This study defined “slow” foods as harder, chunkier, more solid, and more viscous. While the first three adjectives describe what other scientists also refer to as “hard” foods, the final adjective broadens the category to include “soft” foods like oatmeal.]

How Can You Enjoy Eating Without Getting Fat?

For most Americans, weight is a constant uphill battle. Their weight increases by a few pounds every year, and over time that continuing weight gain adds up. Diets are never enjoyable, which is part of the reason they almost always fail in the long term. You want to control your weight, but you also want to enjoy what you eat. Why is that so hard?

The secret to a healthy weight is to find foods you enjoy that don’t increase your appetite – foods that fill you up, so you eat less naturally. Here are my 4 tips for eating foods you enjoy without getting fat.

Tip #1: Limit processed foods. Processed foods tend to have a high caloric density; are hyper-palatable, soft, and fast; and lack the intact cellular structure of whole, unprocessed foods. And multiple studies, such as the one I cited above, agree that processed foods cause us to eat more and to gain weight. So, the single most important step you can take to control your weight is to limit your intake of processed foods.

Tip #2: Choose minimally processed foods wisely. The studies I shared above suggest that avoiding processed foods may not be enough. We also need to look at the minimally processed foods we eat (applesauce, for example). These studies suggest we should also favor whole, unprocessed foods over minimally processed foods that are softer and faster (more quickly digested).

By now, you might be saying, “Wait a minute. I thought you said I could enjoy eating without getting fat. How can I enjoy eating if I have to give up my favorite processed and minimally processed foods?”

My short answer would be, “No. But you might want to broaden your horizons”. We all tend to be creatures of habit. We eat a relatively small variety of foods on a regular basis. When my wife and I decided to eat healthier, we kept trying new foods until we found new, healthier foods we loved.

The category of whole unprocessed foods offers many options. There are fruits, vegetables, many varieties of 100% whole grains, beans, nus, seeds, eggs, and meats. And we are blessed to live in a country with abundant choices. When you walk into your local supermarket you will find dozens of foods in each of these categories that you have never tried before. Be daring. Keep trying new foods until you find new favorite foods you love.

Tip #3: Be aware of how foods are prepared. The studies described above also suggest how we prepare the food is important. We can start out with a whole unprocessed food and end up with something no better than processed food if we prepare it incorrectly. If we add lots of cream, cheese, butter, and/or sugar, we increase the caloric density. And this can lead to us consuming more calories without even thinking about it.Throw in some salt and we have also made the food hyper-palatable, which makes us want to eat more.

Now you might be saying, “But I grew up with my food being cooked this way. This is my comfort zone. Do I have to completely change the way I cook my food, and the items I choose at my favorite restaurant?”

Again, my short answer would be, “No, but you might want to try new recipes.” I am not a cooking guru. That would be my wife. But I do know there are lots of books and web sites featuring healthy recipes. Once again, be bold. Try new recipes until you find new favorites. Try new items on your favorite restaurant’s menu or try new restaurants until you find healthier, restaurant foods you love.

Tip #4: Never say never. This is perhaps the most important tip. Whenever we tell ourselves we can never eat a food again, it becomes irresistible. We are setting ourselves up for failure. The goal should be to change unhealthy foods and unhealthy recipes from an everyday occurrence to an occasional pleasure.

The Bottom Line

Multiple studies show that eating processed foods leads to weight gain. It may be no coincidence that 60-70% of the foods Americans eat is highly processed and 60-70% of us are overweight or obese.

In the article above, I summarize recent studies asking why processed foods make us fat. If you think these studies are only of interest to scientists, you would be wrong. These studies also help us to identify unprocessed and minimally processed foods in our diet that can make us fat.

For more information on these studies, and 4 tips on how you can enjoy eating without getting fat, 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.

_____________________________________________________________________________

My posts and “Health Tips From the Professor” articles carefully avoid claims about any brand of supplement or manufacturer of supplements. However, I am often asked by representatives of supplement companies if they can share them with their customers.

My answer is, “Yes, as long as you share only the article without any additions or alterations. In particular, you should avoid adding any mention of your company or your company’s products. If you were to do that, you could be making what the FTC and FDA consider a “misleading health claim” that could result in legal action against you and the company you represent.

