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Caloric restriction remains a cornerstone of successful dieting and weight loss. This article considers the benefits and potential dangers of low-calorie diets.

Dieting — be it for health reasons or aesthetic reasons — has become a hot topic of discussion in modern societies. Studies, discussions and controversies follow one another and, in the mind of the lay community many doubts and misunderstandings persist. In fact, one could argue that misinformation is the main reason dieting raises so many questions. In the following paragraphs, we’ll try to break down the benefits and disadvantages of some of the most popular forms of dieting with the help of reliable scientific data.

First things first: what is dieting, exactly? Dieting can be defined as the practice of following a specific eating pattern according to a predefined set with the goal of losing, gaining or maintaining a certain weight.

If a person is on a diet, they’ll typically favor the ingestion of particular types of foods and beverages over others and, more often than not, this is paired with some form of physical exercise – especially if the aim is to lose weight.

Unsurprisingly, it’s weight loss diets that get the most attention. In fact, in light of escalating rates of obesity and its related co-morbidities, there has been an unprecedented quest for effective and safe weight-loss strategies by health-care practitioners, industry and the public. The most common weight loss diets can be divided in four large groups: low-fat diets, low-carbohydrate diets, low-calorie diets, and very low-calorie diets. Here we will consider the benefits and disadvantages of calories-restricting diets.

Low-Calorie Diets: How Low Should You go?

Low-calorie diets are those in which an individual reduces the daily caloric intake to an amount that is inferior to his or her previous intake or inferior to the average caloric intake of a person of their age. This practice, commonly known as caloric restriction, has gained widespread recognition in recent years, as research in several animal species has shown that caloric restriction without malnutrition increases one’s lifespan and improves their overall health state.

Traditional approaches to the weight loss have actually been based on the prescription of diets that provide an energy intake below that of an energy expenditure, i.e., an energy (or in common parlance calorie) deficit. Reducing the energy content of a diet can be achieved by reducing the intake of protein, carbohydrate, or fat alone or in combination. At the same time one or more macro-nutrients can be increased (within an overall energy restriction). Frequently, though, low-calorie diets encompass a balanced proportion of protein, carbohydrate, and fat in reduced amounts to provide an energy intake of 800 to 1500 kcal per day.

When done adequately, calorie restriction is the cornerstone of obesity therapy. It induces weight loss, therefore improving multiple metabolic risk factors for cardiovascular disease and other medical abnormalities associated with obesity.  Therefore, even if calorie restriction does not prolong maximum life span, it could increase life expectancy and the quality of late life by reducing the burden of chronic disease.

Going Too Low On Calories May Be Harmful

Restricting the consumption of calories must be done with great care, so as to avoid situations of malnutrition. The “Minnesota Starvation Experiment,” performed between 1944 and 1945, constitutes the very first systematic evaluation of the outcome of strict calorie restriction in individuals with normal weight. In this study, baseline calorie intake was reduced by 45% for 24 weeks in lean men. On one hand, these men exhibited the positive effects of calorie restriction, such as a decrease in body fat, blood pressure, improved lipid profile, low serum triglyceride concentration, decreased resting heart rate and lowered whole-body resting energy expenditure. On the other hand, this considerable calorie restriction also had severe harmful consequences, including anemia, muscle wasting, neurological deficits, lower extremity edema, weakness, dizziness, lethargy, irritability, and depression.

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