On November 13, 2025, two major studies published in leading scientific journals have brought renewed focus to the complex relationship between what we eat and our long-term health, particularly for younger adults and women under 50. The first, led by researchers at Newcastle University in the UK and published in the European Journal of Nutrition, delved into how different protein sources at breakfast affect satiety hormones and subsequent food intake. The second, conducted by a team at Massachusetts General Hospital and published in JAMA Oncology, linked high consumption of ultra-processed foods (UPFs) to an increased risk of abnormal bowel growths in women under 50, a potential precursor to cancer.
The Newcastle study set out with a timely question: can plant-based proteins, touted for their sustainability and ethical benefits, match animal-based proteins in keeping people feeling full and possibly reducing calorie intake later in the day? According to News-Medical.net, the research team recruited 18 healthy adults, including both younger individuals (aged 18 to 35) and older participants (over 65), to take part in a meticulously controlled crossover trial. Each person attended the lab three times, having fasted after a standardized evening meal and abstained from caffeine, alcohol, and exercise. On each occasion, they were given one of three breakfasts: a plant-based high-protein drink (30 grams of protein, 7.8 grams of fiber), an animal-based high-protein meal (30 grams of protein, 4.5 grams of fiber), or a low-protein, high-carbohydrate meal.
Researchers measured participants’ subjective appetite using visual analogue scales and took blood samples at regular intervals for four hours after breakfast. This allowed them to track levels of peptide YY (PYY) and glucagon-like peptide 1 (GLP-1), two hormones closely linked to feelings of fullness. After the final blood draw, everyone was offered an ad libitum pasta lunch—meaning they could eat as much as they wanted—to see if the breakfast’s effects lingered into the next meal.
The results were intriguing. Both high-protein breakfasts—whether plant-based or animal-based—prompted stronger satiety hormone responses than the low-protein, high-carb meal. GLP-1 and PYY levels were significantly higher following both high-protein options, with no meaningful difference between plant and animal sources. Appetite ratings fell significantly after the plant-based drink and showed a downward trend after the animal-based meal, though the changes were modest. In fact, most differences were below the 15-millimeter threshold considered necessary to meaningfully influence eating behavior, according to the study authors.
Perhaps most surprising, neither high-protein breakfast led to reduced calorie intake at lunch. Energy consumption at the midday meal was virtually identical regardless of what participants had eaten for breakfast. The study also found no significant differences between younger and older adults, though the authors cautioned that the small sample size for older participants limited their ability to detect age-related effects.
“Overall, both high-protein breakfasts promoted greater satiety hormone responses and appetite suppression than the low-protein meal, but did not affect later food intake,” the researchers concluded, as reported by News-Medical.net. They further noted that plant-based proteins can effectively replace animal proteins in supporting satiety, making them a practical and sustainable breakfast option. However, they acknowledged several limitations, including the small size of the older adult group and the absence of solid plant-based or liquid animal-based meal conditions, which could help isolate the effects of food form and protein source.
Meanwhile, across the Atlantic, the Massachusetts General Hospital team was digging into a different dietary concern: the impact of ultra-processed foods on the risk of developing bowel abnormalities in women under 50. Ultra-processed foods—think packaged snacks, sugary drinks, and ready-to-eat meals—are typically high in saturated fat, sugar, salt, and additives, and low in whole foods, fiber, and vitamins. While there’s ongoing debate about whether all UPFs are inherently unhealthy, mounting evidence links them to a range of health problems, from heart disease to early death.
The study, as detailed by The Guardian, analyzed data from 29,105 female participants in the long-running US Nurses’ Health Study II. These women, born between 1947 and 1964, completed detailed food questionnaires every four years from 1991 onward and underwent colonoscopies during the follow-up period, which lasted until June 2015. By then, all participants had reached the age of 50. The researchers focused on cases of early-onset conventional adenomas—abnormal bowel growths that can develop into cancer—and serrated lesions, another type of polyp.
The findings were sobering. Women in the highest quintile of UPF consumption, averaging 9.9 servings per day, had a 45% greater risk of developing early-onset conventional adenomas compared to those in the lowest quintile, who averaged 3.3 servings daily. This association held even after adjusting for factors like body mass index, smoking, and physical activity. However, there was no significant link between UPF intake and serrated lesions. In total, 1,189 cases of early-onset conventional adenomas and 1,598 cases of serrated lesions were recorded among the participants.
Lead author Dr. Andrew Chan explained the motivation behind the research: “The vast majority of these polyps do not become bowel cancer. But at the same time, we know the vast majority of bowel cancers we see in young people arise from these precursor lesions.” He emphasized that the study does not suggest eating UPFs makes cancer inevitable, but rather that it adds another piece to the puzzle of rising bowel cancer rates among younger people.
Possible explanations for the link include UPFs’ association with metabolic disorders like obesity and type 2 diabetes, which are themselves risk factors for bowel cancer. Dr. Chan also pointed to the potential for UPFs to promote chronic inflammation or disrupt the gut microbiome and gut lining. However, the study had its limitations: it relied on self-reported dietary data, faced challenges in classifying foods as UPFs, did not directly measure cancer development, and could not prove causation.
Fiona Osgun, head of health information at Cancer Research UK, weighed in on the findings, noting that while the study didn’t directly measure cancer risk, it “offered a useful insight into how diet might influence early changes in the bowel that sometimes led to cancer.” She also highlighted the importance of broader policy measures to make healthy diets more accessible, adding, “Our overall diet matters more for cancer risk than any single food type.”
Taken together, these two studies underscore the complexity of nutrition science. While high-protein breakfasts—regardless of whether the protein comes from plants or animals—can boost satiety hormones, they don’t necessarily reduce calorie intake later in the day. Meanwhile, diets high in ultra-processed foods appear to raise the risk of developing precancerous bowel growths in younger women, though the picture is far from simple. Both research teams call for more studies to clarify these relationships and help guide practical, sustainable dietary choices for people of all ages.
As scientific understanding continues to evolve, one thing is clear: the foods we choose each day may quietly shape our health in ways we’re only just beginning to unravel.
