Weight loss faster without ultra-processed foods

Diet regimes based around minimally processed ingredients can lead to twice the rate of weight loss compared with food plans containing ultraprocessed constituents, a new study has revealed.

Subjects lost significantly more weight, and dropped their fat mass and BMI to a much greater extent when they consumed a minimally processed food (MPF) rich diet compared with an equivalent meal plan based around ultra-processed ingredients.

Anecdotally, the participants also reported feeling less hungry after the MPF-based meals, despite actually consuming fewer daily calories than when on the UPF diet.

Both diets are considered “healthy” in the eyes of the Eatwell Guide, a visual tool used to define UK government recommendations on healthy eating and achieving a balanced diet. Critically, current dietary guidelines do not distinguish between minimally-processed and ultraprocessed food constituents. It’s this disparity that the new study, which is published in Nature Medicine and lead by UCL-based scientist Sam Dicken, sought to address. 

The trial recruited 55 overweight and obese adults who were fed meals prepared in accordance with the UK Eatwell guide. Critically, one of the groups were fed meals made using minimally processed ingredients, while the other group ate more ultraprocessed products. After 8 weeks, they switched around, so each participant effectively became their own control and, following a month-long “washout” period, ate the other diet plan for a further 8 weeks.

The participants ended up in an average calorie deficit compared to baseline on both diets. Intriguingly, though, although both groups were allowed to eat as much as they wanted, the MPF group consumed far less and shed more pounds.

But was this just because the subjects found the MPF-dominated diet less palatable, the study team wondered? While subjects did report a greater craving for UPFs over MPFs, the participants nevertheless enjoyed both diets equivalently.

All participants were sent ready-to-eat meals, snacks and drinks for both diets. This eliminates some of the behavioural factors involved in choice of diet. UPFs are synonymous with ease of preparation and convenience, while making meals from simple, non-processed ingredients often takes much longer.

This is a factor Dicken wants to explore moving forward. A second part of the study is already underway, working with a behavioural science team to see if participants can implement healthier dieting choices within their current environments.

The outcomes of this study raise particular concern for low income families who have less financial freedom to make choices around their intake of UPFs. Healthier foods are more than twice the price per calorie than less healthy foods; they’re also, according to the Broken Plate Report conducted by the food foundation, much less readily available. For the most deprived fifth of households, those with children would have to spend 70% of their disposable income on the government-recommended healthy diet.

Dicken is calling upon the government to help tackle this issue. “We need high level action from governments to change the financial drivers that dominate our food supply,” he says.