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Transcript
WLG 126
L
ow-carb Diets: Could They Possibly Be That Good?
Guen Brown, Extension Specialist, Nutrition and Health
Jason Nguyen, M.S./R.D. candidate, West Virginia University
Low-carbohydrate diets, like the Atkins Diet, have been around for a long time.
Do they work? Are they safe? The list below shows some of the more well-known
low-calorie diets. The different types do have minor variations, but all are basically
low-carb diets.
• Atkins Diet, probably the most famous one, by Dr. Robert Atkins
• High-protein Diet
• Stillman Diet
• Scarsdale Diet
• Hollywood Diet
• Ketogenic Diet
• Zone Diet
• South Beach Diet
What Are Low-carb Diets?
Low-carb diets are based on the premise that a diet very low in carbohydrate
leads to a reduction in the body’s insulin production, resulting in fat and protein
(muscle) stores being used as the main energy source. However, the recommended
carbohydrate intake varies among diets. Some low-carb diets restrict carbohydrate
intake to less than 20 percent of total calories; others permit up to 40 percent.
To complicate matters further, many low-carb diets are divided into “phases.”
Phase 1 typically permits only minimum amounts of carbs; Phases 2 and 3
are usually more generous. Compare this with the U.S. Department of
Agriculture (USDA) recommendation to eat about 50 percent to 55 percent
of calories from carbohydrates.
The fat intake recommendations vary too. Some low-carb diets suggest eating
55 percent to 65 percent of one’s calories from fat. USDA recommends eating
not more than 30 percent of calories from fat. What is even more controversial,
is that some low-carb diets actually state that animal fats may be eaten liberally
along with vegetable oils. This advice contradicts the recommendations of most
heart specialists.
The aim of low-carbohydrate diets is to force the body to use fat as its main
energy source, since no carbohydrates are available. When fat is being used to
provide fuel for your body, the liver produces ketone bodies to provide energy
for parts of the body that cannot use fat as an energy source, particularly the brain
and red blood cells. If ketone bodies are made faster than they are used, they build
up in the blood and cause a condition known as ketosis. Ketosis can cause your
body’s organs to fail and result in gout, kidney stones, kidney failure, nausea, loss
of appetite, and bad breath. If this keeps up, your body’s blood becomes too acidic.
This is called ketoacidosis and can lead to brain damage and eventually death.
Suggested protein intake in low-carb diets ranges from 25 percent to 40 percent.
The USDA recommends you get between 15 percent and 20 percent of calories
from protein. Since fat and protein are generally found in the same foods, a diet
high in fat is usually high in protein.
– continued –
These foods are restricted in
a low-carb diet.
What Are
Carbohydrates?
Carbohydrates or “carbs” are
the main source of energy for
the body. Grains, fruits, legumes
(beans, peas, and lentils), dairy
products, and vegetables contain
carbohydrates. The two main
types of carbs in food are simple
carbohydrates (sugars) and
complex carbohydrates (starches
and higher-fiber foods).
These foods are often restricted in a low-carb diet.
Simple carbohydrates are found in
soda pop, candy, pastries, and other
sweets. They provide energy that is
5 grams. The amount of carbohydrates needed depends
quickly used by the body before it uses protein and fat,
upon a person’s total calorie needs. However, eating a diet
the other energy sources from food. Unfortunately, foods
containing generous amounts of fruits, vegetables, grains,
with high amounts of simple carbohydrates do not usually
and cereals is an excellent practice for both adults and
contain any important vitamins or minerals. This means
children. The Food and Nutrition Board of the National
that they provide empty calories.
Academy of Sciences has reported that the absolute
Complex carbohydrates are chains of sugars. Legumes,
minimum amount of carbohydrates the body needs per
potatoes, yams, and grains such as wheat, rice, corn,
day is 50 to 100 grams (Dietary Reference Intake Table,
and oats are complex carbohydrates in the form of starch.
USDA Food and Nutrition Board, June 2004).
While all plant foods contain fiber, our body does not
digest fiber, and no calories are produced. Starches take
longer to be digested than simple sugars. Eating starchcontaining foods makes our body feel full, and energy
is provided more slowly.
Your body converts or breaks down most carbohydrates
into glucose. Glucose is circulated through the body
in blood and provides energy. The primary fuel used
by the brain is glucose. Some glucose can also be stored
in the muscles and used for exercise, helping your body
function properly without tiring easily.
How Much Carbohydrate Should I Eat?
A normal starch, fruit, or sweet food serving contains
about 15 grams of carbs. One serving of dairy food has
about 12 grams, and a vegetable serving consists of only
Do Low-carbohydrate Diets Work?
In the short term, most people who go on low-carb diets
do lose weight, and they lose it very quickly. However,
the majority of weight loss comes from loss of water and
muscle tissue, not fat, which is what you need to lose to
keep the weight off. Also, if you’re trying to lose weight
permanently, losing precious lean muscle tissue is like
sabotaging your own body. Muscle tissue burns calories
even when you are at rest. A decrease in the amount of
muscle tissue you have will lead to a decrease in the
number of calories you need each day to maintain your
weight, making it much harder to keep your weight under
control when you stop following the low-carb diet.
