So the study asked them to consume 1500 extra calories per day? Regardless of the source, that’s a confounding variable right there. I’d like to see this done again with a steady calorie count and just a different source for those calories. Personally, if I go nuts on the junk foods for a meal I typically find myself compensating by eating less of my normal, healthier diet.
the issue is volume though. ~3500 calories of “healthy” foods will be physically harder to consume than 2000 calories of healthy foods and 1500 calories of calorically dense food.