Now, a study shows, 21% of women and 10% of men in Generation X and the tail end of the Baby Boom generation, now in their 50s and early 60s, meet criteria for addiction to these ultra-processed foods.

That rate is far higher than it is among adults who grew up just a decade or two earlier, and only encountered ultra-processed foods in adulthood. Among adults age 65 to 80, just 12% of women and 4% of men meet criteria for ultra-processed food addiction.

The study, published in the journal Addiction by a team from the University of Michigan, is based on nationally representative data from more than 2,000 older Americans surveyed by the U-M National Poll on Healthy Aging.

The poll is based at the U-M Institute for Healthcare Policy and Innovation and supported by Michigan Medicine, U-M's academic medical center. The new paper builds on a previous poll report by diving deeper into generational differences and correlations with health.

Measuring food addiction in an under-studied group

The researchers used the modified Yale Food Addiction Scale 2.0 (mYFAS 2.0), a standardized tool adapted from the criteria used to diagnose substance use disorders. The scale asks about 13 experiences with ultraprocessed foods and drinks that define addiction, such as strong cravings, repeated unsuccessful attempts to cut down, withdrawal symptoms, and avoiding social activities because of fear of overeating.

In this case, the "substance" is not alcohol or nicotine, but highly rewarding ultra-processed foods such as sweets, fast food, and sugary beverages. By applying clinical addiction criteria to ultra-processed foods, the study highlights the ways in which such foods can "hook" people.

"We hope this study fills a gap in knowledge about addiction to ultra-processed foods among older adults, as measured by a well-studied and standardized scale," said Lucy K. Loch, a graduate student in the U-M Department of Psychology. "Today's older adults were in a key developmental period when our nation's food environment changed. With other research showing clear links between consumption of these foods and risk of chronic disease and premature death, it's important to study addiction to ultra-processed foods in this age group."

Differences by gender

Unlike traditional substance use disorders -- which historically have been more common in older men -- ultra-processed food addiction shows the opposite pattern: higher prevalence in older women.

One explanation may be the aggressive marketing of "diet" ultra-processed food to women in the 1980s.

Low-fat cookies, microwaveable meals, and other carbohydrate-heavy products were promoted as weight-control solutions, but their engineered nutrient profiles may have reinforced addictive eating patterns.

Women now aged 50 to 64 may have been exposed to ultraprocessed foods during a sensitive developmental window, which may help explain the poll's findings for this age group, said senior author Ashley Gearhardt, Ph.D., a professor of psychology at U-M and member of IHPI. Gearhardt leads the U-M Food and Addiction Science & Treatment Lab.

"The percentages we see in these data far outpace the percentages of older adults with problematic use of other addictive substances, such as alcohol and tobacco," said Gearhardt. "We also see a clear association with health and social isolation, with much higher risks of ultra-processed food addiction in those who call their mental or physical health status fair or poor, or say they sometimes or often feel isolated from others."

Key findings related to overweight, health status and social isolation

• Overweight self-perception:

Women aged 50 to 80 who said they are overweight were more than 11 times as likely to meet criteria for ultra-processed food addiction than women who say their weight is about right. Men who reported being overweight were 19 times as likely. No matter what their age, 33% of women who described themselves as overweight, 13% of women who described themselves as slightly overweight and 17% of men who described themselves as overweight met criteria for addiction to ultra-processed foods. Of the total sample, 31% of women and 26% of men in the sample said they were overweight and 40% of women and 39% of men said they were slightly overweight.

• Health status:

Men reporting fair or poor mental health were four times as likely to meet criteria for ultra-processed food addiction; women were nearly three times as likely. For physical health, men reporting fair or poor health were three times as likely to meet criteria for ultra-processed food addiction, and women were nearly two times as likely.

• Social isolation: Men and women who reported feeling isolated some of the time or often were more than three times as likely to meet criteria for ultra-processed food addiction as those who did not report isolation.

The researchers suggest that individuals who perceive themselves as overweight may be particularly vulnerable to "health-washed" ultra-processed foods - those marketed as low-fat, low-calorie, high-protein or high-fiber, but still formulated to amplify their appeal and maximize craving.

