Metabolic syndrome (MetS) is established as the combination of central obesity and different metabolic disturbances, such as insulin resistance, hypertension and dyslipidemia. This cluster of factors affects approximately 10%–50% of adults worldwide and the prevalence has been increasing in epidemic proportions over the last years. Thus, dietary strategies to treat this heterogenic disease are under continuous study. In this sense, diets based on negative-energy-balance, the Mediterranean dietary pattern, n-3 fatty acids, total antioxidant capacity and meal frequency have been suggested as effective approaches to treat MetS. Furthermore, the type and percentage of carbohydrates, the glycemic index or glycemic load, and dietary fiber content are some of the most relevant aspects related to insulin resistance and impaired glucose tolerance, which are important co-morbidities of MetS. Finally, new studies focused on the molecular action of specific nutritional bioactive compounds with positive effects on the MetS are currently an objective of scientific research worldwide. The present review summarizes some of the most relevant dietary approaches and bioactive compounds employed in the treatment of the MetS to date.

Irisin is assumed to be a relevant link between muscle and weight maintenance as well as to mediate exercise benefits on health. The aim of this study was to assess the possible associations between irisin levels and glucose homeostasis in obese subjects with metabolic syndrome (MetS) following an energy-restricted treatment. Ninety-six adults with excessive body weight and MetS features underwent a hypocaloric dietary pattern for 8 weeks, within the RESMENA randomized controlled trial (www.clinicaltrials.gov; NCT01087086). After the intervention, dietary restriction significantly reduced body weight and evidenced a dietary-induced decrease in circulating levels of irisin in parallel with improvements on glucose homeostasis markers. Interestingly, participants with higher irisin values at baseline (above the median) showed a greater reduction on glucose (P=0.022) and insulin (P=0.021) concentrations as well as on the homeostasis model assessment index (P=0.008) and triglycerides (P=0.006) after the dietary intervention, compared with those presenting low-irisin baseline values (below the median). Interestingly, a positive correlation between irisin and carbohydrate intake was found at the end of the experimental period. In conclusion, irisin appears to be involved in glucose metabolism regulation after a dietary-induced weight loss.

The long-term effects of dietary strategies designed to combat the metabolic syndrome (MetS) remain unknown. The present study evaluated the effectiveness of a new dietary strategy based on macronutrient distribution, antioxidant capacity and meal frequency (MEtabolic Syndrome REduction in NAvarra (RESMENA) diet) for the treatment of the MetS when compared with the American Heart Association guidelines, used as Control. Subjects with the MetS (fifty-two men and forty-one women, age 49 (se1) years, BMI 36·11 (se0·5) kg/m²) were randomly assigned to one of two dietary groups. After a 2-month nutritional-learning intervention period, during which a nutritional assessment was made for the participants every 15 d, a 4-month self-control period began. No significant differences were found between the groups concerning anthropometry, but only the RESMENA group exhibited a significant decrease in body weight ( − 1·7 %;P= 0·018), BMI ( − 1·7 %;P= 0·019), waist circumference ( − 1·8 %;P= 0·021), waist:hip ratio ( − 1·4 %;P= 0·035) and android fat mass ( − 6·9 %;P= 0·008). The RESMENA group exhibited a significant decrease in alanine aminotransferase and aspartate aminotransferase (AST) concentrations ( − 26·8 %;P= 0·008 and − 14·0 %;P= 0·018, respectively), while the Control group exhibited a significant increase in glucose (7·9 %;P= 0·011), AST (11·3 %;P= 0·045) and uric acid (9·0 %;P< 0·001) concentrations. LDL-cholesterol (LDL-C) concentrations were increased (Control group: 34·4 %;P< 0·001 and RESMENA group: 33·8 %;P< 0·001), but interestingly so were the LDL-C:apoB ratio (Control group: 28·7 %;P< 0·001, RESMENA group: 17·1 %;P= 0·009) and HDL-cholesterol concentrations (Control group: 21·1 %;P< 0·001, RESMENA group: 8·7;P= 0·001). Fibre was the dietary component that most contributed to the improvement of anthropometry, while body-weight loss explained changes in some biochemical markers. In conclusion, the RESMENA diet is a good long-term dietary treatment for the MetS.