There have been several meal replacements for many years. There are shakes, soups, bars, powdered food… various forms of products that are promoted as meal replacements for weight loss. The intention of these products is that people stop consuming one meal (such as dinner) or even all meals and consume these products instead.
There are countless patients who use or at some point in life have already sought these products to try to lose weight. The big question is: do they work? Can they be used as a nutritional strategy?
First, we need to define what it means to “work”. It is important to make it clear that just losing weight is not working. Virtually any supplement, fad diet or nutritional strategy promotes weight loss, greater or less than others. This is mainly due to the caloric deficits imposed by them. It turns out that these losses are only initial, there is usually a regain of weight afterwards. There are different definitions for effectiveness in the scientific literature, but in general there must be a loss of at least 5% of weight and that is sustained after 1 year or 2.
To assess the effectiveness of meal replacements, we will analyze the study : the authors conducted a systematic review with meta-analysis of randomized controlled trials and observational studies of weight loss programs, including meal replacements. The results showed that, on average, 36% of patients using these products were unable to lose more than 5% of their weight in different periods (between 12 and 48 weeks).
This is a considerable number, but something is between the lines and deserves to be discussed: the number of patients who abandon this type of study. Overall, the dropout rate was 7 to 91%! In studies with meal substitutes specifically, it reached 40%. This is a very serious fact, not only because it masks the final success rate, but it also shows that almost half of people do not adapt to the use of shakes and others as a meal. This is an important point about the effectiveness of these substitutes: few people manage to maintain them in the medium term.
Now, the main point is that there is an important weight regain after these interventions. One reason is abandonment, as shown above. Nobody can eat powder and shake for long. This goes against everything we believe as nutritionists: food is not only a nutrient, it is also emotion, feeling, pleasure, culture, psychological, social. It is something that affects all the senses of the body. Food is not only physically nourishing, it is an important factor for human experience.
Another aspect is that, depending on the nutritional composition of these products, weight loss may be due to loss of water and muscles. A marked caloric deficit, without physical activity and with inadequate supply of macro and micronutrients favors muscle loss. That is, the person does not lose weight, he malnourishes. With less muscle mass, the scale shows less weight, but the fat is still there. This is problematic, as muscle mass controls the resting metabolic rate and various metabolic aspects. With less muscle mass the chance of having an accordion effect is very high.