Diets to promote weight loss are generally divided into four categories: low-fat, low-carbohydrate, low-calorie, very low calorie and more recently flexible dieting.
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 2–4 kilogram weight loss in all studies.
At two years, all calorie-reduced diet types cause equal weight loss irrespective of the macro nutrients emphasized.
In general, the best diet is one where you find a way to eat fewer calories in any way that you can.
A study published in the APA's journal American Psychologist found that dieting does "not lead to sustained weight loss or health benefits for the majority of people."
Types of Diets
However, other studies have found that the average individual maintains some weight loss after dieting.
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 3.2 kg (7.1 lb) over habitual eating.
Low-carbohydrate diets such as Atkins and Protein Power are relatively high in protein and fats. 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 0.5 kilogram (1.1 lbs) to 1 kilogram (2.2 lbs) weight loss per week. Some of the most commonly used low-calorie diets include DASH diet 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 3–12 months.
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 loss of 1.5–2.5 kilograms (3.3–5.5 lb) per week. "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 totally fasting, after which 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
Detox diets claim to eliminate undesirable "toxins" from the human body rather than claiming to cause weight loss. Many of these use herbs or celery and other juicy low-calorie vegetables.
Religious diets. Religious scripture may be a factor in motivating people to adopt a specific diet. For example, the Biblical Book of Daniel (1:2-20, and 10:2-3) refers to a 10 or 21-day avoidance of foods (Daniel Fast) declared unclean by God in the laws of Moses.
In modern versions of the Daniel Fast, food choices may be limited to whole grains, fruits, vegetables, pulses, nuts, seeds and oil. The Daniel Fast resembles the vegan diet in that it excludes (fasts from) the consumption of foods of animal origin.
The passages strongly suggest that the Daniel Fast will promote good health and mental performance.
Nutrition diets. Weight loss diets that manipulate the proportion of macronutrients (low-fat, low-carbohydrate, etc.) have been shown to be more effective than diets that maintain a typical mix of foods with smaller portions and perhaps some substitutions (e.g. low-fat milk, or less salad dressing). Extreme diets may, in some cases, lead to malnutrition.
Nutritionists also agree on the importance of avoiding fats, especially saturated fats, to reduce weight and to be healthier.
They also agree on the importance of reducing salt intake because foods including snacks, biscuits, and bread already contain ocean-salt, contributing to an excess of salt daily intake.
One of the most important things to take into consideration when either trying to lose or put on weight is output versus input. It is important to know the amount of energy your body is using every day, so that your intake fits the needs of ones personal weight goal. Someone wanting to lose weight would want a smaller energy intake than what they put out.There is no specific diet everyone should be on, because everyones bodies vary, as do their intake requirements. A more active person will burn more energy and in return need a higher intake.
Food diary. A 2008 study published in the American Journal of Preventive Medicine showed that dieters who kept a daily food diary (or diet journal), lost twice as much weight as those who did not keep a food log, suggesting that if you record your eating, you wouldn't eat as many calories.