A carbohydrate is a member of a large class of natural organic substances. Carbohydrates are in almost everything we eat, sometimes in very small amounts but often times in substantial quantities. Some examples of common carbohydrates are sugars, starch and cellulose. Carbohydrates are important because they provide a storage of energy in our bodies that is quickly accessible. In fact, carbohydrates make up the major source of dietary energy for people all over the world (Stephen 1995). In addition, carbohydrate intake increases levels of a substance called tryptophan in the body, which releases serotonin in the brain. Whether this phenomenon affects our hunger and eating habits is still unclear (Fairburn 1993).
Almost all of the information that you'll find on the world wide web
about the subject of low-carb diets is basically the same. There are thousands
of documents, so rather than reading each one of them just look at this
brief summary of the information that is out there. Following the web summary
is a literature summary of the information contained in published professional
and scientific journals about the topic of low-carb diets.
Low-carbohydrate diets are essentially very simple. The idea is that by restricting daily carbohydrate intake, cravings for carbohydrates will eventually subside, resulting in a lower amount of food consumption and weight loss. Low-carb diets are meant to be used as general weight loss plans, especially for people who are considered "Carbohydrate Addicts". These addicts have consistent and uncontrollable cravings for carbohydrates, resulting in carbohydrate binges (http://www.dietician.com/faddiet.ntml). The majority of low-carb diets are based on the assumption that "obesity and most of its related problems are often (maybe even usually) caused by an insulin problem, not chronic overeating, fat consumption, or refined sugars per se" (http://www.syndicomm.com/lowcarb.html). Therefore, a low-carb diet seeks to curb carbohydrate cravings by lowering overall carbohydrate intake. The philosophy of low-carb diets is that when the cravings have subsided, not only will carbohydrate intake be substantially lower, but food intake in general will decline, resulting in weight loss. There are many low-carb diet plans that are available. Some of the most popular include:
** "Entering The Zone", by Dr. Sears
** Dr. Atkins low-carbohydrate diet
** Dr. Richard Heller and Dr. Rachel Heller's "Healthy For Life"
and "The Carbohydrate Addict's Diet"
**Dr. Michael Eades and Dr. Mary Eades "Protein Power"
The web contains countless testimonials from people who have successfully tried low-carb diets. They maintain that they no longer crave cookies and junk, nor do they have carbohydrate binges any longer. The dieters report that once their cravings for carbohydrates had ended, they also experienced a decline in uncontrollable cravings for any particular foods. Significant weight loss is reported, especially for people that remain on the diet for an extended length of time. Besides personal accounts given by dieters, the web also contains several documents published by specialists from health centers. These papers support the fact that a low-carbohydrate diet will result in weight loss. However, although the dieter will probably lose some weight, the changes are "entirely due to changes in water balance. No other differences in body composition or weight loss are observed" (http://www.med.Stanford.edu/school/DGIM/Teaching/Modules/obesity.html#RTFToC7). Therefore, these diets would not be suitable for long term weight loss because once the dieter resumes their normal eating habits the weight will return very quickly.
The most reported negative side effect associated with low-carb diets is the "unhealthy metabolic mode called ketosis" (http://homearts.com/depts/health/049afl.htm). Although it is also associated with many other conditions such as diabetes, ketosis can be caused by a deficiency of carbohydrates in the body. Ketosis is a metabolic disorder, characterized by a build up of chemicals known as ketones, which are produced by the body as a by-product of combusting fat (Leung 1995). An increase in the level of ketones in the body results in larger than normal excretion of sodium and water loss. These symptoms produce most of the weight loss that is reported by low-carb dieters. During ketosis, many people tend to feel sluggish and tired and will experience low levels of energy. Other, less severe side effects include constipation, gas, and excess protein in the body
Contrary to the advertising and personal accounts found on the web about
low-carb diets, reports in scientific literature are based on well-researched
theories and studies done specifically on the topic. The conclusions are
somewhat similar to those made in the personal accounts on the web. The
major difference is that the scientific literature explores the issue of
long-term effects, the health consequences of a low-carb diet and the element
of uncertainty that still surrounds that concept of low-carbohydrate intake.
