Dieting
Dieting is the practice
or habit of eating (and drinking) in a regulated fashion, usually
with the aim of losing weight. It is also used in some cases to
gain weight or to regulate the amounts of certain nutrients entering
the body.
History of Dieting
The practice of dieting in order to lose weight is
ancient in its origins. Throughout the 17th and 18th centuries,
physicians and patients regulated their food carefully, in order
to prevent disease. The scientific classification of foods was broken
down into proteins, carbohydrates, starches and lipids. Doctors
and scientists began experimenting with targeted diets in the 19th
century.
William Banting is one of the first people known to have successfully
lost weight by dieting, circa 1863, by targeting carbohydrates.
(The low carbohydrate diet, marketed today as the Atkins Diet,
remains popular today.)
What dieting is not
Certain religions, such as Judaism
and Islam, impose strict restrictions on food choices and preparation.
These restrictions, however, are not usually considered "dieting."
Vegetarianism is usually not considered
"dieting," as it is most often adopted for religious,
spiritual or ethical reasons, or in some cases because other food
choices are not available.
Anorexia nervosa and bulimia,
which are psychological and neurological disorders that cause
victims to endanger their lives with calorie restriction, must
not be confused with dieting.
Dieting techniques
Most typically, "dieting" means
eating in a carefully planned way in an attempt to reduce excess
body fat and decrease bodily measurements, such as clothing size.
There exist a (sometimes confusing) multitude
of weight loss techniques, many of which are ineffective. What
works for one person will not necessarily work for another, due
to metabolic differences and lifestyle factors.
Scientific principles surrounding dieting
Successful weight loss diet is all about energy in versus energy
out. If a person takes in less food energy than he or she expends
over a period of time, the person may burn fat and subsequently
lose weight.
Diets affect the energy in component of the energy
balance by limiting or altering the distribution of foods. Techniques
that affect the appetite can limit energy intake by affecting
the desire to overeat. This can be attempted by focusing on foods
that are filling, through the use of certain appetite-suppressing
drugs, or through activities such as mild exercise, that affect
appetite. Other techniques address habitual or emotional eating.
Affecting the energy out component is the focus
of fitness and exercise programs. These might also be included
in a comprehensive "diet."
Dieting in order to lose weight does just that
-- you lose weight, water, some fat and muscles. Since muscles
are denser, you lose a lot of weight, but little in size. Fat
is bulkier, so a three pound fat loss can cause a size loss.
To lose a pound of fat, one must create a caloric
deficit of approximately 3,500 calories (37,600 kJ per kilogram
of fat); therefore, if a person creates a deficit of 500 calories
per day, the person will lose approximately 1 pound of fat per
week (5,400 kJ per day to lose a kilogram a week).
Muscle-loss during weight-loss can be restricted
by regularly lifting weights and by a high protein intake. (It
is said that 0.8 to 1.0 g of protein per pound of body weight
(1.76 to 2.20 g/kg) per day is sufficient.)
Weight loss groups
There exist both profit-oriented and non-profit weight loss organizations
who assist people in their weight loss efforts. (Examples of the
former include Weight Watchers and Jenny Craig; examples of the
latter include Overeaters Anonymous and a multitude of non-branded
support groups run by local churches, hospitals, or like-minded
individuals.) These organizations' customs and practices differ
widely, but most all of them leverage the power of group meetings
with regards to counseling, emotional support, problem-solving,
and the passing along of useful information. Some advocate certain
prepared food or special menus, while others train how to make healthy
choices from menus and while grocery-shopping.
Fad diets
Many 'fad' diets become widely popular for a short
period of time, only to fade out. Although some fade from popularity
due to being ineffective, some merely lose the public's interest.
Judging their nutritional merit can be especially difficult given
that most diet proponents locate medical professionals to back up
their work. Examples of such fads include the grapefruit diet, low-fat
diets, and Atkins.
Most fad diets emphasize a technique for accelerating natural
fat loss over the basic nutritional idea of energy balance, or
ignore it completely. The energy you take in (in the form of calories
in food, whether fat, protein, or carbohydrate) must be less than
the energy you burn in order to lose weight, so that your body
burns fat to make up the energy deficit. If you take in more energy
than you burn, your body will tend to store this excess energy
as fat.
Grapefruit diet
On the grapefruit diet, the consumption of grapefruit with each
meal was said to increase the metabolic rate, burning fat and
enabling rapid weight loss. The grapefruit diet was eventually
found to be entirely ineffective.
