User:LNguyen2021/Dieting

Types
A restricted diet is most commonly pursued by those who want to lose weight. Some people follow a diet to gain weight (such as people who are underweight or who are attempting to gain more muscle). Diets can also be used to maintain a stable body weight or to improve health.

Low-fat
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 over habitual eating.

A low-fat, plant-based diet has been found to improve control of weight, blood sugar levels, and cardiovascular health.

Low-carbohydrate
Low-carbohydrate diets are relatively high in protein and fats. Low-carbohydrate diets are sometimes ketogenic (i.e., they restrict carbohydrate intake sufficiently to cause ketosis). The rationale behind low carbohydrate diets is that they reduce overall glucose intake, thereby promoting reduced insulin secretion and increased glucagon secretion. This causes a metabolic shift to increased fat oxidation.

"The glycemic index (GI) factor is a ranking of foods based on their overall effect on blood sugar levels. The diet based around this research is called the Low GI diet. Low glycemic index foods, such as lentils, provide a slower, more consistent source of glucose to the bloodstream, thereby stimulating less insulin release than high glycemic index foods, such as white bread."

HP-LCDs such as the Atkins diet prescribe that >20% of energy intake is derived from protein-rich foods such as red meat, poultry, seafood, eggs, nuts, and seeds. Carbohydrate intake is severely limited, so foods such as starchy fruits and vegetables, legumes, grains, and sugar should be avoided. Overall, high protein with low carbohydrate intake diets (HP-LCDs) are effective for weight loss in the short-term, but have negative effects on metabolism and gut health. Therefore, they should only be considered in the early stages of weight loss regimens as a starting tool as evidence shows that calorie-restricted diets with balanced macronutrient compositions show similar weight loss over the long-term.

A randomized controlled trial comparing four diets concluded that the high-carbohydrate, low-glycemic index diet was the most favorable as it led to both high weight loss and a decline in low density lipoprotein.

The "glycemic load" is the glycemic index multiplied by the amount of carbohydrate. A meta-analysis by the Cochrane Collaboration concluded that low glycemic index or low glycemic load diets led to more weight loss and better lipid profiles but did not separate the effects of the load versus the index.

Adverse effects such as constipation, halitosis, headaches, muscle cramps, and weakness were commonly observed in patients on low-carbohydrate diets, along with an increase in mortality with long-term adherence.

Low-calorie
Low-calorie diets usually produce an energy deficit of 500–1,000 calories per day, which can result in a 0.5 to 1 kg weight loss per week. 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. Women doing low-calorie diets should have at least 1,000 calories per day and men should have approximately 1,200 calories per day. These caloric intake values vary depending on additional factors, such as age and weight.

Very low-calorie
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 – 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. There is some evidence that these diets results in considerable weight loss. These diets are not recommended for general use and should be reserved for the management of obesity 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.

The concept of crash dieting is to drastically reduce calories, using a very-low-calorie diet. Crash dieting can be highly dangerous because it can cause various kind of issues for the human body. Crash dieting can produce weight loss but without professional supervision all along, the extreme reduction in calories and potential unbalance in the diet's composition can lead to detrimental effects, including sudden death.

Fasting
Fasting is the act of intentional taking a long time interval between meals. Lengthy fasting (multiple days in a week) might be dangerous due to the risk of malnutrition. During prolonged fasting or very low calorie diets the reduction of blood glucose, the preferred energy source of the brain, causes the body to deplete its glycogen stores. Once glycogen is depleted the body begins to fuel the brain using ketones, while also metabolizing body protein (including but not limited to skeletal muscle) to be used to synthesize sugars for use as energy by the rest of the body. Most experts believe that a prolonged fast can lead to muscle wasting, although some dispute this. The use of short-term fasting, or various forms of intermittent fasting, have been used as a form of dieting to circumvent the issues of long fasting.