According to the experts, diets that are low in carbohydrates do indeed
result in weight loss. In laboratory studies, greater weight loss is observed
when subjects follow low-carb diets than when they are following low fat
diets. But, is simple weight loss the only answer that dieters are looking
for? What about a healthy body, a body in good shape, that is fit and toned?
The low-carb diet alone, like all diets, does nothing to change body composition
(Racette 1995). In order to achieve and maintain healthy weight loss, a
sensible diet plan should include not only a meal chart but also an exercise
regimen. All of the experts agree that there is no optimum diet or plan
to achieve weight loss (Peterson 1995). Rather, lifestyle changes must
occur that will include changes in eating habits and an increase in activity
level. By following a plan of moderation with these elements, that may
include a diet that is lower in carbohydrate intake than average, anyone
can become a more healthy person.
As mentioned earlier, when going on a strict low-carb diet, dieters
are taking a high risk of developing the metabolic disorder known as ketosis.
Ketosis will leave the dieter feeling lethargic, sluggish and tired. These
conditions can detrimental to an effective diet because they will result
in decreases activity levels. However, it has been found when carbohydrates
were restored to the body, the ketosis diminished, leaving no ill effects
in the long term. But it was at this time, without any other intervention
going on, that the dieter began to regain all the weight that he or she
had lost. So, the negative health consequences disappear but so does the
positive weight loss (Wing 1995).
Several studies have been done to determine whether low-carb diets,
or ketogenic states, have any negative affects on cognitive functioning.
One such study, by R.Wing at the University of Pittsburgh School of Medicine,
evaluated the attention and mental flexibility of subjects on this type
of diet. Although the researchers found that the diet did not affect performance
on these types of tasks, they did discover that the ketosis state adversely
affected test performance that required "higher order mental processing
and flexibility" (Wing 1995). They concluded that further research
was needed to confirm this information, and to explore the effect of low-carb
diets and ketogenic states on other areas of mental functioning.
A strict diet, low in carbohydrates, will in fact result in weight loss.
However, this weight loss may also present with it an unhealthy metabolic
disorder known as ketosis. Some of the adverse effects of ketosis are still
under investigation, but researchers are certain that the condition negatively
affects energy levels and cognitive performance in certain areas. In order
to maximize the effects of any weight loss plan, the plan needs to be done
in moderation, so that it can be incorporated into the dieter's life as
a lifestyle change rather than a temporary situation. Therefore, a diet
that is simply lower in carbohydrates combined with an exercise regimen
that is realistic, would be the optimal plan for achievement and maintenance
of weight loss and a healthy life style.
Fairburn, Christopher G. and Wilson, G. Terence. Binge Eating. The Guilford Press, New York, 1993.
Leung, L.H. "Pantothenic acid as a weight reducing agent: fasting without hunger, weakness and ketosis" Medical Hypotheses. 44(5):403-5 May, 1995.
Peterson, C.M., and L. Jovanic-Peterson. "Randomized crossover study of 40% vs. 55% carbohydrate weight loss strategies in women" Journal of the American College of Nutrition. 14(4):369-75, Aug, 1995.
Racette, S., et all. "Effects of aerobic exercise and dietary carbohydrate on energy expenditure and body composition during weight reduction in obese women". American Journal of Clinical Nutrition. 61(3):486-94, March 1995.
Stephen, A.M., G.Seiber, Y.Gerster, and D.Morgan. "Intake of carbohydrate and its components-- international comparisons, trends over time, and effects of changing to low-fat diets". American Journal of Clinical Nutrition. 62(4):851S-867S, Oct. 1995.
Wing, R.R., J.Vazquez and C.Ryan. "Cognitive effects of ketogenic
weight reducing diets" International Journal of Obesity & Related
Metabolic Disorders. 19(11):811-6, Nov 1995.
Psychology DepartmentThe Health Psychology Home Page is produced and maintained by David Schlundt, PhD.
Vanderbilt Homepage | Introduction to Vanderbilt | Admissions | Colleges & Schools | Research Centers | News & Media Information | People at Vanderbilt | Libraries | Administrative Departments | Medical
|Return to the Health Psychology Home Page|
|Send E-mail comments or questions to Dr. Schlundt|