For more detail about FTC regulations for health claims, see this link.

https://www.ftc.gov/business-guidance/resources/health-products-compliance-guidance

Weight Gain During Pregnancy

November 14, 2023 by Dr. Steve Chaney

How Much Weight Should You Gain And Why?

Author: Carolyn Curtis, MSN, CNM, RN, FACNM, FAAN

Editor: Dr. Steve Chaney

Weight gain during pregnancy is a challenge for many women. The Centers for Disease Control has stated that 48% of women gained more than the recommended amount of weight during pregnancy, only one third (32%) of women gained the recommended amount and 21% of women gained too little[i]

Weight is a big thing to be concerned about and to work on prior to and during pregnancy. Why do you need to worry about this? One’s weight prior to pregnancy can make it more difficult to become pregnant. And weight gain during pregnancy carries lifelong implications for both the mother and infant.

Many women think that during pregnancy, that they must “Eat for Two”, thus giving them the feeling that they should eat more to nourish a developing baby. However, this saying needs to be re-examined, as I explain below.

Nutrition during pregnancy is really, really important. It lays down the physical foundation for your baby and has lifelong implications for both mother and baby. Keep in mind, you are growing a baby!

So how much weight should I gain during pregnancy? Weight gain in pregnancy will be based upon your body mass index or BMI.

What is the body mass index? The Body mass index (BMI) is a measure of body fat based on height and weight that applies to adult men and women. A calculator is used to determine your BMI. [ii] Calculators to measure BMI can be downloaded from the Apple store and Google Play.

It is going to be the determining factor for how much weight you should gain during pregnancy.

So, Based On Your BMI, How Much Weight Should You Gain During Pregnancy?

The Institute of Medicine recommends that, based upon your pre-pregnancy BMI, weight gain during pregnancy can range from zero pounds up to 40 pounds during pregnancy.

If you are underweight, weight gain between 28 and 40 pounds is recommended.

If you are at normal weight, the recommended weight gain is between 25 to 35 pounds.

If you are overweight, the recommended weight gain is 15 to 25 pounds.

And if you are obese, the weight gain is 11 to 20 pounds during your pregnancy.[i]

Recent recommendations have proposed that obesity should be broken into three different categories. BMI 1, BMI 2 and BMI 3, and that total weight gain should be limited to zero to 15 pounds gain based on these BMI categories.[ii] Research is ongoing on these recommendations.

Proposed Weight Gain Recommendations for Pregnant Women with Obesity^†
BMI Category	Current IOM Recommendations (lbs)	Proposed Recommendations (lbs)
BMI 1 (30-34.9)	11-20	5-15
BMI 2 (35-39.9)	11-20	<10
BMI 3 (≥ 40)	11-20	Maintain prepregnancy weight

J. Clin. Invest. 2019 129: 4567-4569

Where Does The Weight Go During Pregnancy?

Your baby and changes in your body during pregnancy account for the 25 to 35 pounds weight gain during pregnancy.

Baby – 6-8 pounds.

Placenta and surrounding water – 4-6 pounds.

Uterus – 2-3 pounds.

Enlarged breast tissue – 2-3 pounds.

Increased blood (blood volume increases 40% to 50% during pregnancy) – 4 pounds.

Fluids in the maternal tissue throughout your body – 2-3 pounds.

Fat stores – 5-8 pounds.

How Many Calories Should You Eat Each Day?

During the first trimester, it is recommended that women gain no more than four pounds. In the second and third trimesters of pregnancy, it is recommended that women should gain between one half pound to one pound per week[i].

One pound is equal to 3,500 calories. This equals to 500 calories per day which is equal to a sandwich and a glass of milk. This is definitely not “eating for two”. If you are carrying twins or triplets, this amount will increase.

What Happens If You Are Underweight Or Overweight?

Implications for mother and baby are as follows:

Overweight[i]

Mother:

May take longer to get pregnant.

Increased risk of miscarriage

Increased risk of developing pre-eclampsia.

Increased risk of diabetes.

Having a longer labor which can result in postpartum hemorrhage.

Increased possibility of needing to use internal monitors as external monitors cannot pick up fetal heart tone due to fat density.

