Description
At any given time, about one-third of Americans
are trying to lose weight. Many of them succeed in the
short term, but the number of people who can keep the
weight off for more than a year is small (around 25%),
and the number that make the lifestyle changes neces-
sary to keep weight off for five or more years even
smaller (less than 10%). The constant cultural pressure
to be thin, both for social and health reasons, leads to a
cycle of dieting and weight loss followed by weight gain,
and then more dieting. The changes in weight can be as
small as 5 lb (2.3 kg) or as great as 50 lb (23 kg).
Researchers generally place weight cyclers into
one of three categories.
Severe weight cyclers have lost 20 lb (9 kg) or more
three or more times.
Moderate weight cyclers have lost 10–20 lb (4.5–9
kg)three or more times.
Mild weight cyclers have lost 5–10 lb (2.3–9 kg) three
or more times.
Demographics
More women than men are weight cyclers, just as
more women than men go on diets. Weight cyclers can
be of any race, ethnicity, or age. Researcher are find-
ing that weight cycling is beginning at an earlier and
earlier age, probably because of the increase inchild-
hood obesity.
Most weight cyclers are overweight, defined as a
body mass index(BMI) of 25.0–29.9, obese, defined as
a BMI of 30–39.9, or morbidly obese, with a BMI of 40
or above. The majority of studies are done on people
who are overweight or obese.
Adolescent girls of normal weight may also
become weight cyclers because of cultural pressures
to be thin and/or because they have a distortedbody
image. Actors, who may need to bulk up or slim down
for a role, and athletes, who often gain weight in the
off season and lose it during pre-season training are
other examples of normal-weight people who may be
weight cyclers. Much less research is done on normal-
weight people who weight cycle than on overweight
and obese people who weight cycle. Most research on
normal-weight yo-yo dieters is done on adolescent
girls. Many studies have found that binge-eating,
where an individual uncontrollably eats abnormally
large amounts of food at one sitting, is fairly common
among weight cyclers.Causes and symptomsWeight cycling is not a disease, but is a sign of
repeated attempts and failures to maintain weight. Its
cause is simple—a period of during which the individ-
ual takes in fewer calories than she uses that results in
weight loss followed by a period when the individual
eats more calories than she uses that results in a weight
gain. However, understanding why weight cycling
occurs and determining if these changing periods of
calorie intake affect both future weight loss and health
is complex.
In the 1980s,obesityresearchers began asking
whether these failed attempts at permanent weight
loss affect the indivual’s health or ability to lose weight
in the future. Weight and weight cycling are difficult
topics to research in humans because so many differ-
ent physical and emotional factors affect the process
of weight gain and loss. These include:
genetics. Twin and family studies have shown that there
is an inherited component to weight, just as there is to
height. As scientists have become more adept at isolat-
ing individual genes, they have found close to 300 genes
that may play a role in determining weight. Although
inheritance is not necessarily destiny—plenty of thin
people have obese parents and siblings—genetic
influences do help explain why some people gain
weight more easily than others and have more diffi-
culty keeping off the weight they lose.
hormones. Ghrelin is a hormone produced in the
stomach that stimulates appetite. It increases before
meals and decreases after meals. Leptin is a hormone
produced by fat cells (adipose tissue) that has the
opposite effect. It tells the brain that enough food
has been consumed and that the individual should
stop eating. Differences in the levels of these hor-
mones or in the body’s responsiveness to them appears
to play a role in losing and regaining weight.
emotional factors. Some people feel sick and cannot
eat when they are stressed or upset. Many others turn
to food for comfort. Other people eat when they are
angry rather than addressing the situation that is
causing the anger. Often people are able to maintainKEY TERMS
Morbidly obese—Defines person who is 100 lb (45
kg) or more than 50% overweight and has a body
mass index above 40.
Type 2 diabetes—Sometime called adult-onset dia-
betes, this disease prevents the body from properly
using glucose (sugar).Weight cycling