Weight loss, in the context of medicine or health or physical fitness, is a reduction of the total body weight, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon and other connective tissue. It can occur unintentionally due to an underlying disease or can arise from a conscious effort to improve an overweight or obese state.
Unintentional weight loss
Poor management of type 1 diabetes mellitus, also known as insulin-dependent
diabetes mellitus (IDDM), leads to an excessive amount of glucose and an
insufficient amount of insulin in the bloodstream. This triggers the release of
triglycerides from adipose (fat) tissue and catabolism (breakdown) of amino
acids in muscle tissue. This results in a loss of both fat and lean mass,
leading to a significant reduction in total body weight. Note that untreated
type 1 diabetes mellitus will usually not produce weight loss, as these patients
get acutely ill before they would have had time to lose weight.
Myriad additional scientific considerations are applicable to weight loss:
physiological and exercise sciences, nutrition science, behavioral sciences, and
other sciences.
One area involves the science of bioenergetics including biochemical and
physiological energy production and utilization systems, that is frequently
evidence of diabetes, and ketone bodies, acetone particles occurring in body
fluids and tissues involved in acidosis, also known as ketosis, somewhat common
in severe diabetes.
In addition to weight loss due to a reduction in fat and lean mass, illnesses
such as diabetes, certain medications, lack of fluid intake and other factors
can trigger fluid loss. And fluid loss in addition to a reduction in fat and
lean mass exacerbates the risk for cachexia.
Infections such as HIV may alter metabolism, leading to weight loss.[1]
Hormonal disruptions, such as an overactive thyroid (hyperthyroidism), may also
exhibit as weight loss.[2]
Recent research has shown fidgeting to result in significant weight loss. [3]
Intentional weight loss
Intentional weight loss refers to the loss of total body mass in an effort to
improve fitness, health, and/or appearance.
Therapeutic weight loss, in individuals who are overweight or obese, can
decrease the likelihood of developing diseases such as diabetes,[4] heart
disease, high blood pressure, stroke, osteoarthritis,[5] and certain types of
cancer.
Weight loss occurs when an individual is in a state of negative energy balance.
When the body is consuming more energy (i.e. in work and heat) than it is
gaining (i.e. from food or other nutritional supplements), it will use stored
reserves from fat or muscle, gradually leading to weight loss.
It is not uncommon for some people who are currently at their ideal body weight
to seek additional weight loss [6] in order to improve athletic performance,
and/or meet required weight classification for participation in a sport.
However, others may be driven by achieving a more attractive body image [7].
Consequently, being underweight is associated with health risks such as
difficulty fighting off infection, osteoporosis, decreased muscle strength,
trouble regulating body temperature and even increased risk of death.[8]
Therapeutic weight loss techniques
The least intrusive weight loss methods, and those most often recommended by
physicians, are adjustments to eating patterns and increased physical activity,
generally in the form of exercise. Physicians will usually recommend that their
overweight patients combine a reduction of processed[9] and caloric content of
the diet with an increase in physical activity.[10]
Other methods of losing weight include use of drugs and supplements that
decrease appetite, block fat absorption, or reduce stomach volume. Medicines
with herbs such as Fucus vesiculosus are popular.[11] Finally, surgery (i.e.
bariatric surgery) may be used in more severe cases to artificially reduce the
size of the stomach, thus limiting the intake of food energy.
Crash dieting
A crash diet refers to willful nutritional restriction (except water) for more
than 12 hours. The desired result is to have the body burn fat for energy with
the goal of losing a significant amount of weight in a short time. Crash dieting
is not the same as intermittent fasting, in which the individual periodically
abstains from food (e.g., every other day).
Weight loss industry
There is a substantial market for products which promise to make weight loss
easier, quicker, cheaper, more reliable, or less painful. These include books,
CDs, cremes, lotions, pills, rings and earrings, body wraps, body belts and
other materials, not to mention fitness centers, personal coaches, weight loss
groups, and food products and supplements. US residents in 1992 spent an
estimated $30 billion a year on all types of diet programs and products,
including diet foods and drinks.[12]
Between $33 billion and $55 billion is spent annually on weight loss products
and services, including medical procedures and pharmaceuticals, with weight loss
centers garnering between 6 percent and 12 percent of total annual expenditure.
About 70 percent of Americans' dieting attempts are of a self-help nature.
Although often short-lived, these diet fads are a positive trend for this sector
as Americans ultimately turn to professionals to help them meet their weight
loss goals.[13]