Are calories in fat worse and harder to burn than calories from carbohydrates?

The difference isn't in how the calories are "burned" so much as in how excess calories are stored.

Excess carbohydrate calories must be converted to triglycerides before they can be stored as body fat. This process requires over 25% of the energy stored in the food. Thus, if you took in 100 Calories of pure carbohydrate in excess of your body's needs, you'd only store about 75 Calories worth of fat, since you used up some of the energy in the conversion process.

Fat, on the other hand, is fat to begin with. It only takes about 3% of the energy in it to put it up on the larder shelf, as it were. Thus, 100 Calories from fat in excess of your body's needs can end up as 97 Calories worth of saddlebag.

Remember that we take in nutrients of all sorts together, though - fats, carbs, and proteins. Thus, the most important factor over time is generally the total number of calories. However, if you keep the number of calories in your diet exactly the same and switch from a high-fat to a lower-fat diet you will generally notice a reduction in weight (assuming you were in caloric balance beforehand).

Also, what's the difference between fat and saturated fat? Is saturated fat just more calories concentrated? A prompt response is appreciated!

Fats come in several varieties, among them saturated, monounsaturated, and polyunsaturated. The saturated fats are named because they have all the hydrogen they can hold (i.e., they are saturated with hydrogen) and contain no double bonds in their chemical structure. The monounsaturated fats have one double bond (which could be broken by adding two hydrogen molecules), and the polyunsaturated fats have more than one double bond.

Unfortunately I'm not an expert on the subtleties of fat metabolism, but it has been well established that there is an increased risk of heart disease associated with high-fat diets, in particular those high in saturated fat. Diets high in monounsaturated fat, such as the Mediterranean diet, are thought to have a heart-protective effect, but there is still much research going on in this area.

For most healthy individuals, it's recommended that keeping total amounts of dietary fat below 30% (and having saturated fat make up no more than 10% of the total amount of fat consumed) can decrease the risk of heart disease. Individuals with different pre-existing conditions may have different nutritional requirements.

Simple sugars can pose a much greater risk to health than fats. It depends on several factors and it can become a very complicated issue - it would take a large book to completly cover this subject.

Individuals who are obese, diabetic, or have some form of impaired glucose tolerance may need to watch their ingestion of some foods, but for the general population the primary risks from sugary foods are tooth decay and obesity from an excess of calories.

For those who insist that "complex carbohydrates are better" it's important to differentiate among three areas of distinction when making any sort of argument:

• The end-products of digestion - complex carbohydrates are broken down into simple carbohydrates before absorption. All carbohydrates are converted to glucose before the body can use them for energy, or they are stored as glycogen or fat.
• The glycemic index - some carbohydrates are absorbed more quickly than others, and it is not always the foods people think that are absorbed quickest.

  Be careful with the glycemic index, though. It's really most useful in talking about foods in isolation. The truth of the matter is that people tend to eat meals made up of a combination of nutrients, and this can affect absorption time as well.

• Nutrient density - much of the problem with many "sugary" foods is a lack of nutrient density. For example, a candy cane and an apple might both have the same amount of calories, and both might get most of their calories from simple sugars. However, the apple generally has vitamins and minerals and fiber the candy cane lacks (except for those high-fiber vitamin-fortified candy canes at Bread and Circus ;-) ).

Your thoughts above are, for the most part, correct. On the subject of which would take longer to 'burn', again, there is no simple answer. If you refer to 'stored' fat and carbs - carbs can be burnt off much quicker than stored fat - also, large amounts of fat can be stored by the body but only a small amount of 'sugar'.

On the other hand unused sugar is converted into stored fat, very quickly - and the fact that the body stores very little sugar means that if it is not used quickly it will be converted into fat. Also, the body does not store fat unless insulin is released - which only happens when you eat sugar.

Fat on the other hand is calorie dense, but it digest much slower than sugars which gives you a time advantage.

larry...

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