Losing Weight: How Ultra-processed Foods Cause Weight Gain

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We’ve all heard that if you want to lose weight, you need to avoid processed foods. There are dozens of trend diets surrounding this idea – “whole grain”, “clean eating”, “Whole30”, “all-natural”, “locally grown”, etc. According to a new study that was recently published by the National Institutes of Health (NIH), now we know why.

The Study

The study was conducted by Kevin Hall, a mathematical modeler who has become an expert in global obesity in the past decade. Hall earned himself a reputation for precise research methods, sharp analysis of outcomes, and a non-dogmatic view on the worldwide obesity crisis.

In the study, Hall investigated 20 inpatient adults who were given both ultra-processed and unprocessed diets for 14 days each. The trial was conducted in a clinical setting, limiting access to food to only what was provided, which was calibrated to contain the same amount of calories, sugars, fiber, fat, and carbohydrates.

The infamous “Twinkie diet” may spring to mind, where Mark Haub, a professor of human nutrition, set out to prove that weight loss is tied to directly to calorie deficiencies rather than nutrition by consuming only packaged junk foods, such as what one may find in convenience stores and gas stations.

However, this new study didn’t restrict the calories of the participants, nor did it use your typical junk foods. Participants were allowed to consume however much they desired. The ultra-processed diet didn’t contain a lot of chips, cookies, candies, and sodas, like the convenience store diet, but rather convenience foods such as canned soups and grains-in-a-pouch.

An example of a processed dinner used in the study. (Paule Joseph and Shavonne Pocock, NIH)
An example of an unprocessed dinner used in the study. (Paule Joseph and Shavonne Pocock, NIH)

Why Processed Foods Cause Weight Gain

The results of the study found that participants consumed 500 more calories per day when on the ultra-processed diet than when on minimally processed diets. The participants observed a 2-pound weight gain consistent with the predicted amount calculated using calorie math for the 2 weeks. Participants who started with the ultra-processed diet lost two pounds when they switched to the minimally processed diet. Participants reported that both diets were equally tasty.

So why exactly did the ultra-processed diet participants consumed more calories?

Caloric Density

These foods tend to have a higher amount of calories per mass than minimally processed foods, otherwise known as being “calorie-dense”. According to Hall, “There were about two calories per gram in the processed food and in the unprocessed it was closer to one.” One effect calorie-dense foods have on us is they can trick the visual cues we use when serving ourselves food. According to Penn State nutrition professor, Barbara Rolls, people, on average, tend to decide how much to eat by eye-balling the amount of food; the more there is available, the more they eat, and volume and weight both play a role. In fact, since Americans use volume-based servings, it’s even harder to gauge calorie-density.

So, when the food in question has a lot of calories for its size, that translates to simply consuming more. This idea part of what is called “Volumetrics”, an area that Rolls is very familiar with and has published quite a few diet books based on reducing calorie density by consuming foods with more water and fat. She posits that these diets are more effective than those that concentrate on controlling macro-nutrient intake. This is because while macro-nutrient diets aim to trigger satiety signals, the decision to stop eating should happen before those signals have time to serve their purpose.


Another possible explanation may have to do with the fact that when eating ultra-processed foods, participants consumed calories 50% faster than when eating minimally processed foods. This may be due to the tendency of ultra-processed foods to be softer and easier to consume.

The quicker we consume calories, the easier it is to overeat and consume too many calories. This is because it takes about 20 minutes for our brains to receive satiety signals sent from our gut. These signals take the form of hormones released by our gut as we consume food. The NIH study supported this, revealing more PYY (an appetite reducing hormone) and less ghrelin (a hunger hormone) in subjects eating unprocessed foods.

Combining this with the calorie-density of these foods, the rate at which you consume calories per bite goes up. You eat more calories faster.


Another key factor that may play a role in this story is that minimally-processed foods contain more insoluble fiber. This fiber doesn’t break down during digestion and can not be absorbed. This reduces caloric absorption and increases the feeling of satiety, resulting in less calorie consumption.


The final factor that comes into play is a simple fact that these foods taste better. Food manufacturers put a lot of effort into making these foods taste good. I think many of us can attest to preferring a pastry over carrots, for example.

What are ultra-processed foods?

