Ever since Taylors time and motion studies (if not earlier) we've known that if people are being observed they tend to behave differently. I don't see why that

Ever since Taylors time and motion studies (if not earlier) we've known that if people are being observed they tend to behave differently. I don't see why that wouldn't also apply to diets also. That could involve avoiding ultraprocessed foods, or it could involve having a healthy drink with your meal, having a salad or whatever.