Various dietary approaches with different caloric content and macronutrient composition have been recommended to treat obesity in adults. Although their safety and efficacy profile has been assessed in numerous randomized clinical trials, reviews and meta-analyses, the characteristics of the optimal dietary weight loss strategy remain controversial. This mini-review will provide general principles and practical recommendations for the dietary management of obesity and will further explore the components of the optimal dietary intervention. To this end, various dietary plans are critically discussed, including low-fat diets, low-carbohydrate diets, high-protein diets, very low-calorie diets with meal replacements, Mediterranean diet, and diets with intermittent energy restriction. As a general principle, the optimal diet to treat obesity should be safe, efficacious, healthy and nutritionally adequate, culturally acceptable and economically affordable, and should ensure long-term compliance and maintenance of weight loss. Setting realistic goals for weight loss and pursuing a balanced dietary plan tailored to individual needs, preferences, and medical conditions, are the key principles to facilitate weight loss in obese patients and most importantly reduce their overall cardiometabolic risk and other obesity-related comorbidities.

Hydroxytyrosol (HT) is a natural antioxidant found in olive products and characterized by well-documented beneficial effects on human health. Several research studies are ongoing that aim to investigate its potency and molecular mechanism of action. The present study aimed to investigate the potential effect of HT on human obesity through a randomized double-blind prospective design. HT in two different doses (15 and 5 mg/day) and a placebo capsule was administered to 29 women with overweight/obesity for six months and their weight and fat mass were monitored at three time points (baseline, 4, 12 and 24 weeks). Statistically significant weight and visceral fat mass loss (%weight loss: p = 0.012, %visceral fat loss: p = 0.006) were observed in the group receiving the maximum HT dosage versus placebo after 4 weeks of the intervention, with attenuation of these findings at 12 and 24 weeks of the study. Urine samples were collected during the intervention and analyzed via liquid chromatography–high-resolution mass spectrometry for untargeted metabolomic purposes and comparisons between study groups were performed. HT administration was safe and well-tolerated. To the best of our knowledge, this is the first human cohort investigating the effects of HT on obesity for a prolonged study period.

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a member of the TNF protein superfamily, represents a multifaceted cytokine with unique biological features including both proapoptotic and pro-survival effects in different cell types depending on receptor interactions and local stimuli. Beyond its extensively studied anti-tumor and immunomodulatory properties, a growing body of experimental and clinical evidence over the past two decades suggests a protective role of TRAIL in the development of type 1 (T1DM) and type 2 (T2DM) diabetes mellitus. This evidence can be briefly summarized by the following observations: (i) acceleration and exacerbation of T1DM and T2DM by TRAIL blockade or genetic deficiency in animal models, (ii) prevention and amelioration of T1DM and T2DM with recombinant TRAIL treatment or systemic TRAIL gene delivery in animal models, (iii) significantly reduced circulating soluble TRAIL levels in patients with T1DM and T2DM both at disease onset and in more advanced stages of diabetes-related complications such as cardiovascular disease and diabetic nephropathy, (iv) increase of serum TRAIL levels in diabetic patients after initiation of antidiabetic treatment and metabolic improvement. To explore the underlying mechanisms and provide mechanistic links between TRAIL and diabetes, a number of animal and in vitro studies have reported direct effects of TRAIL on several tissues involved in diabetes pathophysiology such as pancreatic islets, skeletal muscle, adipose tissue, liver, kidney, and immune and vascular cells. Residual controversy remains regarding the effects of TRAIL on adipose tissue homeostasis. Although the existing evidence is encouraging and paves the way for investigating TRAIL-related interventions in diabetic patients with cardiometabolic abnormalities, caution is warranted in the extrapolation of animal and in vitro data to the clinical setting, and further research in humans is imperative in order to uncover all aspects of the TRAIL-diabetes relationship and delineate its therapeutic implications in metabolic disease.

Diabetes mellitus is usually preceded by a pre-diabetic stage before the clinical presentation of the disease, the influence of which on persons’ quality of life is not adequately elucidated. The purpose of this study was to compare the Health-Related Quality of Life (HRQOL) of persons with pre-diabetes with that of diabetes or normal glucose tolerance (NGT), using the validated HRQOL-15D questionnaire. The HRQOL-15D scores of 172 people with pre-diabetes (108 with Impaired Fasting Glucose [IFG], 64 with Impaired Glucose Tolerance [IGT], aged 58.3 ± 10.3 years) and 198 with NGT (aged 54.4 ± 10.1 years) from the Greek part of the DEPLAN study (Diabetes in Europe - Prevention using Lifestyle, Physical Activity and Nutritional Intervention), were compared to 100 diabetes patients’ scores (aged 60.9 ± 12.5 years, diabetes duration 17.0 ± 10.0 years, HbA1c 7.2 ± 1.2%), derived from the outpatient Diabetes Clinic of a University Hospital. The diabetes patients’ HRQOL-15D score (0.8605) was significantly lower than the pre-diabetes’ (0.9008) and the controls’ (0.9092) (p < 0.001). There were no differences in the total score between the controls and the group with pre-diabetes. However, examination of individual parameters of the score showed that people with IGT had lower scores compared to the control group, as related to the parameters of “mobility” and “psychological distress”. No differences were found in any component of the HRQOL-15D score between the control group and the IFG group, nor between the two groups with pre-diabetes (IFG vs. IGT). Persons with pre-diabetes had a similar HRQOL score with healthy individuals, and a higher score than persons with diabetes. Specific components of the score, however, were lower in the IGT group compared to the controls. These findings help clarify the issue of HRQOL of persons with pre-diabetes and its possible impact on prevention.

Irisin is a myokine that increases energy expenditure. In this cross-sectional study, we examined for differences in plasma irisin concentrations between subjects with type 1 diabetes mellitus and healthy individuals and searched for associations between plasma irisin levels and clinical and biochemical characteristics as well as self-reported physical activity. A total of 79 subjects with type 1 diabetes [age 38.2±12.5 years, men/women (n): 27/52], were consecutively recruited. Moreover, 53 healthy controls, matched for age and body mass index with those with diabetes were recruited. Plasma irisin was measured with ELISA. Participants were asked about their physical activity during the last week. We also measured trunk and visceral fat. Circulating irisin levels were lower in subjects with diabetes than in controls [median value (interquartile range): 53.0 (35.2, 106.3) vs. 178.1 (42.6, 641.6) ng/ml, respectively, p<0.001]. In the group of diabetes, univariate analysis showed that irisin levels were associated with waist circumference (beta=–0.283, p=0.023), serum triglycerides (beta=–0.282, p=0.031), and trunk fat (beta=–0.324, p=0.012). In multivariate analysis after adjustment for potential confounders, irisin levels were associated independently only with waist circumference (beta=–0.403, p=0.005). Among controls, multivariate analysis demonstrated that irisin levels were associated with pack-years of smoking (beta=–0.563, p=0.012) and fasting triglycerides (beta=–0.338, p=0.041). Circulating irisin levels were lower in subjects with diabetes in comparison with healthy-matched controls. In conclusion, plasma irisin concentrations in subjects with diabetes were associated with waist circumference, while in controls with serum triglycerides and pack-years of smoking.