When discussing the causes of rising obesity rates, the usual suspects are increased intake of highly processed food, more screen time with less active time and larger portions. Even though there is not overwhelming clinical research on these causes, they have a feel of “truthiness.”
That changed recently with the publication of a paper from Kevin Hall of the National Institutes of Health (NIH). This was a one-month clinical study on the impact of highly processed foods on food intake and weight.
Ten men and 10 women lived in the metabolic ward at the NIH. They were only able to eat the test foods provided and were given meals with either ultra-processed or unprocessed foods.
They were instructed to eat as much as they wanted. The menus were designed to be matched for calorie density, fiber, sugar, sodium and vitamins and minerals. Ultra-processed food is defined as formulations mostly of inexpensive sources of dietary energy and nutrients plus additives. A processed breakfast was bagel and cream cheese with turkey bacon. One unprocessed breakfast was Greek yogurt with berries and nuts and apple slices. A processed lunch example was a cheeseburger with fries and a diet lemonade. An unprocessed lunch was baked cod with potatoes with olive oil and a side salad.
After two weeks, people eating the ultra processed foods gained almost 2 pounds. People eating unprocessed foods lost 2 pounds. Calorie intake was about 500 calories a day higher with the processed foods. Rate of eating was faster with the processed foods. Subjects rated the diets similarly on pleasantness and familiarity. They didn’t eat more because they thought it tasted better.
It was a small study of short duration, but it was well planned and executed. And it has a simple and direct message: Swap a few of the ultra-processed foods in your pantry for unprocessed ones and you might slow down, eat less and have an easier time maintaining your weight.