Diet Protocols and Weight Management Products: An Evidence-Based Narrative Review

Obesity is currently recognized as a chronic and multifactorial disease. According to epidemiological data released by the World Health Organization in 2022, more than 2.5 billion adults were overweight and more than 890 million were affected by obesity. The aim of this narrative review is to clarify what leads to overweight and obesity, to explain the concept of energy balance, to address the limited effectiveness of dietary products marketed for weight reduction, to examine commonly promoted nutritional strategies for weight loss and to challenge claims of their superiority. The most recent, robust, and high-quality evidence available on the topic was selected, with particular emphasis on systematic reviews and meta-analyses. Overweight and obesity are characterized by an excessive accumulation of fat mass. At the basis of excessive adipose tissue accumulation lies a persistent positive energy balance. Energy balance is generally considered a central physiological determinant of body weight regulation. Approaches that do not explicitly incorporate this principle may be associated with variable or unsustained outcomes. Available evidence suggests that, when an equivalent caloric deficit is achieved, differences in the timing of energy intake or in dietary patterns—such as intermittent fasting or low-carbohydrate diets—are not consistently associated with greater weight loss compared with other guideline-based dietary strategies. Some supplements supporting weight loss, in selected cases, may offer marginal support; however, based on the current state of scientific knowledge, no product represents an effective shortcut for weight loss.