Many people diligently pursue healthy habits – mindful eating, regular exercise – yet find themselves frustrated by a lack of progress on the scale. New research suggests the problem may not be what we eat, but how it’s processed. A growing body of evidence indicates that highly processed foods can significantly impact metabolism, even within the context of an otherwise seemingly healthy diet.

A recent study conducted at South Dakota State University investigated the effects of food processing on weight, metabolism, and hormonal balance in 36 adults with an average age of 72 who were slightly overweight. Participants were divided into two groups, each following a diet meeting US dietary guidelines. One group consumed lean pork as their primary protein source, while the other followed a vegetarian diet rich in legumes like lentils and beans. Crucially, both diets emphasized freshly prepared meals, minimizing additives, flavor enhancers, and ready-made sauces. This resulted in a dramatic reduction in the proportion of industrially processed foods in their daily intake, falling from around 50 percent to just 13 percent.

The results were striking. Participants on the minimally processed diet automatically reduced their daily calorie intake by approximately 400 kilocalories, even though the amount of food offered remained consistent. Over eight weeks, they lost an average of four kilograms – roughly 8.8 pounds – without resorting to strict diet restrictions or experiencing feelings of hunger. Perhaps even more significant was the observed decrease in abdominal fat, which fell by an average of 13 percent.

Beyond weight loss, key metabolic markers also showed substantial improvement. Insulin levels decreased by about 20 percent, while insulin sensitivity increased by around 25 percent. LDL cholesterol levels were reduced by 10 to 12 milligrams per deciliter (approximately 0.26-0.31 mmol/L), and inflammatory markers, such as C-reactive protein (CRP), decreased significantly. These positive changes were observed in both the meat-eating and vegetarian groups, reinforcing the idea that the degree of processing, rather than specific macronutrient composition, was the driving factor.

The study also revealed significant changes in participants’ hormone levels. The hormone FGF21, which plays a role in regulating energy balance, increased by up to 50 percent. Simultaneously, levels of leptin, a hormone that controls appetite, fell by about two nanograms per milliliter. “Our data demonstrates for the first time coordinated changes in these two hormones in older people due to a low-processed diet,” explained Professor Moul Dey, the study leader. This hormonal shift suggests that the body utilizes energy more efficiently when consuming natural, unprocessed ingredients.

Further improvements were seen in cholesterol levels, with total cholesterol decreasing by 20 to 25 milligrams per deciliter and LDL cholesterol by up to 12 milligrams per deciliter, contributing to a more favorable cardiovascular profile – a particularly important consideration for older adults who often face multiple health risks.

Notably, participants found it relatively easy to adhere to the dietary plans. “They simply replaced ready-made products with freshly prepared meals,” noted Saba Vaezi, a doctoral student involved in the research. There was no need for meticulous calorie counting or complex meal planning. The weight loss was also evenly distributed, affecting not only the abdominal area but also the hips and thighs, indicating a broader positive impact on metabolism.

The benefits of a minimally processed diet appear to stem from several factors. The fiber content of vegetables and legumes promotes a longer-lasting feeling of fullness. A lower proportion of fat and sugar helps to regulate insulin and blood lipid levels. And, crucially, fresh preparation inherently reduces overall calorie intake.

However, maintaining these changes long-term proved challenging. One year after the study concluded, many participants reverted to their previous eating habits, with the proportion of highly processed foods in their diets rising back to around 44 percent – nearly as high as before the study began. Some of the positive effects were lost.

This underscores the importance of sustained effort in reducing the consumption of industrially processed products to permanently stabilize weight, insulin levels, and cholesterol. “Less processed ingredients are enough to bring the metabolism back into balance,” emphasizes Professor Dey.

The findings reinforce a growing consensus in the nutrition community: the level of food processing has a greater impact on weight and metabolic health than simply the number of calories consumed. By prioritizing whole, unprocessed foods, individuals can potentially reduce their energy intake, facilitate weight loss, and improve metabolic markers without resorting to restrictive dieting.

Recent research, published in The Guardian on August 5, 2025, echoed these findings, demonstrating that individuals following a minimally processed diet consumed 290 fewer calories per day and experienced a 2 percent reduction in body weight on average, including a notable decrease in fat mass.

A study published in Medical News Today confirmed that those consuming fewer processed foods lost twice as much weight as those with diets higher in ultra-processed options. Both groups lost weight, but the difference was significant.

research from the University of Bristol, published in Fox News on February 4, 2026, revealed that individuals on a whole-food diet consumed 57% more food by weight than those eating ultra-processed foods, yet still consumed approximately 330 fewer calories per day. This suggests a natural tendency to gravitate towards nutrient-rich, lower-calorie options when ultra-processed foods are avoided.

These findings collectively highlight the potential of shifting dietary focus from calorie restriction to prioritizing the quality and processing level of food. While more research is needed to fully understand the long-term implications, the evidence strongly suggests that embracing a diet centered around fresh, minimally processed ingredients can be a powerful strategy for improving metabolic health and achieving sustainable weight management.