So what foods qualify as ultra-processed? The first step to understanding what foods to avoid is to clear up the misnomer that all processed foods are bad. This is not the case. Processed foods merely refer to any alteration from its original form before consumption. This includes processes like heating, pasteurizing, skinning, canning, drying, even refrigeration by some definitions. So, unless we’re plucking apples directly off a tree or drinking milk straight from a cow, the vast majority of the foods we eat are technically processed. Undergoing a process doesn’t mean the food became unhealthy. After all, dehydrating a banana doesn’t turn it into “junk food”.

So what foods qualify as ultra-processed? The first step to understanding what foods to avoid is to clear up the misnomer that all processed foods are bad. This is not the case. Processed foods merely refer to any alteration from its original form before consumption. This includes processes like heating, pasteurizing, skinning, canning, drying, even refrigeration by some definitions. So, unless we’re plucking apples directly off a tree or drinking milk straight from a cow, the vast majority of the foods we eat are technically processed. Undergoing a process doesn’t mean the food became unhealthy. After all, dehydrating a banana doesn’t turn it into “junk food”.

The idea of ultra-processed foods is a new one. There are still many experts in the field that haven’t been convinced of its importance or what it even is. That’s what makes Hall’s study so groundbreaking. It showed a clear connection between the quality of food and weight, via a randomized, controlled trial, which is considered the “gold standard” for research seeking to establish cause-and-effect associations.

“We need to figure out what specific aspects of the ultra-processed foods affected people’s eating behavior and led them to gain weight,” Hall said. “The next step is to design similar studies with a reformulated ultra-processed diet to see if the changes can make the diet effect on calorie intake and body weight disappear.”

The term “ultra-processed food” was coined by Carlos Monteiro, a professor of Nutrition and Public Health at the University of Sao Paulo, Brazil. In 2009, Monteiro and his colleagues linked the global obesity pandemic and the related chronic diseases to harmful practices in food production. As a result, Monteiro created a classification system called NOVA that groups all foods by their degree of processing:

  • Group 1: Unprocessed or minimally processed foods – Foods derived from edible parts of nature, undergoing processes designed to prepare item for consumption, preservation, and/or storage with minimal additions, such as removal of inedible or unwanted parts, drying, crushing, grinding, fractioning, filtering, roasting, boiling, pasteurisation, refrigeration, freezing, placing in containers, vacuum packaging, or nonalcoholic fermentation.
  • Group 2: Processed culinary ingredients – These are substances obtained directly from group 1 foods or from nature by processes such as pressing, refining, grinding, milling, and spray drying. The purpose of processing here is to make products used in home and restaurant kitchens to prepare, season and cook group 1 foods and to make with them varied and enjoyable hand-made dishes, soups and broths, breads, preserves, salads, drinks, desserts, and other culinary preparations. Examples include salt mined or from seawater; sugar and molasses obtained from cane or beet; honey extracted from combs and syrup from maple trees; vegetable oils crushed from olives or seeds; butter and lard obtained from milk and pork; and starches extracted from corn and other plants.
  • Group 3: Processed foods – These are relatively simple products made by adding sugar, oil, salt, or other group 2 substances to group 1 foods. Most processed foods have two or three ingredients. Processes include various preservation or cooking methods, and, in the case of breads and cheese, non-alcoholic fermentation. The main purpose of the manufacture of processed foods is to increase the durability of group 1 foods, or to modify or enhance their sensory qualities.
  • Group 4: Ultra-processed food and drink products – These are industrial formulations typically with five or more and usually many ingredients. Such ingredients often include those also used in processed foods, such as sugar, oils, fats, salt, antioxidants, stabilizers, and preservatives. Ingredients only found in ultra-processed products include substances not commonly used in culinary preparations, and additives whose purpose is to imitate sensory qualities of group 1 foods or of culinary preparations of these foods, or to disguise undesirable sensory qualities of the final product. Group 1 foods are a small proportion of or are even absent from ultra-processed products.

For a full read on Monteiro’s food classification, you can view his work here.

If the definitions sound vague, you’d be right. There is still a lot of debate around the concept, in regards to its credibility, the boundaries of these definitions, and the exact requirements to classify something as ultra-processed. Many authorities are working toward a more workable definition, but agree that there are some common features that can point to ultra-processed.

The primary indicator of ultra-processed food is a long ingredient list. Many of these inclusions are substances not used in culinary preparations or additives used to imitate the qualities of “real” foods.

Some authorities include the addition of sugar, salt, oils, and fats to aid in flavor and preservation as part of the definition. Excess sugar, salt, and oils in the diet are known to play a role in the development of numerous health conditions. Thus it is likely that these “extras” are responsible for endangering our health – no matter how good they taste.