"These products are sold as health foods - which can be especially problematic for those trying to reduce the number of calories they consume," Gearhardt said. "This especially affects women, because of the societal pressure around weight."

Looking Ahead

The generation of older adults now in their 50s and early 60s is the first to live most of their lifespan in a food environment dominated by ultra-processed foods, Geahardt noted.

"These findings raise urgent questions about whether there are critical developmental windows when exposure to ultra-processed foods is especially risky for addiction vulnerability," she said. "Children and adolescents today consume even higher proportions of calories from ultra-processed foods than today's middle-aged adults did in their youth. If current trends continue, future generations may show even higher rates of ultra-processed food addiction later in life."

She added, "Just as with other substances, intervening early may be essential to reducing long-term addiction risk across the lifespan."

About the study

The study was funded by a National Science Foundation Graduate Research Fellowship Program (DGE-2241144) and the National Institute on Drug Abuse of the National Institutes of Health (5R01DA055027).

In addition to Loch and Gearhardt, the study's co-authors are Matthias Kirch, M.S., Dianne C. Singer, M.P.H, Erica Solway, Ph.D., M.S.W., M.P.H., J. Scott Roberts, Ph.D. and poll director Jeffrey T. Kullgren, M.D., M.P.H., M.S. Roberts is a member of the faculty at the U-M School of Public Health, and Kullgren is a member of the faculty in the U-M Medical School and a primary care physician at the VA Ann Arbor Healthcare System.

"These are diseases that are growing increasingly common and that have a poor prognosis if detected late," says Rickard Strandberg, affiliated researcher at Karolinska Institutet's Department of Medicine in Huddinge, who has developed the test with his departmental colleague Hannes Hagström. "Our method can predict the risk of severe liver disease within 10 years and is based on three simple routine blood tests."

For the study, the researchers at Karolinska Institutet in Sweden and their colleagues in Finland evaluated how well the method can estimate the risk of severe liver disease. The model, which is called CORE, was produced with advanced statistical methods and is based on five factors: age, sex and levels of three common liver enzymes (AST, ALT and GGT), which are commonly measured during regular health checks.

A web-based calculator

Their aim has been to produce a tool that is easy to use in primary care, where most patients first seek medical attention. A web-based calculator is already available for doctors and nurses at www.core-model.com^[1].

"This is an important step towards being able to offer early screening for liver disease in primary care," says principal investigator Hannes Hagström, adjunct professor at Karolinska Institutet's Department of Medicine in Huddinge, and senior consultant at Karolinska University Hospital. "Drug treatment is now available, soon hopefully also in Sweden, for treating people at a high risk of developing liver diseases such as cirrhosis or liver cancer."

The study is based on data from over 480,000 people in Stockholm who underwent health checks between 1985 and 1996. On following the participants for up to 30 years, the researchers could see that some 1.5 per cent developed severe liver disease, such as liver cirrhosis and liver cancer, or required a liver transplant.

Highly accurate risk prediction

The CORE model proved highly accurate and was able to differentiate between people who either did or did not develop the disease in 88 per cent of cases, which is an improvement on the currently recommended FIB-4 method.

"Primary care hasn't had the tools to detect the risk of severe liver disease in time," says Professor Hagström. "FIB-4 is not suited for the general population and is less effective at predicting the future risk of severe liver disease."

The model was also tested on two other population groups in Finland and the UK, where it again demonstrated a high accuracy in predicting this risk. The researchers make the point, however, that it needs to be further tested on groups at especially high risk, such as people with type 2 diabetes or obesity. They also recognise a need to integrate the model into medical records systems to facilitate its clinical use.

The study was a collaboration between Karolinska Institutet, Helsinki University Hospital, Helsinki University and the Finnish Institute for Health and Welfare. It was financed by the Swedish Research Council, Region Stockholm (CIMED) and the Swedish Cancer Society. Hannes Hagström is engaged in several collaborations with the pharmaceutical industry regarding liver disease prognosis, but none that is relevant to the current study.

The findings, published in the journal Nature Microbiology, could lead to new treatments for bacterial infections - especially urgent since drug-resistant infections already kill more than a million people a year.

