Dieting can be defined as the practice of eating food in a
controlled, regulated fashion in order to achieve or control a
person's body weight or size. Normally dieting is used, sometimes in
a combination with physical exercise, to lose weight in those who
are overweight or obese. Some people, athletes in particular follow
a diet to gain weight, usually in the form of muscle. Diets are also
important to maintain a stable body weight and size.
Weight loss diets can be generally divided into four categories: low-fat,
low-carbohydrate, low-calorie, and very low calorie. A meta-analysis of six
randomized controlled trials found no difference between the main diet types
(low calorie, low carbohydrate, and low fat), with a 4–7 pound weight loss in
all studies. At two years, all calorie-reduced diet types cause equal weight
loss irrespective of the macronutrients emphasized.
Types of Diets
Low-fat diets involve the reduction of the percentage of fat in one's diet.
Calorie consumption is reduced because less fat is consumed. Diets of this type
include NCEP Step I and II. A meta-analysis of 16 trials of 2–12 months'
duration found that low-fat diets (without intentional restriction of caloric
intake) resulted in average weight loss of 7.1 lb over habitual eating.
Low carbohydrate diets such as Atkins and Protein Power are relatively high
in protein. Low-carbohydrate diets are sometimes ketogenic (i.e. they restrict
carbohydrate intake sufficiently to cause ketosis).
Low-calorie diets usually produce an energy deficit of 500–1,000 calories per
day, which can result in a 1 lb to 3 lb weight loss per week. Amongst some of
the most commonly used low-calorie diets include DASH diet, Diet to Go, and
Weight Watchers. The National Institutes of Health reviewed 34 randomized
controlled trials to determine the effectiveness of low-calorie diets. They
found that these diets lowered total body mass by 8% in the short term, over
Very low-calorie diets
Very low calorie diets provide 200–800 calories per day, maintaining protein
intake but limiting calories from both fat and carbohydrates. They subject the
body to starvation and produce an average weekly weight loss of 3.3–5.5
lb. "2-4-6-8", a popular diet of this variety, follows a four-day cycle in which
only 200 calories are consumed the first day, 400 the second day, 600 the third
day, 800 the fourth day, and then the cycle repeats. These diets are not
recommended for general use as they are associated with adverse side effects
such as loss of lean muscle mass, increased risks of gout, and electrolyte
imbalances. People attempting these diets must be monitored closely by a
physician to prevent complications
Fat loss v. muscle loss
Weight loss typically involves the loss of fat, water and muscle. Overweight
people, or people suffering from obesity, typically aim to reduce the percentage
of body fat. Additionally, as muscle tissue is denser than fat, fat loss results
in increased loss of body volume compared with muscle loss. Reducing even 10%
body fat can therefore have a dramatic effect on a person's body shape. To
determine the proportion of weight loss that is due to decreased fat tissue,
various methods of measuring body fat percentage have been developed.
Muscle loss during weight loss can be restricted by regularly lifting weights
(or doing push-ups and other strength-oriented calisthenics) and by maintaining
sufficient protein intake. Those on low-carbohydrate diets, and those doing
particularly strenuous exercise, may wish to increase their protein intake.
According to the National Academy of Sciences, the Dietary Reference Intake for
protein is 0.8 grams per kilogram of body weight for adults.
The Basal Metabolic Rate, which is the amount of
calories the body expends at rest, meaning without performing any physical
activity, is influenced by the person's total weight and total amount of muscle.
The more muscle, the more calories a person can burn naturally. When the amount
of muscle is increased, then more calories can be ingested without gaining
weight. Conversely, if the amount of fat is increased, increasing the number of
calories ingested will only add weight.
Calories you eat equals pounds you carry
Since 3,500 calories equals about 1 pound of fat, if you cut 500 calories
from your typical diet each day, you'll lose approximately 1 pound a week (500
calories x 7 days = 3,500 calories). Simple, right? So why is weight loss so
All too often, we make weight loss much more difficult then it needs to be
with extreme diets that leave us cranky and starving, unhealthy lifestyle
choices that undermine our dieting efforts, and emotional eating habits that
stop us before we get started. But there’s a better way! You can lose weight
without feeling miserable. By making smart choices every day, you can develop
new eating habits and preferences that will leave you feeling satisfied—and all
while winning the battle of the bulge.