All cooking oils naturally contain small quantities of diacylglycerols (DAG), ranging from 0.8% in rapeseed oil to 9.5% in cottonseed oil.39 In addition, DAG is produced in the digestive tract as a metabolic intermediate, as 1,2-diacyl-sn-glycerol (1,2-DAG) or 2,3-diacyl-sn-glycerol (2,3-DAG), after the ingestion of TG.40 In recent years manufacturers have developed an enzymatic process to produce 1,3-diacyl-sn-glycerol (1,3-DAG) by migration of the acyl group with the reverse reaction of the 1,3-specific lipase. DAG oil can be easily incorporated into food products since it is similar in taste, appearance, and fatty acid composition to other oils.

It is the specific structural differences of DAG isomers and not the fatty acid composition of DAG or TG that appear to explain the different action on lipid metabolism and body weight. The main end products of lipase action on 1,3-DAG are glycerol and free fatty acids, which may be less readily re-synthesized to chylomicron TG. Moreover, larger amounts of fatty acids from digested DAG may be released into the portal circulation rather than being incorporated into chylomicrons, compared with TG oils. In addition to producing lower TG content of chylomicrons, lower serum TG levels in a fasted state and in the postprandial state occur after DAG ingestion. This hepatic exposure to fatty acids by increasing DAG intake may lead to greater fat oxidation by the liver than following TG intake. Enhanced fat oxidation may lead to increased satiety. Thus, decreasing caloric intake may induce a decrease in weight and fat loss in long-term DAG feedings.

While certain studies indicate that 1,3-DAG has a positive outcome in animal and human trials, other studies show no effect on body weight63-67 or TG levels. This lack of effect may be due to insufficient doses used (10% in the diet) or the heterogeneity across subjects used including overweight or obese versus normal weight individuals. Overweight and obese subjects could have defective fat oxidation; thus, higher fat oxidation may produce greater weight loss. Although the use of DAG oils for weight control is promising, much remains to be clarified regarding the mechanism of dietary DAG.

DAG oil studies do not indicate any severe adverse health effects related to its consumption. However, it still remains to be seen how DAG oil intake will affect humans on a long-term basis as well as synergistically with other nutrients.

Overall, DAG oils are easily incorporated into foods without affecting palatability, but have slightly higher costs than conventional oils. The AECES model for DAG shows it being a generally appropriate functional food for weight control; however, DAG oil has not yet been a huge success with consumer acceptance due to conflicting studies on the efficacy of the product. Overall, DAG oil demonstrates potential as a weight loss agent, but future research is needed to elucidate mechanisms responsible for its action on weight loss.