I was so excited to see this study published earlier this year, because it fits in so well with my own experience, and nothing like it had been done before in such a well-controlled manner.
Most of us suspect that industrial/processed/junk foods lead to unhealthy weight gain. One proposed reason is that they tend to contain more sugar and fat than “natural” foods.
The researchers in this study wanted to test that theory, and they designed a very clever and scientifically rigorous experiment.
They created two menu plans, one built around highly processed foods and the other featuring more natural, minimally processed foods. However, the two plans were carefully matched to have equal proportions of fat, carbohydrates, protein and fiber.
Then they convinced 20 randomly selected adults to move into a National Institutes of Health laboratory for a month (!), eating all of their food there (and exercising 20 minutes three times a day on a stationary bike). They were split into two groups: one ate the highly processed food plan for two weeks, while the other group ate the minimally processed foods. Then the two groups were switched and ate the opposite diet for two weeks.
This excellent summary gives more details about how it worked:
All participants received three daily meals and were free to eat as much or as little as desired within 1 hour. Meals were designed to be well matched across diets for total calories, energy density, macronutrients, fiber, sugars, and sodium, but differed widely in the percentage of calories derived from ultra-processed vs unprocessed foods.Becky McCall, Highly Processed Food Intake Leads to Overeating and Weight Gain, Medscape Medical News, May 20, 2019
As an example, an ultra-processed breakfast might consist of a bagel with cream cheese and turkey bacon, whereas the minimally processed breakfast was oatmeal with bananas, walnuts, and skim milk.
So what happened? Fascinating and (I think) very encouraging things:
- Both groups ate all they wanted of the foods offered to them, and they both reported enjoying the food and feeling satisfied.
- When people ate as much highly processed food as they wanted, they consumed about 500 more calories per day than the whole-foods group, and they also ate more rapidly.
- The processed food group gained about 2 pounds in two weeks, and the whole foods group lost about 2 pounds.
- When the groups were switched to the other kind of food, they had the same results of gaining or losing 2 pounds. Clearly it wasn’t the people, it was the food!
Most headlines about the study emphasized the weight gain with processed foods. But the exciting part for me was the seemingly automatic fat loss among the participants eating minimally processed foods.
When I resolved to get healthier, inspired by the book Younger Next Year, I decided to eat only “real food.” Actually, as my 2014 food diary shows, I made plenty of exceptions, as I’ll explain below. But I didn’t limit the quantity of whole, natural foods; I enjoyed them until I was satisfied — and I consistently lost about a pound of excess body fat, week after week, while feeling healthier and more energetic.
News headlines about this study referred to “ultra-processed foods,” so you might imagine a menu packed with Cheese Whiz, Cool Whip and Lucky Charms (yuck!). No … it was basically typically American food, such as Cheerios, muffins, quesadillas and peanut butter and jelly sandwiches. The kinds of foods I used to eat, and then (mostly) stopped.
If you download this document, you can see all of the actual menus, complete with color photos of the meals!
Here’s a sample lunch menu for the processed-food group: Hot dog on bun with ketchup and yellow mustard, baked potato chips, cranberry juice with NutriSource fiber, blueberry yogurt with NutriSource fiber (you can see they were struggling a bit to match the diets on fiber content!).
And here’s an unprocessed lunch: Spinach salad with chicken breast; apple slices; bulgur; sunflower seeds and grapes; vinaigrette made with olive oil, fresh squeezed lemon juice, apple cider vinegar, ground mustard seed, black pepper and salt (yes, yes, yes!).
If you’re interested, I hope you’ll take the time to download the document and compare the photos of the two types of meals. The beautiful unprocessed meals, featuring a rainbow of fruits and vegetables, start on page 25.
Both groups enjoyed their food, and they ate all they wanted. The researchers found no significant differences in “pleasantness” or “familiarity” between the two diets. Likewise, scores for “hunger, fullness, satisfaction and capacity to eat” were similar. The people eating the unprocessed food felt full and satisfied. And they lost excess body fat.
That’s what happened to me too. And I didn’t even have to be 100% strict, as I can see when I review my 2014 food diary. I regularly used commercial protein shakes as meal replacements or boosters (my favorite was CalNaturale ). At events, I’d eat half a piece of cake or a bite of a donut. I enjoyed a small glass of beer or wine on occasion. But day after day, I mainly focused on enjoying all I wanted of a generous rainbow of vegetables, plenty of fruit, and meat, fish, nuts and seeds.
What I rigorously cut out were flour-based foods, which I realized are often only “carriers” (the bun carrying the hamburger, the pasta carrying the pesto, the pita chips carrying the hummus). Hence the lettuce wraps, the McDonald’s jalapeño double with no bun, and the yummy “not-chos” pictured below:
The question remains: if it wasn’t excess sugar and fat, why did the study participants eat more of the processed foods and gain weight? The main difference found by the researchers was that the people consuming highly processed food consistently ate it faster (about 17 calories more per minute). The highly processed food just seemed to go down more easily.
This points to eating slowly, and mindful eating, as an important strategy to avoid taking in more calories than our bodies need. I’ve never worked on this myself … hmm, time to start!
But of course feeding our bodies is not just about calories (or calories per minute). There are many other great reasons to nourish ourselves with a wide variety of the unprocessed whole foods our bodies evolved to enjoy. Whole plant foods are full of substances that researchers are just starting to understand, substances that feed good gut bacteria, help prevent cancer, and so much more. Losing excess body fat is just a wonderful bonus.