If you've ever tried to lose weight, you've probably been told that cooking your own meals is the way to go. This has been backed up by a recent study, which found that people who ate home-cooked, minimally processed foods lost twice the weight to those who ate mainly ultra-processed, ready-made foods.
Author
- Aisling Pigott
Lecturer, Dietetics, Cardiff Metropolitan University
The recent study , which was published in Nature Medicine, involved 50 adults who were randomly assigned to eat either a diet high in ultra-processed foods or one with mostly minimally-processed foods. Both diets were designed to meet the UK's national dietary guidelines .
Both groups lost weight, which makes sense as they consumed fewer calories than they usually did. However, the group that consumed mostly minimally processed foods ultimately consumed fewer calories overall - thereby losing more weight. They also saw slightly greater improvements to other measures of their health, such as having lower fat mass, reduced triglyceride levels (linked to heart health) and fewer cravings for unhealthy foods at the end of the study.
The ultra-processed foods group still lost weight and saw some improvements in blood lipids (fat) and blood glucose (sugar), but these changes were generally smaller than those seen in the minimally processed foods group.
As a dietitian, this is both an interesting and important piece of research - even though the results are not entirely surprising. In fact, a surprising result is that the consumption of ultra-processed food still resulted in weight loss.
The minimally processed diet group consumed fewer calories overall, which would explain why this group lost more weight. But the fact that this group saw greater improvements in other areas of their health highlights how health encompasses far more than calories or a number on the scales.
Why processing matters
Despite the bad press, food processing plays an essential role in food safety and preservation.
But how much processing a food has undergone seems to be the factor associated with worse health outcomes . These foods tend to have less fibre, more added fats, sugars and salt. This is because they're designed to be tasty and long-lasting .
The most common definition of an ultra-processed foods are foods which are industrially produced and which contain extracts of original foods alongside additives and industrial ingredients. Think crisps or frozen ready meals.
The food system in much of the world has become increasingly reliant on ultra-processed foods, with these foods contributing to about half of food intake in the UK, Europe and the US . But there's clear evidence that high intake of ultra-processed foods is linked with poorer health outcomes , including obesity, type 2 diabetes, heart disease and certain cancers.
The more calorie-rich, less nutritious foods we consume, the more our health will suffer - as this recent study has confirmed. But how can you work out which foods are classified as "ultra-processed" and which are only "minimally processed"? In short, this depends on how much processing a food product has undergone to be ready for consumption.
Ultra-processed foods are industrially formulated products made mostly from ingredients extracted from foods (such as oils, starches and proteins) and additives.
Examples include: sugary breakfast cereals, flavoured yoghurts with sweeteners and thickeners, soft drinks, instant noodles, packaged biscuits and cakes, mass-produced bread with emulsifiers and reconstituted meat products - such as chicken nuggets.
Minimally processed foods are whole foods that are altered only to make them safer or easier to prepare. Importantly, this processing doesn't change their nutritional value.
Examples include: fresh, frozen or bagged vegetables and fruit, plain yoghurt or milk, whole grains (such as oats or brown rice), eggs, fresh or frozen fish, and tinned beans or tomatoes without added sugar or salt.
Including minimally processed foods
It can sometimes feel overwhelming to work out whether a food is ultra-processed or minimally processed.
Some advice that is often suggested for working out whether a food is ultra-processed include checking to see if a product contains more than five to ten ingredients and considering if it contains ingredients you wouldn't use at home.
In addition to the number of ingredients, it's also the type of ingredients that matter. Ultra-processed foods often contain added sugars, refined starches, emulsifiers, stabilisers and flavourings that serve cosmetic purposes (such as improving colour, texture or taste), rather than preserving the food's freshness or safety.
Minimally processed foods will not contain these types of ingredients, nor will they have as many ingredients on their label.
It's also important to be aware of smoked meats . While this is a common preservation method, most commercially available smoked meats - such as bacon, ham or sausages - are considered ultra-processed because of the curing agents and other additives they contain. While plain smoked fish (such as smoked salmon) is still classed as a processed food, it uses fewer curing agents and additives than other smoked meat products.
A diet rich in minimally processed foods usually means more fibre, more nutrients and fewer calories - all of which can support weight and long-term health, as this recent study showed. So if you're keen to include more minimally processed foods in your diet, here are a few tips to help you get more onto your plate:
- build meals around vegetables, whole grains and pulses
- use tinned or frozen products for convenience and to save time while cooking
- choose plain dairy products without sugar or fruit purees, then add your own fruits, nuts and seeds for flavour
- healthy meals don't have to be complicated. Aim to include a protein source, a wholegrain carbohydrate and plenty of veggies or fruits at each meal
- batch cook meals when you have time and freeze them if possible.
As a dietitian, it's important to point out that there's a distinction between the potential harms of excessive consumption of ultra-processed foods and the essential role processing can play in ensuring food safety, preservation and accessibility.
It's also important not to panic about enjoying the occasional biscuit or ready meal, and we should avoid demonising convenience foods - especially for those who face barriers such as limited mobility or lack of cooking facilities. Because remember, the group that ate a diet high in ultra-processed foods but met dietary guidelines still lost weight and saw health benefits in the study.
Eating well doesn't mean that you need to completely eliminate ultra-processed foods. But shifting the balance towards eating more minimally processed foods, with more home-cooked meals where possible, is a step in the right direction.
Aisling Pigott receives funding from Research Capacity Building Collaborative (RCBC) / Health and Care Research Wales (HCRW)
