Liquid diets, which are often believed to help to lose weight or cleanse the body from toxins, have been widely practiced in recent days. So how do liquid diets actually affect health? What are the scientific facts?
What is liquid diet?
Liquid diet can be defined as diets in which all or most of the meals consist of liquid foods or beverages, or only liquid mixtures are consumed instead of meals. Liquid diets generally consist of fruit or vegetable juices (detox mixtures, smoothies, meal replacement shakes) or dairy products such as milk, yogurt and kefir or different water-soluble mixtures. Energy contents vary approximately between 500-1500 kcal. Liquid diets are preferred for fast weight loss or to remove toxic components from the body.
What is the nutrient content of liquid diets?
Liquid diets with a high content of fruits and vegetables are rich in vitamins A, C and potassium and antioxidants such as polyphenols, bioactive components that improve health and reduce the risk of chronic disease such as cardiovascular and diabetes. These diets are restricted to the consumption of grains, legumes, eggs, meat and fish, so liquid diets’ essential fatty acids content such as omega-3, omega-6 with group B vitamins such as B12, B6 and essential mineral content such as quality protein, iron and zinc may be limited. Their insoluble fiber may be low because whole grains are limited, and soluble fiber content because legumes are limited too. Liquid diets may be inadequate to provide the daily energy needs.
Liquid diets and health effects
Liquid diets may be preferred because they are easy to prepare and eat. Also, they make it easier to portion control that many people have difficulty in practice. In addition, because of their low energy content, liquid diets can be particularly effective in weight loss fast. However, it should be kept in mind that the losing body weight may be due to body water and muscle loss in the case of fast weight loss. In general, it is believed that liquid diets suppress hunger feeling and reduce food intake. However, researches show that liquid meals may cause increase in food consumption in the next meal. Very low energy content can be considered as the main health risk of liquid diets. It should be kept in mind that liquid diets may be inadequate to provide the protein needs, essential vitamins and minerals needed daily, lead to electrolyte imbalance and these may lead to significant health problems in a long term. Since liquid diets are restricted to whole-grains and legumes, they can be particularly restricted to insoluble fiber, this may lead to constipation and adversely affect the health of the digestive system.
What are the scientific facts?
The World Health Organization (WHO) states that all food groups should be eaten adequate and balanced for the maintenance of health and prevention of chronic diseases. In the management of body weight or weight loss, food variety and increasing physical activity with portion control are the most effective methods. Balanced nutrition and an active lifestyle play in important role in control of body weight as well as prevention of diabetes, cardiovascular diseases and cancer.
As a result, liquid diets or mostly liquid diets may be inadequate to provide nutrients such as energy, protein, essential fatty acids and especially iron, B12, zinc needed daily, and this may lead to health problems in a long term. Although it is seen as effective in fast weight loss, it can actually cause loss of muscles and body water and may not commit permanent weight loss. Individuals with insulin resistance, diabetes or any other chronic disease should be careful about liquid diets. There are clinical studies suggesting that liquid diets have positive effects on metabolic indicators such as cholesterol, blood fats as well as body weight in a short term, however, evidence-based data showing which results can occur in a long term are not enough. In order to control the body weight and protect health, it is important to have adequate and balanced eating habits personalized to age, gender, health status and lifestyle of the individual and maintain an active lifestyle.