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A simple solution?
It's not surprising that people lose weight, lower
cholesterol, and lower blood pressure when following a low carbohydrate, lower
calorie diet. High carbohydrate, low calorie diets will do the same thing. Any
diet that restricts calories will cause weight loss, a reduction in cholesterol,
and a lowering of blood pressure. It's the loss of body fat caused by the
reduction in calories, not the composition of the diet that causes this.
What's most important when evaluating the risks/benefits of a diet is what
happens when the diet is consumed at maintenance calories, when the body is not
in a state of fat loss due to caloric restriction.
Low carbohydrate diets fall in and out of fashion, and have gained
a lot of attention recently, with the added twist of the glycemic index. Like
many other popular dietary approaches, these diets take an extreme approach by
limiting one type of food and focusing on it as the sole source of obesity and
other chronic metabolic disorders. It would be great to have a simple solution!
 To understand
what a low carbohydrate diet is, one needs a very basic understanding of the sources of
calories in the diet. There are four nutrients that provide calories:
carbohydrates, fats, proteins, and alcohol. Carbohydrates are essential in
maintaining healthy activity of the sympathetic nervous system and in preventing
ketosis, a condition that occurs when the body must breakdown ingested fat for
fuel because of a lack of carbohydrate. Ketosis is a potentially dangerous
condition that produces the breakdown of bone, among other things.
Carbohydrates are the body's primary source of
energy, and are quickly and easily converted to blood glucose, the body cells'
preferred source of fuel. In particular, the brain must have glucose as a source
of energy. The brain will not use other sources of energy except in the extreme
case of starvation, in which ketone bodies (from the breakdown of body fat) are
used by the brain. The body cannot store a large amount of carbohydrate; there
is only a short supply available as glycogen in the liver and muscle.
Therefore, carbohydrates must be supplied on a regular basis.
So, we need a certain amount of carbohydrate to prevent ketosis,
but where does it come from? Carbohydrates include sugars, starches, and fiber.
Foods that contain mostly carbohydrate are grains, cereals, beans, fruits, and
vegetables. Sugar and flour are forms of carbohydrate, so any food made with
sugar (like soda pop) or flour (breads, pasta, bakery goods, cookies, crackers,
etc.) are sources of carbohydrate as well.
Do Low Carbohydrate Diets Work?
Those who advocate severe carbohydrate restriction point to
the relationship between ingesting carbohydrate and the insulin response.
Insulin is a vital hormone that regulates the entry of glucose to the cells,
helps the body store fat, and at high levels, is associated with damage of the
arterial walls. Carbohydrate ingestion stimulates insulin production. The
problem is that the more insulin is produced, the more resistant the cells can
become to insulin, so the blood glucose can't enter the cells as easily, and
blood glucose and circulating insulin levels remain high, causing damage.
 The problem is that insulin resistance
is not caused by simply
ingesting carbohydrates, and is not completely solved by
eliminating them. Insulin resistance has a very strong genetic component, and is
heavily influenced by level of physical fitness and the degree of body fatness.
Generally, the more fit a person is, the less resistant they are to
insulin, and the more body fat a person has, the more resistant they are to
insulin. So the real answer to solving insulin resistance (and many other health
problems) may be to maintain a healthy body at a healthy weight, not to severely
restrict the body's main source of fuel. In other words, reducing calories, not
just reducing carbohydrates may be the best solution.
Severe restriction of carbohydrates
leaves fat, protein, and alcohol left to supply calories. What are the effects?
- In the absence of weight loss, diets high in
fat damage arteries and promote heart disease in the long term.
- Diets high in protein, especially animal
protein, are very hard on kidneys, causing them to work too hard to remove the
waste products of protein metabolism.
- Diets high in animal foods are higher on the
food chain, so you're consuming whatever chemicals, pesticides and hormones the
animals were fed to make them fat or were in their food (even fish).
- By severely limiting carbohydrates, you are
restricted from many plant foods (not just the green stuff) which contain
protective factors against cancer, heart disease and other chronic diseases.
While I advocate restricting junky, low
nutrition carbohydrate sources like chips, crackers, cakes, cookies, soda
pop, etc., I recommend replacing those foods with other high nutrition, high
fiber carbohydrates (vegetables, beans, whole grains, fruit) instead of
replacing those calories with high fat, high protein animal foods or high fat
foods. This keeps the composition of a healthy diet around 30% fat, 20% protein,
and 50% carbohydrate and accomplishes the goal of improved nutrition.
Depending upon the calorie level you are given, this diet can cause weight loss,
weight gain, or weight maintenance. With good guidance on making the best
choices for protein, fat and carbohydrate foods, you'll accomplish your personal
health and fitness goals and you'll have a diet you can follow long term. Limiting the "junk" carbohydrates to special occasions will help
with keeping carbohydrate intake in proper perspective. Choosing carbohydrates
that digest more slowly or eating quickly digesting carbohydrates with other
foods is another consideration and has to do with the glycemic index, which will
be addressed as a separate topic.
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