A contributory reason to why food supplements and vitamins are too often a waste of money: magnesium stearate

Fat cells secrete an enormously important protein called FABP4 (alternative name is aP2). It is involved in metabolic syndrome, obesity, heart disease, hypertension, diabetes, and cancer. (See https://journals.sagepub.com/doi/full/10.4137/CMC.S17067). When we start releasing stored fat from our fat cells, it goes up. When we fast, it goes up. It appears to me that it stands in the way of weight loss by working together with PPAR-gamma to store lipids (See https://www.biorxiv.org/content/10.1101/2020.01.03.894493v1 and https://pubmed.ncbi.nlm.nih.gov/11872365/). So targeting FABP4 with various compounds has been the subject of much research. 

Many compounds that can inhibit FABP4 naturally occur in various foods, herbs, and spices that often pop up as associated with lower fat gain from hypercaloric and/or high fat diets. These compounds are easy to find for sale online and in vitamin stores. But they usually are sold in capsules that include magnesium stearate, an additive used to improve "flow" and make encapsulation easier. Unfortunately for everyone who finds that they seem to be wasting their money on vitamins, prescription pills, and supplements in pursuit of better health, magnesium stearate is quickly turned into magnesium and oleic acid in their bodies. Oleic acid stimulates FABP4 in the liver (https://www.nature.com/articles/s41388-018-0597-1, Supplemental Figure 3). Magnesium stearate also typically contains some palmitic acid (http://library.njucm.edu.cn/yaodian/ep/EP5.0/16_monographs/monographs_l-p/Magnesium%20stearate.pdf), which increases FABP4 in macrophages (https://pubmed.ncbi.nlm.nih.gov/31363792/). Pill "fillers" aren't the inactive substances that people tend to view them as.