Increased risk of cesarean section.

Increased risk of shoulder dystocia because the baby is also big.

Weight stays on after pregnancy, which increases the risk of overweight and obesity.

Increased risk of developing diabetes later in life.

Increased risk of repeat cesarean section.

Baby:

Increased risk of neural tube defects.

Increased risk of heart defects.

Baby is too big for weeks of pregnancy (gestational age baby).

Hyperglycemia, meaning that the baby’s blood sugar is too high.

Possibility of trauma when the baby is being born.

Long-term obesity for that child resulting in childhood obesity.

Daughters that are large for gestational age are more likely to be obese and deliver larger babies.

Underweight

Mother:

Difficulty with getting pregnant.

Increased risk of having a pre-term birth (your baby is born before 37 weeks of pregnancy).

Baby:

Increased risk for prematurity.

Increased risk that baby is small for gestational age or low birth weight.

Problems with oxygen levels at birth.

Trouble staying warm because the baby doesn’t have the fat stores that give the calories to help the baby to stay warm.

Breathing problems.

Increased problems with infection.

Nervous system problems with possible long-term effects of cerebral palsy, blindness, developmental delays where your baby is not developing on time.

What Resources Are Available To Help You Gain The Appropriate Amount Of Weight During Pregnancy?

There are many resources available, including weight gain trackers.[i] It would be wise to seek the help of a registered dietitian. If you are underweight or obese, their services may be covered under your health insurance.

The Bottom Line

Women who are overweight or underweight prior to pregnancy can have difficulty becoming pregnant.

Many women carry the idea that during pregnancy, that they are “Eating for Two”. This idea can lead to excessive weight gain for the mother that persists after pregnancy and childhood obesity for the infant.

Weight gain during pregnancy is determined by one’s pre-pregnancy body mass index (BMI).

Based upon the prepregnant BMI, weight gain during pregnancy can range from 11 pounds to 40 pounds during pregnancy. Ongoing studies are suggesting a weight gain amount of zero to 15 pounds for Obesity Categories I through III.

It is recommended that during pregnancy, mothers gain up to a total of four pounds in the first trimester and between one half to one pound per week in the second and third trimesters. This amount of weight gain equals to an additional 500 calories per day which is equal to a sandwich and one glass of whole milk additionally per day.

Weight gain during pregnancy carries lifelong implications for both mother and infant.

Seek help from a registered dietitian if you are overweight or underweight. Weight gain trackers are also available for mothers to track their weight during pregnancy at the Centers for Disease Control website.[ii]

[1] https://www.cdc.gov/reproductivehealth/maternalinfanthealth/pregnancy-weight-gain.htm

[1] https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm

[1] https://nap.nationalacademies.org/resource/12584/Resource-Page—Weight-Gain-During-Pregnancy.pdf

[1] https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2013/01/weight-gain-during-pregnancy

[1] https://nap.nationalacademies.org/resource/12584/Resource-Page—Weight-Gain-During-Pregnancy.pdf

[1] https://www.womenshealth.gov/healthy-weight/weight-fertility-and-pregnancy

[1] https://www.cdc.gov/reproductivehealth/maternalinfanthealth/pregnancy-weight-gain.htm

[1] Ibid

[i] https://www.cdc.gov/reproductivehealth/maternalinfanthealth/pregnancy-weight-gain.htm

[ii] Ibid

Visit My You Tube Channel

For more information on how to have a healthy pregnancy and healthy child, especially if you are black, visit my You Tube Channel.

https://www.youtube.com/@carolyncurtis-thecarabcompany

Carolyn Curtis

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.

About The Author

Carolyn Curtis, MSN, CNM, RN, FACNM, FAAN, has:

More than 40 years’ experience in the oversight of domestic and international programs and the provision of nursing and midwifery integrated service delivery in maternal child health, family planning, reproductive and women’s health care.
Twenty years’ experience in teaching, mentoring, and providing clinical oversight to undergraduate and graduate public health, medical, nursing and midwifery students.

Do Diet Sodas Make You Fat?

June 24, 2014 by Dr. Steve Chaney

Should You Kick the Diet Soda Habit?

Author: Dr. Stephen Chaney

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?

These, 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.