Inexpensive, easy-to-prepare, ultra-processed foods can make you fat, which is a bummer since they often taste good and require so little prep. Who among us doesn’t like fast food like chicken nuggets and fries; ready-made meals like frozen pizzas and microwaveable dinners; or snacks such as chips, candy, ice cream and sweetened breakfast cereals. Yum, right?

Those foods (and I use the term loosely) go through multiple processes (extrusion, molding, milling, etc.), and contain many added ingredients (sugar, salt, fat additives, preservatives and artificial colors) that make them less nutritious and more unhealthy.

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The Experiment

The findings were the result of a one-month study of 20 healthy adult volunteers at the National Institutes of Health Clinical Centers. This experiment found that people ate significantly more calories and therefore gained more weight when they were fed a diet that was high in ultra-processed foods.

Researchers studied 10 men and 10 women. They were broken into two groups. The first group received ultra-processed food for 2 weeks and then home-made meals for 2 weeks. The second group received the same but in reverse order.

Meals presented were matched for calories, sugar, fat, fiber, carbohydrates and macronutrients. For example, the unprocessed breakfast might be oatmeal with bananas, walnuts and skim milk, while the processed breakfast consisted of a bagel with cream cheese and turkey bacon.

The gender of the participants, the order of their diet assignment, and their body mass index did not influence the varying calories each participant ate on each diet. And participants exercised about the same amount each day throughout the study.

Who Ate More?

Study participants were allowed to eat as much or as little as they wanted. What researchers found was that when the participants were on the ultra-processed diet, they tended to eat more, consuming an average of 508 more calories a day than when they were on the unprocessed diet.

It’s not surprising then that the same group tended to gain weight (an average of about 2 pounds in 2 weeks). And when on the unprocessed diet, they lost weight (an average of about 1 pound in 2 weeks).

Feeling Full, Or Not

Researchers wanted to understand why participants on the ultra-processed diet ate more. They came up with three reasons:

  1. Satiety Hormone – When eating highly-processed foods, the hormone that causes hunger became elevated while the satiety hormone appeared to be suppressed. As a result, people consumed more of the processed foods and more calories in order to feel full.
  2. Protein Needs – Nutritional science suggests that people eat until they have ingested the amount of protein the body needs. The researchers made sure that both meals – highly processed and unprocessed – had the same amount of protein.

    However, the highly-processed products were much more calorie dense. Thus, the participants unknowingly consumed a higher amount of carbohydrates and fat to reach their desired protein level than the group that received homemade meals.
  3. Faster Consumption – Researchers observed that participants ate faster when they were on the highly processed food diet versus eating homemade meals. They surmised that because the consistency of the processed food was softer and therefore required less chewing, the subjects consumed the food more quickly.

    Faster eating means less time for the body to react and produce the satiety signals that help you to feel full, which leads to overeating.

Cooking for Yourself Is Worth the Effort

The study concluded that limiting consumption of ultra-processed foods may be an effective strategy for obesity prevention and treatment. So what does this mean for you? If you want to minimize your intake of processed food, aim to do more food prep and cooking at home. Choose foods that are nutritious. Base meals on fresh, whole foods including vegetables, beans and whole grains.

People who frequently cook meals at home have more control over the ingredients and therefore eat healthier and consume fewer calories than those who cook infrequently. Limiting consumption of ultra-processed foods is an effective strategy for obesity prevention and treatment.

Whether you choose to go low carb, low fat, vegan, keto, or paleo for your weight-loss journey, all of these diets have one thing in common – preparing your own food, and using unprocessed or minimally processed ingredients, is best for your health and your weight. Don’t know what to cook? Our Vida180 nutrition experts will put together a diet plan for you with simple recipes. Get started now with your free diet analysis!