Intermittent fasting commonly takes the form of periodic fasting, alternate-day fasting, time-restricted feeding, and/or religious fasting. The effects of decreased serum glucose and depleted hepatic glycogen causing the body to switch to ketogenic metabolism are similar to the effects of reduced carbohydrate-based diets. There is evidence demonstrating profound metabolic benefits of intermittent fasting in rodents. However, evidence is lacking or contradictory in humans and requires further investigation, especially over the long-term. Some evidence suggests that intermittent restriction of caloric intake has no weight-loss advantages over continuous calorie restriction plans. For adults, fasting diets appear to be safe and tolerable, however there is a possibility that periods of fasting and hunger could lead to overeating and to weight regain after the fasting period. Adverse effects of fasting are often moderate and include halitosis, fatigue, weakness, and headaches. Fasting diets may be harmful to children and the elderly.

Exclusion Diet
This type of diet is based on the restriction of specific foods or food groups. Examples include gluten-free, Paleo, plant-based, and Mediterranean diets.

Plant-based diets include vegetarian and vegan diets, and can range from the simple exclusion of meat products to diets that only include raw vegetables, fruits, nuts, seeds, legumes, and sprouted grains. Exclusion of animal products can reduce the intake of certain nutrients, which might lead to nutritional deficiencies of protein, iron, zinc, calcium, and vitamins D and B12. Therefore, long term implementation of a plant-based diet requires effective counseling and nutritional supplementation as necessary. Plant-based diets are effective for short-term treatment of overweight and obesity, likely due to the high consumption of low energy density foods. However, evidence for long-term efficacy is limited.

The Paleo diet only includes foods that were available to our hunter-gatherer ancestors including meat, nuts, eggs, some oils, fresh fruits, and vegetables. Overall, it is high in protein and moderate in fats and carbohydrates. Some limited evidence suggests various health benefits and effective weight loss with this diet. However, similar to the plant-based diet, the Paleo diet has potential nutritional deficiency risks, specifically with vitamin D, calcium, and iodine.

Gluten-free diets are often used for weight loss but little has been studied about the efficacy of this diet and metabolic mechanism for its effectiveness is unclear.

The Mediterranean diet is characterized by high consumption of vegetables, fruits, legumes, whole-grain cereals, seafood, olive oil, and nuts. Red meat, dairy and alcohol are only recommended in moderation. Studies show that the Mediterranean diet is associated with short term as well as long term weight loss in addition to health and metabolic benefits.

Food group restricting
These diets are based on the restriction of specific foods or food groups. Examples include gluten-free, Paleo, vegetarian/vegan, and Mediterranean diets. Plant-based diets can range from the simple exclusion of meat products to vegan diets that only include raw vegetables, fruits, nuts, seeds, legumes, and sprouted grains. Exclusion of animal products can reduce the intake of certain nutrients, which might lead to nutritional deficiencies of protein, iron, zinc, calcium, and vitamins D and B12. Therefore, long term implementation of a plant-based diet may require nutritional supplementation as necessary. The use of plant-based diets is an effective treatment of overweight and obesity likely due to the high consumption of low energy density foods. However, evidence for long-term efficacy is limited. The Paleo diet only includes foods that were available to our hunter-gatherer ancestors including meat, nuts, eggs, some oils, fresh fruits, and vegetables. Overall, it is high in protein and moderate in fats and carbohydrates. Evidence demonstrates various health benefits and effective weight loss with this diet. However, similar to the plant-based diet, the Paleo diet presents potential nutritional deficiency risks, specifically with vitamin D, calcium, and iodine. Gluten-free diets are often used for weight loss but little has been studied about the efficacy of this diet and metabolic mechanism for its effectiveness is not clear. The Mediterranean diet is characterized by high consumption of vegetables, fruits, legumes, whole-grain cereals, seafood, olive oil, and nuts. Red meat, dairy and alcohol are only recommended in moderation. Studies show that the Mediterranean diet is associated with short term as well as long term weight loss in addition to its evidence-based health and metabolic benefits.