Ultra-processed foods 'delay satiety signals', causing weight gain

Ultra-processed foods 'delay satiety signals', causing weight gain

Ultra-processed foods 'delay satiety signals', causing people to eat 54 times more sugar

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By Sally Robertson, B.Sc.May 23 2019Reviewed by Kate Anderton, B.Sc. (Editor)

A trial conducted at the National Institutes of Health Clinical Center suggests that people who follow a diet composed of ultra-processed foods consume more calories than those who eat unprocessed foods. Even when an ultra-processed and unprocessed diet were matched for calories and nutrients, people consumed more calories on an unprocessed diet.

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The increased availability and consumption of ultra-processed foods have been associated with rising obesity rates. For decades, the wellness industry has claimed that eating more whole foods and less processed foods is an effective weight loss strategy.

However, until now, scientists have been unable to prove that consuming ultra-processed foods causes weight gain, obesity, and negative health outcomes.

Processed foods cause people to eat 54 times more sugar and 508 more calories

As recently reported in the journal Cell Metabolism, Kevin Hall from The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and colleagues set out to investigate by conducting the first randomized controlled study looking at whether a cause-effect relationship exists between weight gain and ultra-processed or unprocessed diets.

Twenty participants were randomly assigned to either follow an unprocessed diet composed of three meals per day plus snacks for two weeks or to follow a diet made up of ultra-processed foods for the same amount of time. After the two weeks were up, the groups were switched and participants followed the opposite diet for a further two weeks.

The ultra-processed breakfasts comprised Honey Nut Cheerios, margarine, a packaged blueberry muffin and whole milk with added fiber, while the unprocessed diet consisted of a Greek yoghurt parfait with fruit, nuts, olive oil and salt.

The team made sure that meals eaten on the two diets were matched for presented calories, sugar, fat, fiber, sodium, sugar, and macronutrients. Participants were asked to eat as much or as little as they liked during each meal time.

By the end of the study, Hall and team found that participants had consumed significantly more calories when they had followed an ultra-processed diet, compared with the unprocessed diet.

On the ultra-processed diet, people ate an average of 508 more calories per day (kcal/day), which was accounted for by increased energy intake from carbohydrates and fat, but not protein.  On the ultra-processed diet, participants ate 54 times more sugar and 1.8 times more fat.

The increased energy intake on the processed diet was correlated with a two-pound weight gain, compared with a two-pound loss in weight when people were on the unprocessed diet. Furthermore, those who followed the processed diet had an increase in body fat mass of almost one pound.

The participants said they enjoyed following both diets, which meant taste could be eliminated as the reason for those on the processed diet having a higher calorie intake.  The difference in energy intake was also not associated with any difference in appetite, taste of the food or familiarity with one of the diets in particular.

The team thinks that one reason calorie intake was higher on the processed diet is that people tend to eat the meals more quickly, leading them to eat more food before they feel full.

It is possible that ultra-processed foods are easier to chew and swallow, softer, and that this could delay the satiety signals. More studies are needed to determine if the consistency and density of the foods, how easy they are to eat, are important drivers of the total amount of food consumed.”

Kevin Hall, Study Author

What are ultra-processed foods?

Ultra-processed foods are foods which have been subjected to various manufacturing processes including extrusion, milling and molding, for example. They are highly manipulated and have many extra ingredients added.

Examples of these foods include candy, chocolate, soft drinks, pizza, ice-cream, packaged soups, sweetened cereals, hot dogs and chicken nuggets. The more of these types of food a person eats, the greater the likelihood that their overall nutritional intake will be poor.

How to cut back on processed foods

Top tips from health experts regarding how to cut pack on these foods include the following:

• Cook at home more often without using ultra-processed ingredients rather than grabbing something to eat whilst out.
• Dine with family and friends. Studies have shown that people who eat together have healthier eating habits such as putting more vegetables on their plate, consuming fewer soft drinks and eating less deep-fried foods.
• Make healthier choices when eating out. Ultra-processed options on the menu can be avoided and replaced with fresh and healthy choices by ensuring more vegetables are ordered and food items are poached, grilled or baked, for example, rather than deep-fried.
• Thinking about where a particular food item comes from… and if figuring out where a food may have originated seems too difficult, consider that it may be so manipulated that it provides no nourishment at all.
• Be wary of hype. Many food marketing and advertising companies label ultra-processed foods as natural, healthy or organic. While such words may refer to the original ingredients used, they do not take into account the food manufacturing process.

Journal Reference:

Hall, K., et al. (2019). Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell. doi.org/10.1016/j.cmet.2019.05.008.