Thyroid Issues? Low Energy Intake Triggers Low T3 / High rT3 Syndrome in Exercising Women >19kcal/kg LBM Avail. Energy Required. Low Carbing Worsens the Impact of ED
It does not take a thyroid expert to identify the reason for their problems: They are training too much and eating too little. Just like the 27 women in seminal experiment that was conducted at the Ohio University in the early 1990s. A study I am going to elaborate on in today's SuppVersity article, although I personally believe it shouldn't take experimental evidence to convince people (yes, this is true for men, as well) to stop run themselves into the ground.
Said study was conducted by Anne B. Loucks and Edward M. Heath who worked at the Derpartment of Biological Sciences and the College of Osteopathic Medicine at the Ohio University back in 1994. The purpose of their study was to characterize the functional relationship between energy availability and thyroid metabolism to gain insight into the extent of he dietary reform that might be necessary. The scientists expected to find a proportional relationship that would prove the necessity of dietary compensation for exercise energy expenditure to prevent reductions in T3 levels, scientists call "low T3 syndrome".
To this ends, Loucks & Heath recruited 28 healthy, non-obese, nonsmoking women (18-29 years old) with no recent history of dieting or weight loss were recruited from the university and surrounding community. All received a detailed verbal and written description of the study and signed an informed consent document. The participants had to keep a prospective diet records for seven consecutive days a measure that was necessary to determine their baseline energy intake and
Subjects were assigned to four groups in a monotonic experimental design of energy availability treatments.
During the first exercise bout, heart rate at 70% aerobic capacity was determined by monitoring oxygen uptake. Thereafter, heart rate was monitored continuously by means of a Uniq HeartWatch model 8799 (Computer Instruments, Hemstead, NY) and maintained at the previously measured level by adjusting treadmill speed and slope or cycle work load.
"The experimental manipulation of dietary energy intake, exercise energy expenditure, and, thereby, energy availability (defined as dietary energy intake minus energy expenditure during exercise) is shown in Fig. 1. All four experimental groups expended ~30 kcal kg LBM of energy in daily exercise at 70% of aerobic capacity for four consecutive days beginning on day 2, 3,4, or 5 of the menstrual cycle. All exercise was performed under continuous supervision on treadmill and cycle ergometers in a sequence of 30-min bouts interrupted by lo-min rest periods." (Loucks. 1994)
Figure 1: Overview of the experimental design (Loucks. 1994)
I know you will be asking, but aside from simply eating more there is no way to cure low T3 symptom. In fact the worst thing you can do is to get a script for T4 from your doc, because this will only elevate the inactive thyroid hormone (=break) rT3.If the heart rate began to drift monotonically, suggesting a thermoregulatory effect, then oxygen uptake was measured directly by gas analysis. Heart rate and Borg scores of per- ceived exertion were recorded at the fourth and fifth minutes of each exercise bout.
|Figure 2: Energy intake and expenditure (kcal/lbm) during the study period in all four grous (Loucks. 1999)|
|Table 1: Thyroid hormone concentrations before treatment and changes in concentrations resulting from 4 days of controlled energy availability | Tq, thyroxine; fT4, free T,; T3, triiodothyronine; rT3, reverse T3; ff3, free T3 (Loucks. 1999)|
- Loucks, Anne B., and Edward M. Heath. "Induction of low-T~ 3 syndrome in exercising women occurs at a threshold of energy availability." American Journal of Physiology 266 (1994): R817-R817.
- Spaulding, Stephen W., et al. "Effect of caloric restriction and dietary composition on serum T3 and reverse T3 in man." The Journal of Clinical Endocrinology & Metabolism 42.1 (1976): 197-200.