Check out our HueDietitian, Linn Steward’s take on the NOVA system

Why Ultra-Processed Foods Are a Problem

Processed foods are an essential part of the food industry. It was a revolutionary step in the development of our society. It’s inconceivable to think we can completely go back to a farm-to-table lifestyle. With our busy lives juggling work and family, it’s all too easy to skip making a meal from scratch in favor of a quick, ready-to-go meal.

That is a perfect example of the power of marketing. Food manufacturers spent a lot of effort, research, and money into getting people to buy these products and books such as Michael Moss’s “Salt, Sugar, Fat” and Mark Schatzker’s “The Dorito Effect” have detailed just how seriously food manufacturers take the challenge of winning consumer hearts, minds and stomachs. From misleading packaging to deceptive labels, to misinformation, like how the sugar industry shifted the blame to fat, there is a lot working against us in choosing the right products at the store.

Not only are processed foods convenient and enticing, they are also 60% cheaper, making them more accessible to the lower class. In fact, many poorer neighborhoods are experiencing a phenomenon called “food deserts”, where there is no access to fresh foods, fruits, and vegetables, only heavily treated foods with long shelf lives and low storage costs.

In short, there are so many factors that make it so hard to avoid these potentially dangerous foods.

Related Article: Looks to me like my KIND bar is ultra-processed

How to avoid ultra-processed foods

So with so much working against us, how do we reduce the presence of ultra-processed foods in our diets?

Use HueTrition’s HueApproved Scanner

We at HueTrition recognized how difficult it is to identify these naughty foods. So we created a scanner that you can use right on your phone to analyze each product before you even put it in your cart. Check it out here.

Learn How to Read a Label

The first step to understanding what we are eating is learning how to read a nutrition label and learning what to look for. Read this post, for more details on what to look for on a label.

Shop Wisely

When shopping for products, look for products with lower calorie account per serving. Avoid calorie-dense products. For example, nuts may seem like a great snack to binge on, since there are many health benefits to adding nuts to your diet. But those delicious buggers are quite calorie-dense. Just 1 cup of walnuts has 523 calories, and it’s not even the most calorie-dense nut. Since they are so small and easy to eat, it’s very easy to overeat.

Check the serving size. This can make a huge difference in the number of calories we consume. Make sure that the serving size is not deceptively small or misleading. For example, a quick glance at the packaging of a pop tart, claims about 200 calories per serving, which is not bad for a snack. But if you look closely, you’ll note that the serving size is only one pop tart, even though they come in a package of two. I think many of us know how easy it is to finish off a package of pop tarts once you open them.

Next, look for products that have a higher nutrient ratio. The more nutrients in the item, the less food you need to consume in order to maintain healthy levels of nutrition.

Look for higher volume foods like vegetables, popcorn, chia seeds, yogurt, and oatmeal. These foods help you feel full and prevent you from overeating.

Look for foods that contain a lot of fiber. Fiber is a great little trick to avoid overeating. Fiber can slow down digestion, reduce caloric absorption, and increase the feeling of satiety.

Shop the perimeter. Sticking to the outer rim of the store will help you stay away from ultra-processed foods and help you choose fresh, minimally-processed food, due to how grocery stores organize their products.

Do More Home Cooking.

Not only can eating out have a negative effect on your wallet, but it can also have one on your waistband too. This is because most restaurants are more preoccupied with pleasing the palate instead of watching the calorie count. This means generous portions of fats and sugars or ultra-processed ingredients. By cooking at home you can reduce the calorie count of a dish by 50%! Not that there’s anything wrong with splurging every once in a while.

Don’t know where to start? Sign up with one of our HueChefs. They will get you started learning a few dishes, along with an ingredient list and one-on-one live instruction in your kitchen.

Meal Prep

Meal prepping is the practice of cooking and preparing your future meals. Doing so gives you control over what you put in your tummy through the week in an easy and convenient way. So instead of reaching for an ultra-processed, ready-made meal, you already have a minimally-processed meal ready to go.

Eat Slower

As mentioned earlier, it takes 20 minutes for the satiety signals to reach your brain. If you take your time, finish each bite before starting the next, wait 5 minutes before going for seconds, you give your body more time to let you know when you are full and prevent yourself from overeating.

