In my last post, I reviewed a study that highlighted the beneficial effects of eating more protein. Today I want to review another study that highlights the benefits of limiting processed food in the diet.
A few years ago, a well known researcher at the NIH named Kevin Hall designed a clever experiment. He got a group of 20 healthy young people to agree to live in confinement for several weeks so that he could feed them different diets and study their responses.
He then broke the volunteers into two groups of 10 people each. Both groups were given a “buffet” style spread at each meal that was designed to be equally matched for fat, protein, carbs, fiber, sugar, and salt. There was only one difference between the two buffets.
Group one received all of their food in the form of whole, unprocessed, foods such as meat, fish, eggs, beans, fruits, nuts, and vegetables. Group two received all of their food in the form of processed foods, such as crackers, supermarket breads, frozen style dinners, protein bars, and the like.
Both groups were told to eat as much or as little as they wanted and to not make any effort to either gain or lose weight.
What was the outcome? The group that ate processed foods averaged 500 calories more per day than the group that ate unprocessed foods, and they gained a small amount of weight during the study, whereas the unprocessed foods group lost a bit of weight.
Dr. Hall then stopped the experiment at two weeks and had the two groups switch places. He again got the same results: the group that was switched from unprocessed to processed foods started to eat about 500 calories more per day, and began putting on weight, whereas the group that switched to eating unprocessed foods spontaneously cut back their intake by about 500 calories and started losing weight.
There has long been a debate in the diet world about whether the type of food you eat is the main driver of weight gain/loss, or if in the end it all comes down to “calories in versus calories out.” For example, proponents of the keto diet will often suggest that it doesn’t pay to count calories at all, because eliminating virtually all carbohydrates in your diet will automatically lead to weight loss. By contrast, the famous “twinkie experiment” (in which a college professor ate nothing but Twinkies for ten weeks and lost weight) is an example of a contrasting piece of data that suggests, no matter what you are eating, you will lose weight if your calories are restricted enough.
But I think this study helps to support both arguments. It certainly suggests that there is a difference in outcomes when eating a processed v. “Natural” foods diet, but that we don’t need to throw out the concept of calories entirely to explain this difference, because it may simply be that the reason processed foods are so fattening is that they entice us to eat more calories than we need.
Regardless, this study certainly suggests that if you want to lose weight, one of the simplest and most effective ways to do so is to cut processed foods out of your diet as much as you possibly can.
