How do the most popular diets work?

For someone who plans to lose weight, the diet world looks like chaos. Fortunately, there are as many diets as their names.
In this article, we will talk briefly about popular diets for weight loss and what science says about them. Diets are described by type, not by name. The names can be different, but any of them can be classified into one of the groups described below.

Very low-calorie diets

How do the most popular diets work?

For several decades, this approach has been used in medical practice to treat obesity. The goal is to quickly lose the first kilograms (average of 1 to 2.5 per week) and keep the muscles as strong as possible. With extreme caloric restriction, muscle loss accounts for up to 25% of total weight loss. However, if a diet is combined with strength training and a sufficient amount of protein in the diet, the muscles can be preserved, as studies have shown. On this diet, the caloric value of food is no more than 800 kcal/day. At the same time, there is a lot of protein in the food – 70-100 g / day and more. Fats can be up to 15 grams, and carbohydrates – 30-80 grams. If weight loss occurs in the clinic, the diet is replaced by special cocktails and bars, enriched with all necessary vitamins and minerals. For people with clinical obesity, this diet is a potentially powerful tool that helps to quickly lose a few kilograms. It is beneficial when obesity threatens health, as well as to motivate people to continue to lose weight when they see fast results. And for type 2 diabetes, it helps to improve glucose metabolism faster. But a very low-calorie diet works well in the short term, at the beginning of weight loss and has no long-term weight loss benefits (from a year or more). How long can I stay on this diet? In clinical practice, doctors use 8-12 weeks, which usually leads to a loss of 1.5-2.5 kg per week. After that, it is worth switching to a less strict calorie restriction. It is not recommended to use such a diet by yourself. If the excess weight is small, they will not bring additional benefit. In case of obesity, you should consult a doctor.

Diets with low fat content

This is a diet in which fats account for 15-30% of all calories received. Thus, when eating 1400 calories it is about 20-40 grams of fat per day. Although doctors recommend obese patients to reduce fat in their diet since the 50s of last century, the official recommendations for a healthy diet in the U.S. included this item only in the 80s of last century, when there was enough data accumulated on the benefits of reducing fat. Fats are the most calorie macronutrients (9 calories per gram of fat), so reducing them is an easy way to make food less caloric and eat less. In a controlled study, scientists gave people the same meal visually and taste, but with different amounts of fat. A diet with higher fat content resulted in weight gain and/or less fat loss. However, in the long run, “non-fat” diets do not lead to greater weight loss than the usual calorie limit. The difference detected is often less than a kilogram and has no practical meaning.

Low-carbohydrate diets

How do the most popular diets work?

Scientists do not yet agree on the exact amount of carbohydrates that make a low-carbohydrate diet. The Institute of Medicine’s Food and Nutrition Board has established a range of “normal” consumption of carbohydrates for adult lules at 45-65% of total calories. Therefore, everything below can be considered low-carbohydrate. In the scientific literature, a low-calorie diet is a diet in which carbohydrates account for less than 40% of energy. If we talk about the number of carbohydrates in grams, this is all that is less than 200 grams per day. Some specialists give figures of 50-150 grams of carbohydrates per day. In any case, meta-analyses (analyses of the accumulated research on the subject) compared the weight loss effect in low-fat and low-carbohydrate diets and found no differences. The results were similar, and no metabolic advantages of low-carbohydrate diets were found in healthy people. A low-carbohydrate diet works to the extent that it limits calories. There are several explanations for why it is considered particularly effective. The first one is simplicity. The simpler the dietary rules, the better and longer a person follows the diet and loses weight as a result. Therefore, “there are fewer carbohydrates” is one of the easiest and most understandable ways to reduce caloric intake. A person removes cupcakes, doughnuts, chips, white bread and baked goods – everything that brings a lot of calories (many of these products have a lot of fat at the same time), but it is poorly saturated, forcing to eat more during the day. The second is the loss of glycogen and water on a low-carbohydrate diet, which reduces up to 3 kg on the weight, but not due to fat.