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Carbohydrate Confusion Q & A

Q: What role do carbohydrates play in an overall healthy diet?

A:  Dietary carbohydrates that are not required immediately for energy are
converted to glycogen, the only storage form of carbohydrate in the human
body, and stored as the most readily available energy (calories) in muscles
and in the liver. Some carbohydrates, which are used as glucose in the body,
are necessary for the body to be able to "burn" or oxidize fat (in the form
of fatty acids) for energy, the body's system for using fat for energy
(calories). If no carbohydrate is available for this and for other
carbohydrate needs of the body, protein, in the form of amino acids, is
stripped of nitrogen and the carbon skeleton is converted to glucose in the
liver. This is a life-preserving mechanism, however, it takes away from the
body's valuable protein stores. Ann M. Coulston, M.S., R.D., F.A.D.A.

Q: What does the average person need to know about carbohydrates in their
diet?

A:  Carbohydrates are the primary macronutrient fuel source for the body.
While protein and fat can be utilized as fuel, carbohydrates are most
readily converted into glucose in the blood. For a balanced diet,
carbohydrates should supply slightly over half of one's calories for the
day. Carbohydrates often are referred to as "simple" or "complex". Simple
carbohydrates are sugars, for example: fructose (in fruit), sucrose (table
sugar), and lactose (in milk). Complex carbohydrates are starches, found in
foods like potatoes and other vegetables, breads, and cereals. Whole grain
foods, fruits, vegetables, and legumes (dried beans and peas) should be the
source of most of the carbohydrates in the diet. Mindy Hermann, M.B.A., R.D.

Q: What happens when you restrict your carbohydrate intake? What vitamins
and nutrients are lost?

A:  If you restrict carbohydrate intake severely, you can push the body into
ketosis, an abnormal metabolic state. The claim is that as a result,
calories are "lost" in the urine as a result of the incomplete metabolism of
fat. In fact, there have been no studies that adequately address the
question of how many calories are actually "lost," but experts believe that
it is too few to have a significant effect on weight. The nutrient that is
found uniquely in vegetables and fruits is vitamin C. Plant foods are also
the unique sources of fiber, and they provide an abundance of antioxidant
compounds, whose role in diet and health is under active investigation.
Jeanne Goldberg, Ph.D., R.D.

Q: Why do people lose weight on low carbohydrate diets?

A:  There are two reasons that people lose weight on low carbohydrate diets.
In the short term, with drastic dietary restriction of carbohydrate, the
body turns to stored glycogen as a source of carbohydrate. Since glycogen is
stored with water, the depletion of these stores is associated with
considerable fluid loss early in the regimen. The weight lost is regained as
soon as the individual resumes eating carbohydrate. The second reason
relates to the fact that individuals who continue to follow these diets
actually consume fewer calories than they burn, either because they
experience a loss of appetite, possibly related to the ketosis or because
they become bored with the diet and simply begin to eat smaller quantities
of food. Jeanne Goldberg, Ph.D., R.D.

Q: Why should low carbohydrate diets be avoided?

A:  The body is designed to burn, for energy, carbohydrate first and
foremost. Although the body can burn fatty acids (stored in the adipose
tissue), physiologically this is a secondary mechanism after our limited
carbohydrate stores, in the form of glycogen, have been partially expended.
The minimum amount of carbohydrate needed to ensure available glucose for
the brain to function normally is 130 g/day for adults and children.
However, most of us consume 200 to 300 g each day depending on our body
size. In addition to the minimum requirement for normal body metabolism,
many key vitamins are found in the food supply associated with carbohydrate
sources, such as vitamin C, most B vitamins, and dietary fiber, which is
helpful for gastrointestinal regulation. Ann M. Coulston, M.S., R.D.,
F.A.D.A.

Q: What are the disadvantages of diets too high in protein and fat?

A:  In addition to the fact that these diets are typically very low in
fiber, contain little if any vitamin C, and antioxidants found in plant
foods, these diets tend to be high in saturated fat. Decades of research
have demonstrated that this is a major factor in elevated serum cholesterol
and in the cardiovascular disease associated with it. Long-term consumption
of large amounts of fat has also been associated with several types of
cancers. Beyond that, these diets do not provide long-term solutions to
weight control. Jeanne Goldberg, Ph.D., R.D.

Q: What factors contribute to people becoming dehydrated when they are
dieting?

A:  The number one source of dehydration during dieting is consuming a high
protein diet. The metabolism of dietary protein generates by-products that
must be filtered out through the kidneys. This filtration is accompanied by
additional fluid necessary to dilute these waste products of protein
metabolism. Dehydration also can ensue from the breakdown of muscle tissue
that accompanies dieting. Low calorie diets, as well as weight loss diets
that are low in carbohydrates, are associated with greater loss of muscle
tissue. Mindy Hermann, M.B.A., R.D.

Q: What is the safest way to loose weight for the long term?

A:  Probably the only method of weight loss that can be considered "unsafe"
is long-term fasting (consuming nothing by mouth). However, for some people
reducing caloric intake by decreasing carbohydrate or fat in the diet may be
unhealthy. The "safest" method and the method that, theoretically, should
produce desired long-term weight loss is to decrease portion size of all
foods. This requires self-discipline, which can be extremely difficult in
many settings. For example, to decrease portion sizes, one should avoid
settings that encourage over-consumption, such as "all-you-can-eat" settings
and restaurants known to serve large portions. Ann M. Coulston, M.S., R.D.,
F.A.D.A.

Q: How should the average person evaluate the merits of a particular diet
plan before implementing?

A:  A diet plan should not exclude any one food group or particular food.
Nor should it severely limit any food with the justification that that food
is responsible for overweight. The diet plan also should not promise
dramatic weight loss. Foods to be included in a sensible weight loss plan
are grain foods (at least one per meal), fruits, vegetables, dairy products
(for calcium and protein), and protein foods like beef, poultry, fish, eggs,
and vegetable sources of protein like legumes and nuts. No single food group
should be touted as being unlimited or allowed in unusually large
quantities. Fat need not be strictly limited, except to the extent that it
contributes to total calories, and a person trying to lose weight needs to
limit total calories. Mindy Hermann, M.B.A., R.D.

Q: A friend of mine has been on a low-carbohydrate, high-protein diet. I'm
confused. Is this a healthy way to lose weight?

A: With the current popularity of diets that promote protein imbalance while
limiting carbohydrates, it's easy to become confused and wonder if these
weight loss claims are really valid. Many high-protein, low carbohydrate
dieters will lose weight in the short-term, mainly because these diets
restrict calories.

The basic premise of high-protein, low-carbohydrate diets is to avoid or
limit carbohydrates, while loading up on protein and fat. Many of these fad
diets recommend avoiding rice and pasta, as well as vegetables such as
potatoes, carrots, peas, corn and squash and fruits, such as bananas, apples
and raisins.

Diets that severely limit carbohydrates have possible side effects,
including dehydration, nausea and fatigue. These diets also tend to be low
in nutrients such as vitamin C and can accelerate calcium loss from your
body. In the long-term, when carbohydrates are restricted, the accompanying
lack of dietary fiber can lead to serious health risks such as
diverticulitis, inflammation of the colon and increased risk of cancer. The
American College of Sports Medicine, the American Dietetic Association, the
Women's Sports Foundation and the Cooper Institute for Aerobics Research
issued a joint statement that high-protein, low-carbohydrate diets are not
the answer for weight loss.