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Low carbohydrate diet as influencing weight loss and/or body composition
Definition of low carbohydrate diet There is a general definition of low carbohydrate diet. The dietary guidelines recommend carbohydrates should be consume 45 to 65 percent of total energy intake. If a 2000 kcal is regular calorie consumption per day, it would be 900kcal to 1300kcal. If a low carbohydrate diet is initiated, the diet should be restricted the type and amount of carbohydrate intake, so it will be less than 45-65 percent of total energy intake. Also, if there is low carbohydrate diet starts, it has relatively high fat and protein intake. A low carbohydrate diet is helpful for a person who has a type 2 diabetes and metabolic syndrome due to weight loss. Definition of low carbohydrate in recent studies In study 1 defines low carbohydrate diet is associated with reduction in glycogen storage and causes decline in physical activity. This eventually causes an increase in metabolic rate.
Activity was not affected by diet, but metabolic rate is reduced; this is called metabolic depression and explain the decline effectiveness of low carbohydrate diet for long term but effective in short term. In study 2 defines low carbohydrate diet is a emulation fasting by restricting carbohydrate and increase fat and protein intake because very low calorie diet has a primary concern that such this diet is lost together with fat mass. Therefore, study 2 gives the aim to promote loss of fat mass but preserve of muscle mass(Diego Gomez-A et al., 2017). In study 3 defines low carbohydrate diet is effective than low calorie diet after 1 and 2 years follow up because it will preserve muscle mass but expenses of fat mass and visceral mass. In study 4 defines low carbohydrate diet is low carbohydrate with high fat diet is very popular and not new for weight loss.
It is effective for improving triglycerides levels, high-density lipoprotein cholesterol, and glycemic control(Cary Xinn et al., 2017). Study 5 defines low carbohydrate diet is feasible alternative to a low fat diet for weight loss and have favorable metabolic effects, however long term is lacking. So, there is alternative diet which is mediterranean diet gives beneficial for weight loss(Shai I et al., 2008). Mechanism of Action In study 1, low carbohydrate and high protein diet causes satiation. Appetite is satisfied by the order of protein, carbohydrate, and fat.
There are different pathways by which macronutrients are oxidized, net ATP yields vary per calorie of a given substrate with protein yielding comparatively less ATP. This will increase resting energy expenditure and it attributes to gluconeogenesis in response to lowered glycogen storage and eventually cause reduced carbohydrate intake(Winwood-Smith H et al., 2017). In study 2, VLCK diet would cause an increase in diuresis because glycogen is stored together with water. Water loss is associated with ketonuria because ketone bodies increases the renal sodium and water loss as a result. In study 3, low carbohydrate diet induces a shift in metabolism and the production of plasma ketone bodies.
Glucose constitutes the central nervous system which is very important for energy utilization process but cannot use fatty acids as energy source, so CNS system needs alternative fuel source. Therefore, ketone replace the depletion of glucose and fulfill most of the body energy requirements. A person who are doing low carbohydrate diet will experience ketonemia without acidemia. (Diego Gomez-A et al., 2017). In study 4, a result of the reduction in glycogen storage, there is water storage will be reduced also.
LCHF diet also produce physiological and hormonal changes. Insulin becomes down-regulated as hepatic glucose is reduced. With decline of insulin, energy-deficit condition is initiated and fat uses as body fuel instead of carbohydrate. A final possible mechanism is LCHF causes increase calorie expenditure, so it is attributed to metabolic efficiency (Caryn Zinn et al 2017). In study 5, HDL cholesterol increases during weight loss and maintain phases in all groups along with greatest increase in low-carbohydrate group. However, triglyceride level decreased in low carbohydrate group as compared with low fat group. Leptin reflects body fat mass decreased significantly in all group (Shai I et al., 2008) . Summary of Recent Literature In study 1, population is used D. melanogaster which are flies in Australia. There are 600 total were placed into the bottle for mass-bred population. Flies were fed one of two diets: a standard diet with protein-to-carbohydrate ratio of 1:4 and low-carbohydrate diet with a protein-to-carbohydrate ratio of 1:1.
There are some major findings. 1) a low carbohydrate and high protein diet results in reduction glycogen storage which causes reduction in physical activity. 2) low carbohydrate diet compared with calorie-restricted diet is more effective for short term but in a long run, this advantage is reduced or no longer apparent due to glycogen deficit (Winwood-Smith H et al., 2017). In study 2, population ages from 18 to 65 years old. Body Mass Index should be greater than 30kg/m2 with stable body weight in the previous 3 months. In step 1, the patients had high biological protein intake five times per day. In step 2, protein intake is replaced by a natural protein such as meat or fish at lunch or dinner. In step 3, a second serving of low-fat and natural protein were replaced the second serving of biological protein. In steps 4 and 5, ketogenic phase is initiated, and physician should measure the weight loss and starts low-calorie diet around 800-1500 kcal/day. After four visits, there was a severe reduction in body weight due to fat mass reduction around -20.2 kg as assessed by DXA. There are some major findings. 1) there is significant weight loss in total fat mass and visceral fat tissue. 2) adequate muscle strength is preserved during the diet(Diego Gomez-A et al., 2016) In study 3, populations are 20 obese and 12 females and age from 18 to 58 years old. At average, patients are 95.9 +/- 16.3 kg and BMI is 35.5 +/- 4.4.
The blood pH is not significantly different from normal range. A blood pH less than 7.30 is defined as diabetic ketoacidosis, but there is no individual had a measurement below this level. In this study, there is not significant variation in bicarbonate and lactic acid values. This observation shows the acceptable insulin function a ketogenic diet induces a well-tolerated ketosis rather than ketoacidosis (Gomez-Arbelaez et al., 2017). In study 4, populations are 41 total individuals who were sent an information sheet, consent form,and screening questionnaire via email. Participants are excluded if they consume 250g or less of carbohydrate and BMI < 25. There are two different groups, and control group participants had low-fat, high-carbohydrate dietary approach.The other group has a LCHF dietary approach with moderate carbohydrate restriction. The major findings are 1) VLCK diet is safe diet inducing a severe weight loss without altering acid-base balance.(Zinn C.,2008) In study 5, population age ranges from 40 to 65 years old, and BMI should be at least 27 or higher or with having type 2 diabetes or coronary heart disease. There are three different diets to compare difference and effectiveness of weight loss.
Low fat diet aimed energy intake of 1500kcal per day for women 1800kcal for men with 30% of calories from fat, 10% from saturated fat and intake of 300mg of cholesterol per day. Mediterranean diet is moderate fat, restricted calorie diet and have high consumption of vegetables and low in red meat and poultry. This diet restricts calories from fat no more than 35%. Low carbohydrate diet aims to provide 20g of carbohydrate per day, and intakes of calories, fat, and protein are not limited. Major findings are 1) twenty participants initiated blood-pressure treatment, five people initiated medications for glycemic control, and one individual reduce the dosage of medication for glycemic control. 2) For low fat diet group had −2.9±4.2 kg, −4.4±6.0 kg for the Mediterranean-diet group, and −4.7±6.5 kg for the low-carbohydrate group. (Shai I e., 2018)
Overall, recent literatures have shown that low carbohydrate diet causes weight loss effectively. It reduces total fat mass and visceral fat tissue, but it maintains muscle strength. Also, this diet is safe diet for the obesity due to acid-base equilibrium. Also, mediterranean and low carbohydrate diet are effective diet and safe compared with low fat diet for weight loss. However, this diet is not recommended for long term because it will rebound the weight and does not preserve constant weight loss as long term.
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