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Obesity is on the rise. Weight loss remains the key in management of obesity. Dietary changes, including calorie restrictions, as well as regular physical activity are important measures for management of obesity.
Weight loss using calorie restriction includes diets low in calories and very low in calories termed Low calorie diet (LCD) and very low calorie diet (VLCD).
Weight loss more often than not may be reversed – or the lost weight regained, if the person is not careful about following the diet.
The use of very-low-calorie diets provide 800 or fewer calories per day and has been seen to prevent some of this regain. LCDs aim at providing 800 to 1200 kcal along with behaviour treatment and/or physical activity.
A low-calorie diet may be prescribed for an obese patient. An LCD must be lower than the person’s energy requirement and energy expenditure.
The measurements of resting metabolic rate (RMR) and measures of 24-h energy expenditure (EE) in metabolic rooms help in determining the level of intake that would allow maintenance of body weight and thus constitute the upper limit of low-calorie diet for a given subject. Diets consisting of between 800 and 1200 kcal/d are classified as LCDs.
The definitions of VLCD and LCD have changed with regard to the energy restriction level. VLCDs are now defined as total diet replacements with 800 kcal and 400 to 450 kcal per day. Meal replacements are limited to 200 to 400 kcal.
Low calorie diets differ in different groups like between men and women and adults and children.
The VLCD diet was first shown to be effective by Evans and Strang in 1929. The diet suggested by the duo was not too different from what is practiced today. This diet made from food ingredients comprising 400 kcal. The VLCD helps in reduction of 14 to 15 kcal/kg, resulting in weight losses of 2.5 to 3.5 kg/month. This diet reduced the energy intake to 6 to 8 kcal/kg to get a more rapid reduction.
In the 1970’s there was advent of hydrolyzed collagen as the only protein source and no inclusion of adequate amounts of vitamins, minerals, and electrolytes called the liquid-protein diet. This was unhealthy and resulted in too many complications.
Over time more nutritionally complete VLCDs have been developed with adequate loss of weight and no reported deaths. These new diets combined with other measures such as behavioural therapy as well as physical activity aim at effective weight loss at the start of the treatment and promote long-term weight control.
Some examples of VLCDs include:
These diets should only be undertaken for 12 continuous weeks, or intermittently (e.g. every two or three days alternating with a low calorie or normal diet).
Total calorie intake recommended is 2,000 for women, and 2,500 for men. VLCD aims at 800 which are substantially lower. Cutting calories drastically may lead to serious health problems.