Here's more detailed info about why having too much fruit (and carbs) can put the brakes on your fat-burning ability:
Most fruits contain high amounts of fructose. Fructose is a 5-carbon sugar compared to glucose which is a 6-carbon sugar. Even though it is low-GI, it is important not to have more than 2 pieces of fruit a day.
The reason for this recommendation is because fructose is easily convereted into fat by the liver because it skips one of the regulatory steps in carbohydrate metabolism.
When carbs are consumed it may be used for energy or stored in the body. The body has the ability to store carbohydrates as glycogen in the muscles and the liver. However, once these storage sites are full, if any more carbohydrate is consumed it is converted into fat. The enzyme responsibile for storing carbohydrate as glycogen is phosofructokinase (PFK) and fructose does not get influenced by this enzyme. As a result, it becomes easier to convert fructose into fat if excess amounts are consumed, especially all in one meal.
Overall, people who want to lose weight should have slightly less carbohydrates in their diet (around 30-40%) compared to standard recommendations, which suggests people have at least 50% of their overall calorie intake in the form of carbs.
By simply doing a little bit of research, especially if you do a Google search for: 'USDA Food Pyramid History', you will realise the impact large food organizations have in influencing government, academic and general nutritional recommendations. That is why a high carb diet has been recommended for years. Not because it is the best for health and/ or weight loss but because it helps support the economy!
Overall, once you understand how the body resonds to carbohydrate consumption, with insulin production, etc. it becomes clear that a high carb consumption is definitely not the best way to lose fat. Also, simply consider the diets of competitive bodybuilders, people who achieve 2-5% body fat levels. Sure they have carbs, but they tend to have far more protein in their diet.
In saying all of this, it certainly doesn't mean you need to follow a low-carb diet to get results and in fact it is not recommended because they are too hard to stick to long term and may result in nutritional deficiencies. However, it is important to be aware of your source of carbohydrates if you are serious about getting the best possible results from your weight-loss efforts. This means having more low-density carbs (fibrous vegetables), a moderate amount of medium-denisty carbs (fruit, starchy vegetables and dairy products) and a small amount of high-density carbs (bread, pasta, rice, cereals, etc.).
I hope this helps to make the area of fruit consumption and carb consumption much clearer.
Last edited by EvilWombatQueen
on Sat Sep 18, 2010 8:02 pm, edited 1 time in total.
Reason: Advertising links are not allowed in signatures.