Are calories in fat worse and harder to burn than calories from
From: Larry DeLuca, EdM,
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
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.
This tired old saw has been trotted out by quack doctors and complementary
health practitioners for ages, but there's really not much evidence
(from our understanding of either carbohydrate metabolism or the
pathophysiology of cardiovascular disease or diabetes) to support the
statement with respect to healthy individuals.
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
- 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
- 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'.
Tehnically this is correct, in that the reactions involved in metabolizing
carbohydrates can occur faster, but in reality it makes little practical
difference, as the shifts in metabolic activity are so dynamic.
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.
Insulin is always present in the bloodstream - just in varying amounts.
There is no "on/off" switch to insulin, fat metabolism, fat storage,
or any of these processes. They all occur simultaneously, with new fat
being added to body fat stores while some body fat already stored is
being broken down.
Fat on the other hand is calorie dense, but it digest much slower than
sugars which gives you a time advantage.
What sort of time advantage? It is true that ingestion of fat simultaneously
with carbohydrate can slow the absorption of carbohydrate into the
bloodstream, and may be helpful for some people who have an exaggerated
response to pure carbohydrate, but it's really not going to be the
miraculous controlling factor in weight management, either.
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