“We live in an age of radical diets: Paleo, vegan, low-glycemic, low-carb, low-fat, high fat (keto). Which one’s best for maintaining a healthy weight? In a 2014 paper, Yale medical researchers surveyed the scientific evidence and came up with a simplifying answer: Diets consisting mainly of “minimally processed foods” point to good health outcomes, whether or not they contain foods people like to debate about, like meat or grains. For a new study published Thursday, scientists at the National Institutes of Health finally put that advice to the test.
The authors note that no study has directly compared the health impacts of diets based on the kind of highly processed boxed foods one finds at the center of the supermarket, versus those based on fruits, vegetables, and whole grains. So the NIH team assembled 20 healthy adult volunteers—10 male and 10 female—sequestered them at a research hospital for a month, and subjected them to two weeks each of meals from ultra-processed foods and minimally processed foods.
The two diets were structured to be roughly equal in calories, protein, fat, carbs, and fiber. Because highly processed foods tend to be low in fiber, the processed diet featured fiber-added beverages to make up the difference. The subjects were essentially over-served—for each of the diets, the researchers made available about 5,400 calories per day in the form of three meals and plus snacks, and allowed to eat as much or as little as they wanted.”