Specific medical examinations and health guidance to prevent and/or improve metabolic syndrome have been implemented by insurers in Japan since 2008 to stem the increase in lifestyle-related diseases. However, the objectives of reducing health care costs, reducing abdominal obesity, and preventing metabolic syndrome have not yet been realized. The Healthy Japan 21 advocated by the Japanese Ministry of Health, Labour and Welfare (2000) recommends that adults ingest ≥ 350 g of vegetables per day. Therefore, changes in food consumption patterns and environment must be incorporated into primary countermeasures against lifestyle-related diseases. Thus, we provided a Japanese-style healthy lunch menu daily for 3 months at a workplace cafeteria to examine the ability of consumption of this style of meal to prevent and/or improve metabolic syndrome.
The intervention group displayed reduced blood pressure and serum lipid markers after 3 months compared with the baseline. These improvements were observed particularly in cases where the intake frequency of the Japanese-style healthy lunch was high. Furthermore, plasma active ghrelin and desacyl ghrelin levels, which are related to appetite, increased compared with the baseline. These results mainly seem attributable to increased vegetable intake. In contrast with the intervention group, the control group showed unchanged biochemical markers and anthropometric data throughout the time frame of the study. Hung et al. reported that high fruit and vegetable intake helps to modestly reduce the risk of major chronic disease, and their findings support the recommendation of consuming at least five daily servings of fruits and vegetables. Increasing fruit and vegetable intake appears to confer a benefit primarily of a lower risk of CVD but not of cancer. The effect of the present intervention on cancer prevention is uncertain.
However, an increase in dietary fiber and vitamins could partly explain the lower blood pressure and decreased serum lipid markers observed in the intervention group. Fiber is a dietary factor that has received substantial attention[17, 18]. Burton-Freeman reported that dietary fiber functions as an energy intake regulator. Furthermore, the contents of the provided healthy lunches support the claim that the intervention group had an increase in total and soluble dietary fiber intake after compared with before the intervention. Liu et al. suggested that higher intake of fruits and vegetables can protect against CVD, and their findings support current dietary guidelines that promote increased fruit and vegetable intake. They also reported that higher intake of dark yellow and green leafy vegetables can help to prevent type 2 diabetes among overweight women.
In addition, we surmised that a high-fiber diet increases the amount of mastication. Yamazaki et al. reported that higher masticatory performance and eating slowly helps prevent diabetes. Their results imply that higher mastication can decrease blood glucose and HbA1C levels. However, the present study did not find any changes in related blood parameters. We believe that blood parameters can be improved by lengthening the period of intervention and increasing the frequency with which individuals choose the foods offered on healthy menus.
In the intervention group, plasma active ghrelin and desacyl ghrelin levels significantly increased after 3 months compared with the baseline.
Ghrelin is an orexigenic hormone predominantly secreted by the stomach and stimulates appetite and food intake after i.v. administration. The postprandial ghrelin response depends on the nutrient composition of ingested meals, and several studies support the notion that elevated postprandial and later interdigestive ghrelin levels could contribute to recurrent hunger pangs and appetite. Ghrelin is a somatotropic and orexigenic hormone that functions as an important energy metabolism regulator and a physiological regulator of insulinemia and glycemia. Some studies have shown that circulating plasma ghrelin levels are lower in obese children and adults than in age-matched lean control individuals[24, 25]. Plasma ghrelin levels increase in individuals with a negative energy balance such as those on a low-energy diet or anti-obesity medication, or in those who exercise regularly[26, 27]. Furthermore, plasma ghrelin might play a role in energy balance.
Horigome notably reported significant associations among hemostatic parameters, adipokines, and metabolic syndrome components among Japanese preschool children. Children with BMI of ≥90%ile had significantly higher SBP and heart rates and higher blood levels of insulin and leptin. They also showed higher insulin resistance by the homeostasis model assessment and lower desacyl ghrelin levels than children with BMI of <90% ile.
Pöykkö and Fagerberg described that ghrelin concentrations were negatively associated with fasting insulin and systolic and diastolic blood pressure in the multivariate models[29, 30]. SBP/DBP in the present study was significantly reduced after 3 months compared with the baseline.
Furthermore, serum leptin levels after 3 months were significantly reduced compared with the baseline in the intervention group. Particularly in the Japanese-style healthy lunch menu intake frequency ≥ 50%ile group, BFP after 3 months significantly decreased compared with the baseline. Leptin, which is produced by adipose tissue, reduces food intake while increasing energy expenditure and positively correlates with fat mass[31, 32]. Elevated leptin levels are independently correlated with increased CVD risk[33, 34]. Reduced leptin levels while fasting during weight loss can be attributed to decreased leptin resistance. The relatively short duration of the intervention could explain the finding that BFP and serum leptin levels decreased in the present study. In the control group, no statistically significant differences in active ghrelin, desacyl ghrelin, and leptin concentrations between baseline and after 3 months were observed. It is unknown clinically. We believe that inspection by long-term intervention in a randomized clinical trial is necessary in future to determine the effect of ghrelin and leptin concentrations.
We believe that these findings will contribute to epoch-making metabolic syndrome prevention and improvement. However, this study is limited by its structure as a small non-randomized controlled trial. Hence, we plan to implement an additional intervention study with an increased number of participants.