Obesity is determined by excessive fat storage in adipose tissue with BMI≧25. Diagnostic criteria of “Obesity Disease” are follows; a medical condition associated with obesity-related diseases or a high probability of their development and, from a medical point requires weight reduction. “Obesity Disease” is treated as a clinical entity in Japan.
In healthy adipose tissue, small adipocytes secrete anti-inflammatory adipokines. But, excessive fat accumulation in adipose tissue, especially in visceral adipose tissue, secretes pro-inflammatory adipokines, and adipocytes undergo apoptosis. Macrophages invade the area around the apoptotic cells and cause inflammation. The inflammatory foci secrete pro-inflammatory adipokines more and more. Chronic spread of pro-inflammatory adipokines causes lifestyle-related diseases such as diabetes, dyslipidemia, and hypertension, and leads to the development of atherosclerotic diseases and cancer. Viral infections acutely spread large amounts of pro-inflammatory cytokines from visceral adipose tissue, causing a cytokine storm, making obese individuals more susceptible to severe disease.
Inflammation caused by fat accumulation is a threat to obese people both chronically and acutely. Obese people need weight reduction treatment to prevent the onset and aggravation of obesity-related diseases, and viral infection.

In a human intervention study in which barley containing β-glucan was consumed, the following obesity-related indicators were improved: 1) suppression of raised postprandial blood glucose, 2) reduction of serum LDL-cholesterol concentration in hypercholesterolemic men, and 3) reduction of visceral fat area in men and women with a visceral fat area of 100 cm² or more. These results demonstrate that barley consumption is effective in improving obesity-related indicators. In animal experiments, it was thought that the likely mechanism was the inhibition of digestion and absorption of barley, which depends on the molecular weight of β-glucan, and the improvement of glucose and lipid metabolism by short-chain fatty acids derived from intestinal fermentation. It was speculated that the improvement in glucose metabolism by barley consumption was mainly due to the delayed absorption of glucose and gastrointestinal hormones, such as GLP-1, with changes in gene expression having less influence. On the other hand, it was speculated that the decrease in cholesterol concentration in the liver and serum was due to the increase in short-chain fatty acids resulting from intestinal fermentation suppressing the expression level of genes involved in cholesterol biosynthesis, including HMG-CoA reductase.

Beta-conglycinin, one of the major components of soy protein, is known to decrease visceral white adipose tissue weights and liver triglyceride concentrations more effectively than intact soy protein. Additionally, β-conglycinin has been shown to increase serum adiponectin concentrations in rats. Adiponectin, one of the adipocytokines secreted by adipocytes, is known to improve lipid metabolism, enhance insulin sensitivity, and suppress blood pressure. Therefore, consuming β-conglycinin could also provide these benefits. In a feeding study using OLETF rats, an obesity model, β-conglycinin significantly decreased mesenteric adipose tissue weight and liver triglyceride concentrations, and increased insulin sensitivity compared to casein. In another feeding study using spontaneously hypertensive rats, β-conglycinin suppressed both systolic and diastolic blood pressures compared to casein. In in both cases, feeding of β-conglycinin increased plasma adiponectin concentrations. These findings suggest that β-conglycinin has multiple physiological effects and can be a beneficial food component for ameliorating metabolic syndrome.