Low-fat diets
Low-fat diets were popular during the '80s and '90s, encouraging
people to eat foods low in fat (or without fat altogether) and
instead eat foods high in carbohydrates. The diet worked on the
principle that of the three main macro-nutrients (fat, carbohydrates
and protein), only fat was the one which would cause weight-gain.
This failed as people ended up eating excessive amounts of low-fat
foods rich in refined carbohydrates and sugar, and so did not
lose much weight, or even gained it due to the energy from the
carbohydrates.
Atkins
Atkins encourages controlling carbohydrate intake, and encouraged
meats, nuts, unsweetened fruits, berries and green vegetables.
This causes rapid weight loss for many people, although it continues
to be disputed whether this is due to a metabolic advantage of
ketosis, as Atkins claimed. Some of the initial rapid weight loss
is due to depletion of glycogen stores in the liver. Glycogen
must be associated with several times its weight of water in the
body. Low carbohydrate diets have been shown to reduced the fasting
levels of triglycerides. Elevated triglycerides are a demonstrated
risk factor for heart disease and also account for part of the
risk of low density cholesterol due to their associated worse
particle size profile. Any successful diet for losing weight will
cause some ketosis, since ketones are produced when the body is
using fat energy to synthesize glucose (gluconeogenesis) during
the long overnight fast (sleep). Elevated levels of fasting triglycerides
(TGs) are the product of de novo lipogenesis (synthesis of new
fats) from glucose substrate. If the liver was engaged in gluconeogenesis
from fat, and synthesizing fat from glucose at the same time,
this would be a futile cycle, and a fantastic way to waste energy
and lose weight. For most of human history, it has been important
to survival to avoid such inefficiency, so the body switches modes
to avoid this futile cycle. This explains the dramatic reductions
in fasting TGs seen in many low carbohydrate dieters.
Medical diets
Medical conditions often require the use of a special diet that
either contains or lacks certain chemicals. For example, a person
who has diabetes is often on a diet designed to carefully regulate
their blood sugar level, sufferers of celiac disease must follow
a gluten-free diet, the lactose-intolerant omit milk and dairy products,
and people with kidney disease must follow a strict low-sodium diet
to ease the strain on their kidneys.
Treatment for mild hypertension includes a diet
rich in fruits, vegetables, and fat-free dairy foods, and low
in fat and sodium, to lower blood pressure.
Very Low Calorie Diets
The Very Low Calorie Diet, or VLCD, is a special diet to be undertaken
with medical supervision. It offers rapid fat loss over a short
timeframe, but can be dangerous for some people. It consists of
the consumption of a special powder mixed in with 200-300 ml of
water to be taken three times a day. The drink, similar to a milkshake,
provides approximately 1914 kJ (456 Cal) of energy per day when
consumed at breakfast, lunch and dinner. It contains all necessary
vitamins and minerals, although there is a risk of overdosing on
selenium if a person consumes more than they should (more than three
times per day). VLCDs should only be used for dieting when a person's
body mass index exceeds 30. In addition, at least two liters of
water must be consumed per day and a person should consider using
fiber supplements regularly. Without this, the person risks severe
constipation.
VLCDs can be very successful, but only
when used over a six- to 12-week period. Because the body is essentially
starving, it is burning up its fat stores and lowering its metabolic
rate. As soon as the diet ceases and normal food is consumed again,
there is an immediate increase in weight. Short-term use of VLCDs
(one to four weeks) will have little, if any, benefit for the
dieter, as the increase in weight will negate the weight lost
in the first place. Once the full course of the diet is finished,
it is up to the successful dieter to maintain their current weight,
via exercise and sensible eating, otherwise they will put on weight
again. VLCDs put a great deal of strain on a person's body, and
should only be undertaken with medical consultation.
Potentially hazardous dieting techniques
Yo-yo dieting is particularly dangerous and ineffective, because
it decreases the metabolism, leading to an immediate weight gain
once the caloric restrictions are eased.
Many over-the-counter (OTC) and prescribed medications
have been proven to be extremely hazardous to the health and consequently
withdrawn from sale, so consumers need to be wary.
While anyone can lose weight by fasting (temporarily
stopping one's food intake altogether), it is an extremely dangerous
practice. When concentration camp survivors, who involuntarily
suffered famine as a result of the horrendous living conditions,
were examined by doctors, what little weight they had was mostly
fat, with practically no muscle.
The only "safe" method of weight loss
is to eat a sensible healthy diet with a moderately decreased
caloric intake from your normal diet, and to increase exercise
gradually until weight loss results. It should be noted that people
may follow these guidelines and not actually lose weight, but
may see health improvements.
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