Swap for healthier alternatives

Once you can identify ultra-processed foods, simply swapping them out for healthier alternatives will make a huge difference. Here is a chart of common foods and their healthier alternatives:

Ultra-processed Processed Homemade
sweetened breakfast cereals plain bran cereal oatmeal made with rolled oats and sweetened with honey
Coke artificially flavored sparkling water Homemade carbonated drinks using products like the SodaStream
flavored potato chips plain tortilla chips DIY pita chips
white bread whole-wheat bread with minimal ingredients homemade bread
fried chicken deli rotisserie chicken roast chicken from scratch
flavored candy bar with long ingredient list simple candy bar with short ingredient list dark chocolate squares
Frappuccino store-bought cold brew drip coffee
mashed potato flakes, or instant mashed potato frozen potatoes fresh, whole potatoes
energy drink sweetened fruit juice fresh-squeezed orange juice
flavored granola bars with added sugar and preservatives granola bars with minimal additives DIY granola
artificially flavored cheese crackers naturally flavored crackers whole-grain crackers and cheese slices

Chart provided by  Healthline


Thanks to the efforts of Hall, Monteiro, and many others, we now know the risks of ultra-processed foods and how to identify them. If we can cut down the amount of ultra-processed foods in our diet, we can make a real difference in our lives and in the food industry. If we can encourage the food industry to look to making products that are formulated specifically to be more nutritious or healthful, then maybe we can turn the tide on this obesity pandemic. As always, we get the food supply we demand.

We know that diet culture has taught us what foods have been socially labeled as “bad” and “good.” But it’s really not so straight-forward. While we are still in the process of understanding ultra-processed foods, what qualifies and how they affect us, the first step is understanding that food is more than fuel or a craving; it’s a relationship. So, the next time you head to the grocery store, take a moment to think about how what you add to your cart will affect you. Choose the foods you want in your diet, and eat them in their whole or minimally processed form: Apples instead of apple juice, whole oats instead of commercial granolas, fresh or frozen turkey breast instead of packaged turkey bacon or lunch slices, and so on.

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Kevin D. Hall, Alexis Ayuketah, Robert Brychta, …, Peter J. Walter, Shanna Yang, Megan Zhou. “Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake”.  Cell Metabolism. May 16, 2019. https://www.cell.com/cell-metabolism/pdf/S1550-4131(19)30248-7.pdf

“NIH study finds heavily processed foods cause overeating and weight gain”.  National Institutes of Health. May 16, 2019. https://www.nih.gov/news-events/news-releases/nih-study-finds-heavily-processed-foods-cause-overeating-weight-gain

Amby Burfoot. “It’s trendy to scorn processed food. Now there’s research to back up that attitude.”. The Washington Post. June 24, 2019.  https://www.washingtonpost.com/lifestyle/wellness/its-trendy-to-scorn-processed-food-now-theres-research-to-back-up-that-attitude/2019/06/21/d19f54d8-929d-11e9-aadb-74e6b2b46f6a_story.html

Tamar Haspel, Food Columnist. “How processed food makes us fat”. The Washington Post. July 17, 2019. https://www.washingtonpost.com/lifestyle/food/how-processed-food-makes-us-fat/2019/07/17/2bf93a2c-a7ff-11e9-86dd-d7f0e60391e9_story.html

“Soluble vs. insoluble fiber”, Medline Plus, https://medlineplus.gov/ency/article/002136.htm

Sarah Garone, NDTR. “What’s the Difference Between Processed and Ultra-Processed Food?”.  Healthline.  October 18, 2018.  https://www.healthline.com/health/food-nutrition/ultra-processed-foods

Madison Park. “Twinkie diet helps nutrition professor lose 27 pounds”.  CNN, November 8, 2010. http://www.cnn.com/2010/HEALTH/11/08/twinkie.diet.professor/index.html

Carlos A. Monteiro, et. al. “The Food System: Food classification. Public health. NOVA. The star shines bright”.  World Public Health Nutrition Association. March 2016.  https://archive.wphna.org/wp-content/uploads/2016/01/WN-2016-7-1-3-28-38-Monteiro-Cannon-Levy-et-al-NOVA.pdf

2 thoughts on “Losing Weight: How Ultra-processed Foods Cause Weight Gain

  1. Thanks for Weight Loss article. Hey Author, Thanks for the valuable information. I have been looking for this since long time. I have not read such beautiful article in a long time. Exploring rest articles. Thanks

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