180. The Truth About Cortisol, Insulin & Overtraining | Shawn Arent, PhD, CSCS

We are back with a powerhouse guest, Dr. Shawn Arent, for part 1 of a series on hormone optimization. From cortisol misconceptions to insulin fearmongering, they cut through the noise with science-backed insight into performance, recovery, and stress physiology. You’ll rethink everything you’ve seen on social media about hormones.

TIMESTAMPS

00:00 Introduction to Medicine Redefined

00:36 Welcoming Dr. Sean Art

02:11 The Importance of Cortisol

02:49 Understanding Cortisol's Role in Performance

04:59 Chronic Cortisol and Overtraining

13:51 Monitoring Stress and Performance

22:30 The Role of Nutrition in Cortisol Management

33:31 Insulin: The Anabolic Hormone

39:27 Exercise and Insulin Sensitivity

40:43 Impact of Stress and Sleep on Glucose Levels

43:02 Continuous Glucose Monitors: Pros and Cons

47:42 Athlete Nutrition and Performance

55:52 Hormonal Responses to Training

01:07:18 Sex Hormones and Athletic Performance

01:17:37 Conclusion and Future Topics

SOURCES

00:00:22 | Cortisol deficiency (Addison’s disease) is life-threatening

00:04:42 | Cortisol peaks in early morning (chronobiology) 

00:05:25 | Acute sleep deprivation significantly increases cortisol 

00:05:42 | One week of 5h/night sleep restriction lowers testosterone by \~10–15% 

00:22:11 | Cortisol stimulates gluconeogenesis (maintains blood glucose upon waking) 

00:27:38 | No single reliable biomarker for overtraining syndrome 

00:27:38 | Overtrained athletes show blunted HR, blood lactate and cortisol responses 

00:29:00 | Prolactin rises in response to stress/exercise 

00:30:00 | Dietary fat guidelines: 20–35% of calories from fat 

00:33:30 | Insulin is an anabolic hormone promoting nutrient storage 

00:33:30 | Low-fat (∼20% fat) diets reduce testosterone 10–15% vs high-fat diets 

00:39:26 | Regular exercise improves insulin sensitivity 

00:39:26 | ~38% (~98M) of U.S. adults have prediabetes 

00:40:29 | Shorter sleep duration impairs insulin sensitivity 

00:01:02:57 | Exercise above the lactate threshold elicits maximal GH release

01:04:42 | Resting lactate \~1–2 mmol/L; intense exercise >20 mmol/L 

01:08:53 | Higher testosterone levels correlate with greater lean mass in men 

01:11:51 | Winners in competition show post-event testosterone spikes 

01:12:29 | Female athlete amenorrhea leads to low bone density and stress fractures

01:12:29 | Amenorrheic female athletes have lower IGF-1 (growth factor) 

01:08:53 | Testosterone even within normal range affects strength/mass