It is quite interesting to read articles about diet and health that were written between the 70s and 90s compared to those written in the last ten years. Our ability to measure - whether it be the items that people eat or the metabolic processes that certain foods trigger - has gotten much sharper over time. This better measurement has led to changes in what is recommended for health and left many of us confused about what to eat.
One thing has remained consistent for the last 30 years... the majority of people in developed countries are eating too much food and gaining weight because of it.
Scientists are now challenging the notion that a calorie is a calorie - even for weight gain (since we already knew that some calorie sources were bad for our health). It is very likely that the body is doing something different with foods that are high in SoFAS - saturated fats and added sugars, especially if these foods are highly processed. Refined grains tend to be high in both sat fat and sugar and even contain the dreaded trans fat.
People frequently go out to eat lunch when they are working or attending conferences. The majority of foods served in chain and fast food restaurants are calorically dense - made so from the SoFAS. YES? So, what does nearly every one say about work and presentations after lunch? "I don't want to be the presenter after lunch, everyone will fall asleep." OR, "I don't feel like doing any work, I just want to take a nap."
I used to feel that way after lunch, too. I don't now because I eat food that is not calorically dense. My meals are always low in saturated fat and added sugar. They have a low glycemic load (are not starchy). I never feel lethargic after I eat.
Think about how you feel after you next few meals. Eating too much of any food will make you uncomfortable, but eating certain foods, even reasonable portions, trigger a different kind of discomfort. I believe that the way you feel after you eat something - after the taste rush has passed - is a clue as to whether or not it was a healthy food.