In this conversation, Simon and Brian discuss their recent race experiences and the challenges they faced with heat and altitude. They invite Alex Larson, a registered dietitian, to provide tips on nutrition and hydration for endurance athletes. Alex shares insights on fueling for summer race conditions, managing hydration in hot and humid environments, and the importance of electrolyte balance. She also discusses the individual variability in sweat rates and offers recommendations for determining hydration needs. The conversation highlights the significance of proper nutrition and hydration in optimizing performance and preventing dehydration and GI issues. The conversation covered various topics related to nutrition and hydration for endurance athletes. They discussed the importance of testing for sweat rate and sodium loss, the difference between calories and grams of carbs, the challenges of nutrition and hydration at high altitude and in high humidity, the impact of intermittent fasting on performance and recovery, and the approach to body composition for endurance athletes. The guest, Alex Larson, provided valuable insights and recommendations throughout the conversation.