Dietary patterns predict changes in two-hour post-oral glucose tolerance test plasma glucose concentrations in middle-aged adults

Dietary patterns: a literature review of the methodological characteristics of the main step of the multivariate analyzes

OBJECTIVE

To describe the solutions adopted in the multiple steps of the use of multivariate techniques to obtain a dietary pattern (DP) concerning: the objective of the studies, the selection of the method for measuring food intake, the criteria for grouping the foods, the number of food groups used, the number of DP obtained, and the nomenclature criteria.

METHODS

The articles were selected from MEDLINE and Lilacs scientific databases using the following keywords: "dietary patterns" versus "factor analysis"; "principal components analysis"; "cluster analysis" and "reduced regression rank." The initial search resulted in 1,752 articles. After inclusion and exclusion criteria, 189 publications were selected.

RESULTS

The following aspects were relevant among the studies: the prevalence of the principal component analysis (PCA); the prevalence of the use of 4 to 5 DPs in the studies of association with health outcomes; the use of 30 or more food groups from the food frequency questionnaire (FFQ); the prevalence of studies that associated DPs with health outcomes and socioeconomic factors; and the heterogeneity of criteria used throughout the analytical stages of the multivariate techniques.

CONCLUSION

The heterogeneity between the publications concentrates on the criteria for food grouping, the nomenclature, and the number of dietary patterns calculated, which varied depending on the number of food groups present in these analyses. To understand, apply, and explore in full, the multivariate techniques has become necessary in order to improve the reliability of the results and, consequently, to improve the relationships with health outcomes and socioeconomic factors.

Prediabetes Phenotype Influences Improvements in Glucose Homeostasis with Resistance Training

Purpose

To determine if prediabetes phenotype influences improvements in glucose homeostasis with resistance training (RT).

Methods

Older, overweight individuals with prediabetes (n = 159; aged 60±5 yrs; BMI 33±4 kg/m²) completed a supervised RT program twice per week for 12 weeks. Body weight and composition, strength, fasting plasma glucose, 2-hr oral glucose tolerance, and Matsuda-Defronza estimated insulin sensitivity index (ISI) were assessed before and after the intervention. Participants were categorized according to their baseline prediabetes phenotype as impaired fasting glucose only (IFG) (n = 73), impaired glucose tolerance only (IGT) (n = 21), or combined IFG and IGT (IFG/IGT) (n = 65).

Results

Chest press and leg press strength increased 27% and 18%, respectively, following the 12-week RT program (both p<0.05). Waist circumference (-1.0%; pre 109.3±10.3 cm, post 108.2±10.6 cm) and body fat (-0.6%; pre 43.7±6.8%, post 43.1±6.8%) declined, and lean body mass (+1.3%; pre 52.0±10.4 kg, post 52.7±10.7 kg) increased following the intervention. Fasting glucose concentrations did not change (p>0.05) following the intervention. However, 2-hr oral glucose tolerance improved in those with IGT (pre 8.94±0.72 mmol/l, post 7.83±1.11 mmol/l, p<0.05) and IFG/IGT (pre 9.66±1.11mmol/l, post 8.60±2.00 mmol/l) but not in those with IFG (pre 6.27±1.28mmol/l, post 6.33± 1.55 mmol/l). There were no significant changes in ISI or glucose area under the curve following the RT program.

Conclusions

RT without dietary intervention improves 2-hr oral glucose tolerance in individuals with prediabetes. However, the improvements in glucose homeostasis with RT appear limited to those with IGT or combined IFG and IGT.

Trial Registration

ClinicalTrials.gov: NCT01112709

Dietary patterns, risk and prognosis of breast cancer

Survival in women diagnosed with early-stage, invasive breast cancer has improved dramatically in the past 10–15 years. This is largely due to the use of pharmacological therapies targeting a reduction in estrogen action and exposure. Women diagnosed with breast cancer often alter their eating behavior towards healthier food choices in an attempt to improve their survival and their overall health and well being. Mounting interest in the role of diet to modify breast cancer survival and/or comorbidity and mortality has led researchers to evaluate the effects of differential dietary patterns on this disease. Current findings suggest a possible, but inconsistent, benefit of a prudent, vegetable-rich, low-fat/high-vegetable eating pattern on disease-free survival, but the results to date are limited by strong treatment effectiveness and low overall recurrence rates. It is more likely this prudent eating pattern will improve non-breast cancer mortality (e.g., cardiovascular disease) compared with a Western dietary pattern. Efforts to educate women diagnosed with breast cancer to consume a diet lower in total and saturated fat, higher in vegetables and fiber, and which results in mild to modest weight loss among overweight/obese women is sensible in light of the high survivability of breast cancer and need to direct attention to comorbidities that likely increase as a consequence of treatment and treatment-related weight gain and sedentary behavior. Additional research is needed to address the importance of diet in the breast cancer patient, particularly in relation to the effect of select dietary patterns on factors that influence individual recurrence risk (e.g., hormone levels, drug metabolism and oxidative stress), as well as factors that influence non-breast cancer morbidity risk and causes of death in the survivor population.

Pathophysiology and aetiology of impaired fasting glycaemia and impaired glucose tolerance: does it matter for prevention and treatment of type 2 diabetes?

Prior to the development of type 2 diabetes, glucose levels increase into the prediabetic states of isolated impaired fasting glycaemia (i-IFG), isolated impaired glucose tolerance (i-IGT), or combined IFG/IGT. A better understanding of the aetiology and pathophysiology of the prediabetic states might give a basis for the development of individualised prevention and treatment strategies for type 2 diabetes. Several studies have examined mechanisms and potential aetiological factors leading to the development of the different prediabetic states. The pathophysiology of i-IFG seems to include the following key defects: reduced hepatic insulin sensitivity, stationary beta cell dysfunction and/or chronic low beta cell mass, altered glucagon-like peptide-1 secretion and inappropriately elevated glucagon secretion. Conversely, the prediabetic state i-IGT is characterised by reduced peripheral insulin sensitivity, near-normal hepatic insulin sensitivity, progressive loss of beta cell function, reduced secretion of glucose-dependent insulinotropic polypeptide and inappropriately elevated glucagon secretion. Individuals developing combined IFG/IGT exhibit severe defects in both peripheral and hepatic insulin sensitivity as well as a progressive loss of beta cell function. The aetiologies of i-IFG and i-IGT also seem to differ, with i-IFG being predominantly related to genetic factors, smoking and male sex, while i-IGT is predominantly related to physical inactivity, unhealthy diet and short stature. Since the transition from the prediabetic states to overt type 2 diabetes is characterised by a non-reversible vicious cycle that includes severe deleterious effects on glucose metabolism, there are good reasons to use the well-established aetiological and pathophysiological differences in i-IFG, i-IGT and IFG/IGT to design individualised preventive strategies.