We hear all the time about the importance of eating whole foods in their most natural state (vegetables, fruit, seafood, eggs, meat, nuts, legumes, and whole grains to name a few). But for most people, the advice to choose real food is falling on deaf ears.
The ubiquitous marketing combined with the heightened taste profile and convenience of processed food is too much for most people to overcome. The threat of disease and obesity associated with diets dominated by these foods are too far off to motivate most people to make better choices.
Maybe this will make a difference: Not only is processed food associated with obesity and metabolic diseases like diabetes, research shows that diets high in processed food lead people to eat more.
Not a little more either: A new study found that subjects eating a processed food diet ate 500 more calories than when they ate a macronutrient-matched whole food diet.
This was the first randomized-controlled study to compare processed with whole food diets on eating behavior, metabolic markers, and body composition. Scientists took 20 volunteers and randomized them into a group that ate an ultra-processed diet or a group that ate a whole food diet for two weeks.
An example of the processed diet was a breakfast of Eggo pancakes, turkey sausage, tater tots, and orange juice. For the whole food diet, breakfast consisted of a spinach omelet with sweet potato hash and skim milk. Processed snack options included potato chips, goldfish crackers, and peanut butter sandwich crackers. Whole food snacks were oranges, apples, almonds, walnuts, and raisins.
The available foods were matched for fat, protein, and carbs and subjects were allowed to eat as much or as little as they wanted at each meal. After two weeks the group traded regimens.
Results showed that participants ate significantly more when their meals were ultra-processed—around 500 additional calories per day—than when they were eating unprocessed meals. About half of those extra calories came from carbohydrates and half from fat. There was no increase in protein.
The added calories in the processed diet led participants to a gain a predictable 2 pounds. In contrast, participants lost the same amount when eating the healthier whole foods diet.
Both groups reported that the diets were flavorful enough to enjoy eating. There was no difference in “pleasantness” of meals, leading researchers to theorize that the reason more calories were eaten on the unhealthy processed diet was not about meal satisfaction. Instead, they suspected that people often ate easier-to-chew processed foods faster, leading to a delay in satiety signals and greater food consumption.
Previous studies have shown how diets high in processed foods negatively impact energy expenditure. A 2010 investigation assessed the thermic effect of a processed cheese sandwich (processed cheese product and white bread) with a whole food cheese sandwich (bread with whole grain kernels and sunflower seeds and cheddar cheese). Both meals contained the same number of calories and a similar proportion of carbohydrate, protein, and fats.
The thermic effect of food is the amount of calories required to break down food, synthesize enzymes, and perform metabolic processes. It is typically about 10 percent of daily energy expenditure. Protein burns the most calories, followed by carbohydrates and then fats.
Results showed that participants burned double the calories after the whole food meal compared to the processed sandwich. Equally significant is the fact that the participants who ate the processed food meal had their metabolic rates drop below their average basal metabolic rate (BMR)—the average energy needed to keep the body functioning at rest—during the sixth hour after eating. The whole food meal group never fell below the BMR.
The reason for the dramatic difference in calorie burn for the two meal types is due to variation in the quality of the ingredients and fiber content between the two meals. The processed food meal contained refined grains without bran or germ and only about one-third of the fiber of the whole food meal. The refined quality of the processed food ingredients means it is more easily digested, ultimately burning fewer calories in the process.
Choosing whole foods in their most natural state is a simple way to lower calorie intake for better body composition and lower risk of obesity.
If you do include processed foods in your diet, focus on mindful eating. Slowing your eating rate down and savoring the food may allow for hunger-dampening messages to register in the brain.
It’s completely possible to train your taste buds to enjoy healthy whole foods. Sometimes eating healthy is about changing your habits to reach for nutritious options instead of the same old junk that has come to dominate the average American’s diet. Swap nuts for chips, berries for candy, and vegetable sticks with hummus for chicken wings.
Hall, K., et al. Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell Metabolism. 2018. 30, 67-77.
Barr, S., Wright, J. Postprandial Energy Expenditure in Whole-Food and Processed-Food Meals: Implications for Daily Energy Expenditure. Food and Nutrition Research. July 2010. 2(54), 144-150.