Are menstrual disturbances associated with an energy availability threshold? A critical review of the evidence.

Exercising women have a high prevalence of menstrual disturbances. In 2003, it was suggested that disruption in luteinizing hormone (LH) pulsatility occurs below a threshold of energy availability (EA) of 30 kcal/kg lean body mass (LBM)/day. This paper is a critical review of the evidence regarding the theory that disruptions to the reproductive axis and menstrual disturbances occur below the proposed threshold. Short-term laboratory studies demonstrated that 4-5 days of an EA below 30 kcal/kg LBM/day, induced with or without exercise, decreased serum triiodothyronine and LH pulse frequency, and increased LH pulse amplitude in sedentary, regularly menstruating women. Fewer studies have investigated downstream ovarian effects after long-term exposure to low EA. The Sargent Camp Study was the first randomized trial that induced luteal phase defects, delayed menses, and anovulation by causing weight loss (-4 ± 0.3 kg) with an abrupt increase in exercise volume for two menstrual cycles. The BioEnergetics Study was a randomized controlled trial that induced varying levels of energy deficits by manipulating energy intake and expenditure for three menstrual cycles. LH pulse frequency and triiodothyronine decreased, and 57% of women developed luteal phase defects, anovulation, and/or oligomenorrhea. An EA below 30 kcal/kg fat free mass/day increased the chance of experiencing a menstrual disturbance by 50%. However, menstrual disturbances were observed above and below that EA threshold, and changes in LH pulse frequency predicted only luteal phase defects, not oligomenorrhea or anovulation. The proposed EA threshold is not a cut-off below which menstrual disturbances occur, but represents an increased risk of experiencing menstrual disturbances.

Mathematical Model for Body Fat Percentage in Military using Thermal Imaging and Circumferences.

The prevalence of overweight and obesity has gradually increased throughout the world. In this sense, body composition evaluation' methods have gained special attention in some research areas. The aim of this study was to propose a mathematical model to estimate body fat percentage (BF%) of men from thermal imaging and body circumferences variables and using as gold standard values obtained by Dual-Energy XRay Absorptiometry (DXA). This was a cross-sectional study. A Sample of 47 men aged from 18 to 20 years was involved in the study. They were selected among soldiers from Brazilian Army. Data collection was carried out in just one day, in the following sequence: thermal imaging, body fat percentage assessed by DXA and anthropometric measures. It was performed the identification of the skin temperature strongest correlated with BF% in each body segment (trunk, upper and lower limbs). The same procedure was done with anthropometrics variables. After that, these variables were tested in the linear regression model. Waist, abdomen and hip circumferences, as expected, showed strong positive correlations with BF% (r = 0.826, 0.873, and 0.853, respectively). Since the skin temperature values tended to negative correlation with BF%, the best results were found for mean skin temperature of the anterior face of the trunk (r = -0 753) and posterior face (r = -0723). The best model reaches an R square of 0.800 using just one anthropometric and one skin temperature variable (BF% =32.34 + (0.6 x AC) - (1.87 x ATSkTMean)), where AC means abdominal circumference and ATSkTMean means the mean skin temperature from the anterior face of the trunk. The proposed model can be used by Brazilian Army to estimate BF% of soldiers and male military personal aged from 18 to 20 years.