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Why Processed Food May Be Piling On The Pounds


We are hearing about ultra-processed foods at the moment and how they maybe affecting our health and weight. In general terms, I like to think about ultra-processed food as the kind of foods we couldn’t make in our own kitchen. In my time I’ve had a look around many a food factory where some processes are very simple – take the Christmas Pudding factory for instance – where the recipe and method are simply scaled up from what we may do in our own kitchen. In contrast, the manufacturing process for a humble cheese flavoured snack aka Wotsits consists of a blend that is extruded, expanded, coated and dried – not a process we could easily recreate in our own home. The same could be said for the type of fries we find in drive thru’s where they look very different from a finely cut potato.


For some time, it has been hypothesised that this ultra-processed food has been contributing to weight gain and associated diseases such as diabetes, cardiovascular diseases and some cancers. As we know most nutritional science studies are based on population studies over time so it is always interesting to see the results of a gold standard randomised control trial where we can compare the test v placebo.

In the US they put together a randomised control trial comparing ultra-processed and unprocessed diets. In 2019 Kevin Hall asked 20 volunteers to stay at a clinical research hospital in Bethesda where they would be fed a diet of only ultra-processed or whole foods for two weeks, then switch to the other diet for the subsequent two weeks. Those on the ultra-processed diet were fed a selection of dishes including tater tots, turkey sausage, Spam, and lashings of diet lemonade. The wholefood diet was mostly made up of fruit, vegetables, and unprocessed meat. For both diets, Hall and his researchers provided double the recommended portions of food so participants could eat as much as they liked. The critical part, however, was that the two diets were nutritionally matched, so each contained roughly the same amount of protein, fat, carbohydrates, fibre, and so on.


The results of the study surprised Hall. On the ultra-processed diet, people ate around 500 extra calories per day and put on about two pounds. When people were on the wholefood diet, they ate fewer calories and lost weight—this is despite the fact that the meals on offer had roughly the same nutrient compositions. To Hall, this implied that there was something other than salt, sugar, and fat content that was causing people to eat excess calories and gain weight. Again, it leads us to think there is more to food than its constituent parts.


Though a small study based on highly processed food Hall’s study drew a link between processed food and excess calorie consumption, but it can’t tell us why people on the ultra-processed diet ate more. After he published the results, Hall was flooded with suggestions from other scientists. Some thought it was because junk food is more calorie-dense. Since processed foods are often deep-fried and high in fat, they pack in more calories per gram than whole foods. Or maybe it was because ultra-processed food, was eaten more quickly. To understand this, we only have to think about how long it would take to eat a baked potato compared to fast food french fries. Less or no cutlery is involved and a lot less chewing. This theory was backed up in the study as those on the ultra-processed diet ate significantly faster than those eating whole foods, maybe not allowing their tummies to send out the typical physical and hormonal signals of satiety. Other scientists thought that additives might be playing a role, or that processed food changed the gut microbiome in a way that influenced calorie intake. Another factor might be the effect that ultra-processed foods have on our brain where the food components may interact with the brain’s reward systems.


Though only an initial trial Dr Hall will no doubt be establishing further trials to try to discover a deeper understanding of how ultra-processed foods maybe affecting our weight and optimum nutrition. In the meantime, we may be wise to moderate the types of processed foods we could not create in our own kitchen and place the spotlight on a diet of wholefoods, fruit, veggies, lean meats, fish, seafood and low fat dairy for a healthy weight.


If you would like help achieving your optimum nutrition, losing weight or improving your gut health please contact me.


Happy Eating.


Nina Thomas

Registered Associate Nutritionist & Food Scientist

Bridgford & Bingham Nutrition


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