Methionine is a sulfur-containing branched-chain amino acid that must be ingested in the diet or as a supplement and is used for protein synthesis, including the formation of S-adenosyl methionine (SAM), L-homocysteine, L-cysteine, taurine, and sulfate. SAM has lipotropic effects potentially through its role as a methyl donor in lipid metabolism. When methionine donates a methyl group, VLDL and LDL cholesterol transport lipids from the liver. 

Inositol is a sugar alcohol that has many roles in the body, including affecting neurotransmitters in the brain, forming cell membranes, and glucose handling. Inositol may decrease insulin resistance, a condition that leads to high blood glucose levels. In clinical studies, it accelerated weight loss and reduced fat mass while upregulating genes involved in lipid metabolism and insulin sensitivity.

Choline is used to synthesize phospholipids which are essential components of cell membranes. The phospholipid, phosphatidylcholine, is also important in packaging fat consumed in the diet. Without adequate phosphatidylcholine, fat and cholesterol may accumulate in the liver. In addition, phospholipids are precursors to cell signaling molecules such as diacylglyceride and ceramide. Cells use these molecules to communicate their current status and requirements.

B12 is involved in many chemical reactions in the body, including ones associated with fat and carbohydrate metabolism and protein synthesis.

Acetylcarnitines transport fatty acids into the mitochondria. Fatty acids are oxidized in the mitochondria to produce adenosine triphosphate (ATP), the energy currency used by all cells in the body.

In addition to fatty acid metabolism, carnitine plays a role in carbohydrate metabolism. Carnitine helps maintain fluid balance inside and outside of the cells.

B12 is involved in many chemical reactions in the body, including ones associated with fat and carbohydrate metabolism and protein synthesis. Leading researchers to speculate that B12 deficiency (a relatively common problem) could make it harder for a person to lose weight.

Clinical tests show that there was an association between B12 deficiency and increased fat accumulation and obesity. A large study that enrolled 967 people showed that people with low B12 levels were at a higher risk for overweight and obesity.