There is an old saying that even "Elixir" can become a poison when consumed in unlimited quantity. Same is true with food also. The root cause of many modern day life style diseases has been attributed to processed foods with high degree of refining where bulk of the health promoting constituents are removed. A diet not balanced in terms of essential nutrients can also be a deterrent to sound health as being seen with many wealthy consumers who eat rich foods but some what unbalanced vis-a-vis one or the other nutrient vital for normal body metabolism. In India Mango is a much liked fruit but it is also rich in sugar and one of the regular observations made by physicians is that many diabetic people land into problem during Mango season because of high sugar levels in the blood caused by too much consumption of Mango. Those counting their calories must be aware of the calories contributed by fruits though these protective foods are recommended by nutrition experts. Same is true with other recommended foods like coarse grains, whole grains etc all of which do contribute to calories and their excess consumption does not help the cause of weight control. Here is an interesting commentary by a discerning observer about the implications of over consumption.
People often make the mistake of thinking that something is good for you just because it's all-natural or organic. Today, I want to focus on a different nutritional blind-spot: quality vs. quantity. Even when a food is good for you, it doesn't necessarily follow that you can eat it in unlimited quantities. Whole grains and fresh fruits are two examples of healthy foods that can easily be over-consumed.
It is true the concepts of Cosmic Index (GI) and Glycemic Load (GL) are excellent to guide consumers regarding the quality of carbohydrate in a diet but ultimately one has to control the quantity consumed to prevent excess calorie build up which can add to the waist line. When it comes to planning a diet for a normally healthy individual and others handicapped by disorders like diabetes, obesity etc different yardsticks need to be used but the basic principle that over delivery of calorie rich foods to any one can be deleterious to both the groups. Moderation and elf-discipline in eating are the corner stones for a normal healthy life.