**2. Meal replacements for weight loss and weight maintenance**

According to the most recent global analysis, obesity rates continue to rise at an alarming level overall, reaching 50% of the population in some countries (**Figure 1**), with the prevalence in women rising faster than that for men. Globally, the prevalence of obesity now exceeds that of underweight (NCD Risk Factor Collaboration 2016). Although obesity rates in some developed countries appear to have leveled off (e.g., US men) [1], comorbidities, such as type II diabetes, continue to rise. The World Health Organization (WHO) estimates the prevalence of diabetes has doubled worldwide since 1980 and resulted in 3.7 million deaths in 2012, with combined direct and indirect costs estimated in the \$billions annually [2]. With overweight and obesity recognized as the strongest risk factors for type II diabetes, the WHO recommends obesity prevention, through healthy diet and physical activity, as a key approach.

Few tools have been validated as safe and effective in the treatment or prevention of obesity and overweight. Bariatric surgery is effective at treating those who are morbidly obese, yet it is associated with substantial risks and postsurgery complications, including nutrient deficiency. While advances in science and technology have eventually provided several efficacious pharmaceutical drugs for obesity treatment, the effects are modest and associated with a myriad of side effects [3], and many FDA‐approved prescription weight loss drugs have been subsequently withdrawn from the market due to safety concerns [4]. In contrast, nearly 150 studies demonstrate that use of MR (in various forms) safely reduces energy intake and results in sustainable weight loss (**Table 1**). A systematic review published concluded that MR safely and effectively produce sustainable weight loss [5]. The systematic review included six randomized, controlled MR intervention studies of at least 3 months duration, involving adults with a body mass index (BMI) ≥ 25 kg/m2 .

mass and reducing visceral body fat during weight loss. This review focuses on MR that do

Depending on the formulation, MR also possess the advantage of having a low glycemic index (GI) value; low‐GI diets have been linked to improved weight maintenance and reduction in risk of diabetes and ocular disease. Many nutrition researchers and authoritative bodies around the world have highlighted the need to improve the nutrient density of diets as a means to reduce obesity while maintaining optimal nutrition status. MR also tend to be nutrient dense, meaning that they possess a high ratio of essential nutrients relative to calories.

Some markets have established clear regulatory standards and definitions for the composition and marketing claims for MR (e.g., Codex, Canada, EU, Brazil, Korea, Indonesia). However, several large markets (e.g., US, Mexico, China, Russia, India) still lack these important standards, in turn limiting research opportunities and recognition by governments, healthcare

The aim of this chapter is to review the extensive body of literature validating the safety and effectiveness of MR as weight loss and weight maintenance tools; explore the benefits of MR beyond weight loss, including maintenance of lean body mass and low glycemic index; discuss the concept of nutrient density, its importance in nutrition and how MR fit into a nutrient‐dense diet; and discuss the need for regulatory standards to be established in those

According to the most recent global analysis, obesity rates continue to rise at an alarming level overall, reaching 50% of the population in some countries (**Figure 1**), with the prevalence in women rising faster than that for men. Globally, the prevalence of obesity now exceeds that of underweight (NCD Risk Factor Collaboration 2016). Although obesity rates in some developed countries appear to have leveled off (e.g., US men) [1], comorbidities, such as type II diabetes, continue to rise. The World Health Organization (WHO) estimates the prevalence of diabetes has doubled worldwide since 1980 and resulted in 3.7 million deaths in 2012, with combined direct and indirect costs estimated in the \$billions annually [2]. With overweight and obesity recognized as the strongest risk factors for type II diabetes, the WHO recommends obesity prevention, through healthy diet and physical activity, as a key approach.

Few tools have been validated as safe and effective in the treatment or prevention of obesity and overweight. Bariatric surgery is effective at treating those who are morbidly obese, yet it is associated with substantial risks and postsurgery complications, including nutrient deficiency. While advances in science and technology have eventually provided several efficacious pharmaceutical drugs for obesity treatment, the effects are modest and associated with a myriad of side effects [3], and many FDA‐approved prescription weight loss drugs have been subsequently withdrawn from the market due to safety concerns [4]. In contrast, nearly 150 studies demonstrate that use of MR (in various forms) safely reduces energy intake and results in sustainable weight loss (**Table 1**). A systematic review published concluded that

not require medical supervision (those classified as medical foods).

258 Superfood and Functional Food - An Overview of Their Processing and Utilization

professionals and consumers of the value the category provides.

**2. Meal replacements for weight loss and weight maintenance**

countries that currently lack a definition for MR.

**Figure 1.** World Health Organization Global Health Observatory (GHO) data. Global overweight and obesity prevalence. *Source*: World Health Organization http://www.who.int/gho/ncd/risk\_factors/overweight/en/.


**Table 1.** Relative comparison between pharmacological, surgical and meal replacement approaches to obesity treatment and prevention.

More recent studies have demonstrated MR effectiveness at maintaining weight loss up to several years. Intervention studies involving MR use with a year or more of follow‐up have shown a range of sustained weight loss from 2% up to 11% of baseline body weight (**Figure 2**) [6–21].

**Figure 2.** Weight loss and maintenance from randomized controlled trials ≥1 year in duration involving meal replacement.

Portion size is a key factor in determining energy intake and may be closely linked to obesity. Research indicates that portion size is directly correlated with energy intake, suggesting that controlling portion size is an effective approach to reduce energy intake and combat obesity [22]. Among the few portion control tools researched to date, liquid MR are considered among the most effective and consistent, particularly if combined with other efforts to encourage consumption of high‐nutrient‐dense, low‐energy‐dense foods [22]. Furthermore, MR promote adherence to a restricted calorie diet due to simple preparation and convenience compared to preparing and cooking low‐calorie foods at home. MR generally contain a tight range of total calories, macro‐ and micronutrients (**Figure 3**), and are a nutrient‐dense tool, especially useful for supporting adherence to a calorie‐restricted diet through portion control.

Satiety and appetite are known to impact total energy intake, as well as food choices and eating behavior. Both are regulated by a combination of mechanical and endocrine effects ranging from the gut to the brain. With respect to diet, protein has been identified as an important contributor to satiety, defined as the absence of hunger between meals. Dietary protein can induce satiety through several mechanisms including thermic effects and induction of gut hormones such as cholecystokinin (CCK) and glucagon‐like peptide 1 (GLP‐1) and ghrelin [23]. Intervention studies show that increased protein intake, using protein‐enriched MR, is effective at increasing satiety, reducing hunger sensations, decreasing energy intake and facilitating weight loss in obese subjects [24, 25].

Many authoritative bodies around the world have sanctioned the use of MR for weight loss and control. As far back as the mid‐1980s, Codex Alimentarius recognized the use of MRs for weight control [26]. In 2010, the European Food Safety Authority (EFSA) concluded that MR are effective for both weight loss and weight maintenance [27]. Most recently, the Academy of Nutrition & Dietetics (AND) rated strongly the use of MR as part of a comprehensive weight management program [28].

**Figure 3.** General macro‐ and micronutrient composition of meal replacement products.
