Over one-third (36.5%) of the US adult population are obese as categorized by having a body mass index (BMI) ≥ 30 kg/m2
]. The most common causes of obesity are overeating and physical inactivity. However, ultimately, body weight and its composition are the result of genetics, metabolism, environment, behavior, and culture. It is well recognized that obesity not only has a significant, adverse impact upon disease risk, but also has important consequences for morbidity, disability, emotional well-being, and quality of life. Therefore, efforts to prevent, reduce or intervene in weight gain and obesity are at the forefront of public health concerns.
Due to the great cost to both physical and psychological health, an abundance of clinical studies have been conducted on various interventions to improve body weight and composition. Focusing on body composition is essential because even more important than overall weight loss is sustainably losing fat mass (FM) while maintaining lean body mass (LBM). Most popular commercial weight loss programs are marketed as being able to reduce body weight within the first few weeks; however, of the weight lost, a significant amount includes losses in both LBM and FM, as well as changes in fluid status. Much of the early research utilized weight loss interventions that were designed around dietary changes that focused on calorie restriction and outcomes focused primarily on total body weight changes as opposed to body composition changes [2
]. This approach was found to be misleading and potentially detrimental to health due to the fact that substantive reductions in LBM also occurred and weight lost was often quickly regained [3
The loss of LBM is problematic for a number of reasons, including impacts on health, ability to conduct activities of daily living and potential effects on emotion and psychological states. The loss of LBM impedes sustainability by causing lowered resting energy expenditure/metabolism, fatigue, declines in neuromuscular function, and increased risk for injury [4
]. Moreover, the metabolic decline that occurs after LBM loss results in a subsequent body fat overshoot, or a regain in fat mass [6
], thereby resulting in unfavorable, compounded changes in body composition. Therefore, in order to enhance sustainability of any weight loss program, and to offset any potential negative health consequences, it is important to prevent the loss of LBM. In an effort to offset this LBM loss, several studies have incorporated exercise in conjunction with a weight loss program; however, this has only provided modest outcomes, most likely due to the modest caloric expenditure experienced with moderate exercise [7
]. Various dietary supplement products have also been researched to augment weight loss or improve body composition with varying levels of success. Some well-studied weight loss and body composition dietary supplements include, but are not limited to, fiber complex, green tea, Garcinia cambogia, Irvingia gabonensis
, and chromium picolinate.
Of these products, chromium picolinate (Chromax®
, Purchase, NY, USA; CrP) has been shown to help individuals lose fat and overall body weight while also preserving lean muscle mass. It has been reported that supplementation with 200–400 mcg chromium/day as chromium picolinate improves body composition [8
], which is an important aspect for overall metabolic health and, therefore, weight loss and maintenance. Dietary chromium is an essential nutrient with recommended daily intakes of 50–200 mcg chromium/day. It has been shown to play an important role in glucose, lipid, and amino acid metabolism by its potentiating effects on insulin action [9
]. However, the dietary intake of chromium is typically suboptimal as few diets contain even the minimum of 50 mcg [9
]. Since most people consume half of the recommended amount, the likelihood of chromium supplementation being beneficial is increased. Therefore, adding bioavailable forms of chromium to the diet is vital for individuals to benefit from the effects of chromium on body composition.
To increase the bioavailability of chromium, it was added to picolinic acid, a naturally occurring metabolic derivative of tryptophan. Combining picolinate acid with chromium in the form of chromium picolinate (CrP) enhances the bioavailability of chromium compared to other salts of chromium, and by doing so improves insulin utilization and efficiency in humans and animals [10
]. Many studies which have reported beneficial effect of CrP have been performed in preclinical models. Improving insulin utilization can positively influence body composition because of the role insulin plays in the endogenous synthesis of fatty acids and triglycerides, as well as increasing muscle protein synthesis [11
]. CrP has been extensively studied for its ability to enhance body composition and in over thirty-five human clinical trials has been shown to enhance weight loss, caloric reduction, and carbohydrate and glucose metabolism, among various other benefits. Not all studies report weight loss with chromium supplementation, including a systematic review of overweight and obese subjects that had a narrowed search criteria to studies focusing on weight loss, not LBM or body composition changes, which is focused on in this paper [13
]. In a key clinical study, CrP supplementation not only lead to weight loss, but also favorable body composition changes, as the weight lost was 98% FM and only 2% LBM [14
Based on the understanding that the decline in LBM during weight loss can negatively affect various physiological processes and in turn, hinder weight loss maintenance and healthy body composition, the purpose of this brief review is to evaluate the impacts of various dietary strategies on LBM as well as popular dietary supplements often used as adjuncts to improve weight loss outcomes including maintenance of LBM. Pub Med and Google Scholar were searched for the following terms: weight loss and lean body mass; weight loss and body composition; as well as weight loss and lean body mass associated with each supplement and dietary strategy covered.
It is well recognized that obesity not only has a significant, adverse impact upon disease risk but also has important consequences for morbidity, disability, emotional well-being, and quality of life. Therefore, efforts to address the issue have received much attention in the literature. While various weight loss programs have resulted in short term success, many fail to result in long term weight loss. One of the suggested reasons for this lack of long term success is the loss of LBM that occurs with the weight loss. Therefore, recent focus in the weight loss literature has been not just on total weight loss but on improving body composition. Focusing on the effects of any weight loss effort on body composition changes is essential because even more important than short term weight loss is sustainably losing FM while maintaining LBM.
Many different programs and interventions have tried to offset the loss of LBM commonly experienced as part of hypocaloric popular weight loss programs through methods including dietary manipulation, especially augmented protein intake, exercise, and dietary supplements. There are a few dietary supplements that appear to help preserve LBM during weight loss or to reduce the loss of LBM as compared to diet alone. One such dietary supplement that appears to have this “LBM sparing” effect is chromium picolinate. For the reasons shared in this paper, it seems logical to include CrP as part of any reduced calorie (diet) plan as a means of keeping metabolically active LBM. Weight loss without CrP may be at the cost of LBM, thus, this adjunctive strategy appears worthy of further research and applied practice. A comprehensive approach, integrating evidence-guided macronutrient and calorie intake, resistance exercise, and chromium picolinate may be the most effective approach to preserving or increasing lean body mass while maximizing body fat mass reductions.