Ultra-processed versus minimally processed foods for weight

Have you ever wondered how the type of food you eat—whether it is highly processed or closer to its natural form—might affect your health, even if you are following a healthy eating plan? Recent research published in Nature Medicine (Ultraprocessed or minimally processed diets following healthy dietary guidelines on weight and cardiometabolic health: a randomized, crossover trial) has some answers that may surprise you, and they are important for anyone interested in nutrition, health AI, and the advice we get about food.

Why does food processing matter?

Ultra-processed foods (UPF) are products like packaged snacks, sugary cereals, ready meals, and fizzy drinks. They are made mostly from ingredients you would not find in your kitchen, with lots of additives and little resemblance to their original ingredients. Minimally processed foods (MPF), on the other hand, are much closer to whole foods—think fresh fruits, vegetables, whole grains, eggs, and plain meats.

Many people in the UK and around the world eat a lot of UPF every day. In fact, more than half of the average energy intake in the UK comes from these foods. Scientists have noticed that higher UPF intake is linked to health problems like obesity, heart disease, and diabetes. But until recently, no one had done a clinical trial to see what happens if you eat mostly UPF—even if you follow healthy eating guidelines.

The new study: testing UPF versus MPF

Researchers in England set up a careful experiment with 55 adults who were overweight or living with obesity. Everyone was given two different diets for 8 weeks each—one diet was full of minimally processed foods, and the other was made up of ultra-processed foods. Both diets followed the UK's Eatwell Guide, which recommends eating lots of fruits, veggies, and whole grains and keeping salt, sugar, and fat low.

The volunteers could eat as much as they wanted from either diet, and all their meals were provided to them. Scientists measured their weight, body fat, cravings, and other health markers before and after each diet.

Results: not all healthy diets are equal

The results were clear: both diets led to some weight loss, but people lost more weight on the minimally processed food diet. On average, participants lost about 2% of their body weight on the MPF diet, compared to just over 1% on the UPF diet. That might not sound like a huge difference, but over a year, it could add up to a lot more—up to 9–13% weight loss on the MPF diet, versus only 4–5% on the UPF diet for some people.

The MPF diet also led to greater loss of body fat and better control over food cravings. Interestingly, even though the UPF diet was designed to be healthy and matched for nutrients, it was still more energy dense (more calories in each bite) and less effective for weight and fat loss. These findings help explain why eating more whole foods can make it easier to manage weight, even if you are following healthy guidelines.

Beyond weight: what about other health markers?

While both diets showed some improvements in cholesterol and blood sugar, the minimally processed food diet was especially good at lowering triglyceride levels—a type of fat in the blood linked to heart disease risk. This connects to recent health AI research discussed in Slothwise's article about new ways to reduce heart disease risk by targeting blood fats. Interestingly, the study found that cravings for sweet and savory foods dropped more on the MPF diet. This suggests that whole foods may help people feel more satisfied and less likely to overeat. For parents or doctors interested in children's health, a related Slothwise article explains how body shape and inflammation can affect blood pressure in young people—showing how important diet is for health at all ages.

What it means for patients and families

If you are trying to lose weight or just want to eat healthier, this study shows that the kinds of foods you choose matter, not just the nutrients they contain. Eating more minimally processed foods—fresh fruits, vegetables, grains, and lean proteins—can help you lose more weight and body fat than eating lots of ultra-processed foods, even if those processed foods are labeled as "healthy" or meet government guidelines.

It is also a reminder to look beyond the packaging and focus on the real ingredients in your meals. Health AI tools like Slothwise can help you track your food and understand more about what you are eating, but the basics still matter: the closer a food is to its natural state, the better it is likely to be for your health.

Takeaways for the future of healthy eating

This trial is an important step in understanding how food processing affects weight and health. While more research is needed, especially for longer periods and different age groups, the message is clear: making small changes to include more whole foods and fewer ultra-processed ones can have a big impact on your health journey.

So next time you are in the grocery store, try to fill your basket with foods that look like they did when they came out of the ground, off the tree, or from the farm. Your body (and future you) will thank you!