Research

Minimally-Processed Foods Confer Greater Weight Loss Benefits: Study

The degree of food processing itself, not just nutrients, plays a role in weight management, according to a study from University College London researchers.

Author Image

By: Mike Montemarano

Associate Editor, Nutraceuticals World

Photo: New Africa | Adobe Stock

A study published in Nature Medicine found that people who were assigned to eat minimally-processed foods (MPF) lost twice as much weight as those who ate a diet high in ultra-processed foods (UPF).

The clinical study split 55 adults into two groups: one group was assigned an MPF diet, with foods like overnight oats or homemade spaghetti Bolognese. The other group was assigned to consume UPFs, like breakfast oat bars or a lasagna ready meal. After a 4-week washout period, both groups crossed over to try the other respective diet for 8 weeks.  

Importantly, both diets had matching levels of fat, saturated fat, protein, carbohydrate, salt, and fiber, and recommended servings of fruits and vegetables. They were designed in accordance with the UK’s Eatwell Guide, a government guidance on healthy, balanced diets. Both groups were provided with more food than they needed, and were told to eat as much or as little as they wanted, as they would normally.

While both groups lost weight, likely because both diets had an improved nutritional profile compared to their normal diet, the MPF diet resulted in nearly double the lost weight (-2.06% body weight) compared to the UPF diet (-1.05%).

On average, participants on the MPF diet achieved a deficit of 290 calories per day, versus 120 calories on the UPF diet, in reference to the Eatwell Guide, which recommends 2,000 calories per day for women and 2,500 for men.

The greater weight loss from the MPF diet came from losses in fat mass and total body water, with no change in muscle or fat-free mass, indicating improved body composition. Therefore, when observing recommended dietary guidelines, choosing minimally processed foods may be more effective for losing weight, the authors concluded.

“Previous research has linked ultra-processed foods with poor health outcomes,” said Samuel Dicken, PhD, first author of the study. “But not all ultra-processed foods are inherently unhealthy based on their nutritional profile. The main aim of this trial was to fill crucial gaps in our knowledge about the role of food processing in the context of existing dietary guidance, and how it affects health outcomes such as weight, blood pressure and body composition, as well as experiential factors like food cravings.”

While both groups saw a significant reduction in weight, it was nearly double in the MPF diet. “Though a 2% reduction may not seem very big, that is only over eight weeks and without people trying to actively reduce their intake. If we scaled these results up over the course of a year, we’d expect to see a 13% weight reduction in men and a 9% reduction in women on the minimally processed diet, but only a 4% weight reduction in men and 5% in women after the ultra-processed diet. Over time, this would start to become a big difference.”

Based on food questionnaires, MPF dieting resulted in significantly greater improvements to the number of cravings and the ability to resist them, even in spite of greater weight loss, which was expected to lead to stronger cravings. By grading the questionnaires, researchers found that MPF dieting resulted in a two-fold greater improvement in overall craving control, a four-fold greater improvement in craving control for savory food, and an almost two-fold greater improvement in resisting whichever food they most craved.

“The global food system at the moment drives diet-related poor health and obesity, particularly because of the wide availability of cheap, unhealthy food. This study highlights the importance of ultra-processing in driving health outcomes in addition to the role of nutrients like fat, salt, and sugar. It underlines the need to shift the policy focus away from individual drivers of obesity, such as the influence of multinational food companies in shaping unhealthy food environments,” said Chris van Tulleken, professor and author of the study from the University College London’s division of infection and immunity and UCL Hospital. “Stakeholders across disciplines and organizations must work together and focus on wider policy actions that improve our food environment, such as warning labels, marketing restrictions, progressive taxation and subsidies, to ensure that healthy diets are affordable, available and desirable for all.”

Generally, there weren’t any significant differences in secondary outcomes like markers of like liver function, glucose, cholesterol, or inflammation. However, longer studies would be needed to investigate these measures properly, the researchers noted.

Less than one percent of the UK population follows all recommendations of the Eatwell Guide, and most people stick to fewer than half.

“The normal diets of the trial participants tended to be outside national nutritional guidelines and included an above average proportion of UPF, which may help to explain why switching to a trial diet consisting entirely of UPF, but that was nutritionally balanced, resulted in neutral or slightly favourable changes to some secondary health markers,” said Rachel batterham, professor and senior author of the study from the UCL Center for Obesity Research. “The best advice to people would be to stick as closely to nutritional guidelines as they can by moderating overall energy intake, limiting intake of salt, sugar and saturated fat, and prioritizing high-fiber foods such as fruits, vegetables, pulses and nuts. Choosing less processed options such as whole foods and cooking from scratch, rather than ultra-processed, packaged foods or ready meals, is likely to offer additional benefits in terms of body weight, body composition and overall health.”

Keep Up With Our Content. Subscribe To Nutraceuticals World Newsletters