In overweight or obese patients with type 2 diabetes, a short-term (21 days) nutritional intervention trial using 2 different diets showed that both diets resulted in beneficial effects on metabolic parameters. The macrobiotic Ma-Pi 2 diet was associated with a greater reduction in fasting and post prandial plasma glucose, HbA1c, serum cholesterol, HOMA-IR, BMI, and waist and hip circumferences than the standard control diet.
Our study is the first randomized trial to assess and quantify the reported beneficial effects of the Ma-Pi 2 diet versus the standard nutritional recommendations for type 2 diabetes . In this trial patients consuming the Ma-Pi 2 diet experienced a statistically significantly greater benefit in terms of reduced FBG, PPBG, HbA1c, and HOMA–IR, compared to patients receiving the control diet, suggesting that the Ma-Pi 2 macrobiotic diet is a more effective dietary intervention than the standard recommended diet for improving metabolic control in patients with type 2 diabetes. Also, significantly greater weight loss was obtained in the Ma-Pi 2 diet group compared with the control group, despite consumption of the same energy content in both diets. The Ma-Pi 2 diet was also higher in fiber content by up to 10 g/1000 kcal (50%) than the control diet which may also have contributed to the greater weight loss in the Ma-Pi 2 diet group; Langlois et al. conducted a retrospective cohort study of the Canadian population and found that dietary fiber intake was inversely related with incidence of obesity .
A reduction in total cholesterol, LDLc and LDL/HDL ratio was observed with both diets, but was significantly higher with the Ma-Pi 2 diet. This could be the result of a higher intake of wholegrain cereals; this is in line with a Cochrane review on the effect of wholegrain cereals on coronary heart disease that found that short-term dietary oatmeal intervention was associated with lower total cholesterol and LDLc .
The success of the control diet in improving metabolic control is supported by previous studies on Mediterranean diets. A systematic review and meta-analysis found significant improvement in glycemic control in low-carbohydrate, Mediterranean, and high-protein diets and a greater weight loss in low-carbohydrate and Mediterranean diets compared with their respective control diets ; A short trial on the effect of a high-protein/low-carbohydrate diet on glucose control showed a reduction in circulating glucose concentration in patients with untreated type 2 diabetes ; A Mediterranean diet, rich in monounsaturated fatty acids and in complex carbohydrate but not high in protein was associated with lower HbA1c levels and 2 hour post-meal glucose levels independently of variations in age, adiposity, energy intake, and physical activity in 901 patients with type 2 diabetes .
Overall the positive results obtained with the two diets in our short-term study may be explained in part by the wellbeing (emotional and physical) state of our patients since they were located close to the sea, had a strict control on the caloric intake, perform regular (monitored) physical activity improving their overall quality of life. The greater effect of the Ma-Pi 2 diet compared to the control diet on a number of metabolic parameters may be due to several factors, from changes in inflammation and/or oxidative stress  to the composition of microbiota . Ongoing studies should elucidate all these issues, hence a long-term sustainability of the Ma-Pi 2 diet, in particular the acceptance and adherence of the patient to the diet, the implying costs in the patient management remain to be proven.
Patient compliance and adherence to recommended therapeutic diets for diabetes are essential for the diets to be able to produce clinically-significant improvements in patient outcomes, and positive results achieved with diets in clinical trials are often difficult to replicate in real-life practice . In the study presented here, participants attended 2-hour meetings daily for nutritional education and cooking instructions in their respective hotels conducted by a physician and a registered dietitian and/or a cooking instructor. This was done to encourage continuation of the respective diets once the trial was completed.
Our study had a number of limitations including short duration, lack of blinding, and relatively small sample size. The short duration was due to the difficulty in accommodating participants for 24 hours per day and requiring them not to leave their respective hotels for the duration of the trial. A longer-term trial of this type is unlikely to be successful due to the lower number of volunteers and higher number of dropouts that would be likely with increased duration. Participant blinding was impossible due to the distinct differences in the ingredients and therefore taste and appearance of the 2 diets used. Similarly, it was also not possible to blind the medical staff present at the hotels. However, the investigators involved in follow-up and blood testing were blinded to the treatment groups.