High-protein, low-carbohydrate diets seem to work,
at least in the beginning. Dieters experience an initial
weight loss, but it is rarely permanent. The weight
reduction is a result of lost water and body fluids.
Energy (glucose) stores are depleted, which can lead
to fatigue, weakness, nausea, constipation, and
dehydration. Later, the decrease in weight comes from
loss of fat and muscle tissue. This may affect vital body
organs. Weight is usually regained quickly if the diet
is stopped.
What’s Involved?
Eating a well-balanced meal is better.
Basically you cut out virtually all carbohydrate from
your diet and increase your protein and fat intake. So you
cut out things like pasta, bread, rice, and alcohol, but you
eat unlimited amounts of meat, cheese, and butter. That’s
why the Atkins Diet claims are so appealing.
Are There Other Things I Need to Know
About Low-carb Dieting?
The low-carb diet craze has led to an explosion of new
food products and advertisements in grocery stores and
restaurants. While many food items are essentially new,
the concept of low-carb foods is not “revolutionary.”
Neither is it a breakthrough in weight management.
Rather, the idea originated in the 1950s and has been in
and out of style every few years for the past five decades.
More recently, the Atkins Nutritional Approach, South
Beach Diet, Zone Diet, and several other high-protein,
low-carb diets have gained popularity. They are similar
in that they encourage eating lean meats, eggs, cheeses,
nuts, and oils while restricting grains (bread, rice, cereal,
pasta), fruits, some dairy foods, and vegetables. Because
people tend not to stay on the diets for long periods, little
research has been done on the long-term health
effects of following this eating pattern. However,
when grains, some dairy products, and fruits
and vegetables are restricted in the diet, many
essential nutrients are not available in recommended
amounts. Also, no legal definitions exist for “low
carb.” An official way of figuring them out has
not yet been established by the Food and Drug
Administration (FDA).
To cater to high-protein, low-carb dieters, food
products are being introduced with “low net carbs”
by substituting sugar alcohols for sugar or by
increasing the fiber content. Eating excessive
amounts of sugar alcohols can have a
laxative effect.
A high-fiber diet has been linked with a lower risk
of heart disease, diabetes, and possibly colon cancer.
However, a sudden increase in fiber intake can
cause increased intestinal gas and bloating. Increasing
fiber intake should be done gradually over several weeks,
accompanied by drinking lots of fluids to prevent
digestion complications.
The animal foods and products in these fad diets can
be high in cholesterol and saturated fat, which leads to
heart problems. Avoiding healthy foods and food groups
altogether will lead to malnutrition, diseases, and some
cancers. Ignoring or strictly limiting fruits and vegetables
is not recommended. These foods contain cancer-fighting
vitamins, or antioxidants, and have other health benefits.
Is a Low-carb Diet Healthy?
In a word, no! Essential vitamins and nutrients come from
a balanced diet, and low-carbohydrate diets certainly are
not balanced. You can get many essential nutrients from
fruit, vegetables, and grains. Low-carb diets allow only
very small amounts of fruit and vegetables – definitely not
enough to provide your recommended daily allowance.
The Atkins Diet claims to clear up all manner of ailments,
but the bottom line is that these diets are lacking in
nutrients essential for good health. Also, the high level
of protein puts a huge strain on your kidneys. Low-carb
diets are also likely to encourage yo-yo dieting – cycles
of losing and regaining weight – which has been shown
to be a health risk.
So Why Do It?
People are often attracted to low-carb diets because
weight loss is very rapid, and we like to see instant results
on the scales! Many times, people in the entertainment
world go on low-carb diets because they want to lose
weight quickly. They don’t do it for permanent weight
loss or good health. Others may not understand the
possible long-term effects of diets that are not based
on a variety of foods.
Is There a Take-home Message?
Diets that recommend cutting back on carbohydrate
foods are an “in vogue” means of losing weight. They
have gained a lot of media attention. However, these
diets could actually harm health in the longer term. The
American Heart Association has expressed concern that
their high-fat content, particularly saturated fat, increases
the risk of heart disease in those who follow these diets
long term. Low-carbohydrate diets go against all the
current recommended healthy eating principles and are
deficient in many vitamins, minerals, and dietary fiber
since they restrict the intake of fruit and vegetables. There
are also concerns that these diets, if followed long term,
may increase the risk of kidney, bone, and liver problems.
Combining a balanced, healthy diet with exercise is still
the most effective and safe long-term way to lose weight.
However, the results are gradual and require perseverance.
Quick fixes such as low-carb diets do not hold up to
scrutiny. There are no long-term studies on the safety
or efficacy of these diets.
Perhaps the greatest risk of the low-carb diet trend is
the impact it may have on eating behaviors of individuals
who haven’t established sensible eating habits. Weight
management incorporates a balanced lifestyle of a healthy
diet and regular physical activity. In order to lose weight,
you must eat fewer calories than you use. Decreasing
portion sizes and keeping a diary of the foods you eat
can lead to long-term health. Low-carbohydrate diets
are not recognized as healthy diets. Making small
changes, such as decreasing portion sizes and
increasing physical activity, are healthy ways
to lose weight.
References
USDA Food and Nutrition Board, June 2004
Institute of Medicine of the National Academies,
August 2004
American Heart Association Statistical Fact Sheet,
Nutrition and Heart Disease, May 2004
2005: 1M
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