Polymyxins were discovered more than 80 years ago and are used as a last-resort treatment for infections caused by "Gram negative" bacteria. These bacteria have an outer surface layer that acts like armor and prevents certain antibiotics from penetrating the cell. Polymyxins are known to target this outer layer, but how they disrupt it and then kill bacteria is still not understood.

In the new study, the research team revealed in high-resolution images and biochemical experiments how the antibiotic Polymyxin B rapidly caused bumps and bulges to break out on the surface of an E. coli bacterial cell.

These protrusions, which appeared within minutes, were followed by the bacterium rapidly shedding its outer armor.

The antibiotic, the researchers concluded, had triggered the cell to produce and shed its armor. The more the cell tried to make new amor, the more it lost the amor it was making, at such a rate that it left gaps in its defenses, allowing the antibiotic to enter the cell and kill it.

However, the team found that this process - protrusions, fast production and shedding of armor, and cell death - only occurred when the cell was active. In dormant (sleeping) bacteria, armor production is switched off, making the antibiotic ineffective.

Co-senior author Dr Andrew Edwards, from Imperial, said: "For decades we've assumed that antibiotics that target bacterial armor were able to kill the microbes in any state, whether they're actively replicating or they were dormant. But this isn't the case. Through capturing these incredible images of single cells, we've been able to show that this class of antibiotics only work with help from the bacterium, and if the cells go into a hibernation-like state, the drugs no longer work -- which is very surprising."

Becoming dormant allows bacteria to survive unfavorable conditions such as a lack of food. They can stay dormant for many years and "wake up" when conditions become more favorable. This can allow bacteria to survive against antibiotics, for instance, and reawaken to cause recurrent infections in the body.

Co-senior author Professor Bart Hoogenboom, based at the London Centre for Nanotechnology at UCL, said: "Polymyxins are an important line of defense against Gram-negative bacteria, which cause many deadly drug-resistant infections. It is important we understand how they work.

"Our next challenge is to use these findings to make the antibiotics more effective. One strategy might be to combine polymyxin treatment - counterintuitively - with treatments that promote armor production and/or wake up 'sleeping' bacteria so these cells can be eliminated too.

"Our work also shows we need to take into account what state bacteria are in when we are assessing the effectiveness of antibiotics."

The E. coli cells were imaged at the London Centre for Nanotechnology at UCL. A tiny needle, only a few nanometers wide, was run over the bacterial cell, "feeling" the shape to create an image (a technique called atomic force microscopy) at much higher resolution than would be possible using light.

Co-author Carolina Borrelli, a PhD student at the London Centre for Nanotechnology at UCL, said: "It was incredible seeing the effect of the antibiotic at the bacterial surface in real-time. Our images of the bacteria directly show how much polymyxins can compromise the bacterial armor. It is as if the cell is forced to produce 'bricks' for its outer wall at such a rate that this wall becomes disrupted, allowing the antibiotic to infiltrate."

The team compared how active (growing) and inactive E. coli cells responded to polymyxin B in the lab, finding that the antibiotic efficiently eliminated active cells but did not kill dormant cells.

They also tested the E. coli cells' response with and without access to sugar (a food source that wakes up dormant cells). When sugar was present, the antibiotic killed previously dormant cells, but only after a delay of 15 minutes - the time needed for the bacteria to consume the sugar and resume production of its outer armor.

In conditions where the antibiotic was effective, the researchers detected more armor being released from the bacteria. They also observed the bulges occurring across the surface of the cell.

In conditions where it was ineffective, the antibiotic bound itself to the outer membrane but caused little damage.

Co-author Dr Ed Douglas, from Imperial, said: "We observed that disruption of the outermost armor of the bacteria only occurred when the bacteria were consuming sugar. Once we knew that, we could quickly figure out what was happening."

Co-author Professor Boyan Bonev, of the University of Nottingham, said: "Working together has given us unique insights into bacterial physiology and morphology under stress that have remained hidden for decades. Now we understand better the weak points of bacteria."

This work was funded by the Biotechnology and Biological Sciences Research Council (BBSRC) and the Engineering and Physical Sciences Research Council (EPSRC), parts of UK Research and Innovation, and by Wellcome.