How ultra processed foods make you fat
If you replace all non-intensively processed foods in your diet with ready-made ultra processed foods, you will eat 500 kilocalories more every day than if you only eat non-intensively processed foods. This is shown by an experimental study that American physiologist Kevin Hall published in Cell Metabolism.
Hall and his colleagues had 20 healthy weight subjects eat exclusively ultra processed foods foods for two weeks, and on another occasion gave the same subjects only foods that had not been processed intensively.
Ultra processed foods are ready-to-eat or almost ready-to-eat foods. They are produced at temperatures that are significantly higher than the temperatures in pans on an ordinary stove, often contain little fiber and a lot of salt, and are full of quickly absorbed carbohydrates and bad fats. Examples of ultra processed foods are hamburgers, croissants, soft drinks and juices, mashed potatoes, sausages and pizzas.
Although ultra processed foods are unhealthy in countless ways, more than half of the Western diet consists of ultra processed foods. Nutritionists suspect that the rise of ultra processed foods has caused the obesity epidemic. Hall wanted to investigate whether that is really the case.
During the two weeks that the subjects ate ultra processed foods, the subjects gained half a kilo of fat mass. If they ate only non-intensively processed foods for two weeks, they lost half a kilo of body fat.
The test subjects ate more if their diet consisted exclusively of ultra processed foods. Including snacks, the subjects then consumed around 500 kilocalories more. Those extra calories consisted of carbohydrates and fats.
A possible way in which ultra processed foods increased food intake is shown above. The test subjects ate faster if their meals consisted of ultra processed foods. Because saturation processes need time, ultra processed foods can encourage overeating, Hall suspects.
"Though we examined a small group, results from this tightly controlled experiment showed a clear and consistent difference between the two diets",
Hall says in a press release. [sciencedaily.com May 16, 2019] "This is the first study to demonstrate causality - that ultra-processed foods cause people to eat too many calories and gain weight."
Cell Metab. 2019 May 10. pii: S1550-4131(19)30248-7. doi: 10.1016/j.cmet.2019.05.008. [Epub ahead of print].
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