IMO 37 - Losing Weight to Run Faster Updates, Dynafish Going Crazy In China and Attempting The Marathon World Record in Jeans

Welcome back to another unstructured In My Opinion episode. Matt shares an update on losing weight to run faster, the explosion of Chinese super shoes and Dynafish, a potential marathon world record attempt in jeans, HYROX plans, coaching updates and why he has backed away from frequent sauna use.
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Matt opens with updates on the Sweat Elite Podcast, including changes to the private feed, a new weekly subscriber hangout and a small number of coaching opportunities becoming available.
The main discussion centres around losing weight to run faster, prompted partly by Josh Kerr's visible change in body composition alongside his recent performances. Matt reflects on his own marathon career, including a period where gaining roughly 3.5 kg coincided with slower marathon performances before intentionally losing around 4 kg and returning to consistent sub-2:20 racing.
Matt explains the simple approach he has personally used - maintaining a modest calorie deficit on most days while prioritising high-volume, satiating foods, then aggressively increasing carbohydrate intake around important training. Rather than trying to remain perfectly fuelled every hour of every day, he discusses using roughly 12-hour windows before major sessions and races to maximise carbohydrate availability, followed by substantial refuelling afterwards.
He also discusses why he avoids obsessing over daily scale weight, instead looking at longer-term trends and carbohydrate cycles. Matt believes intentional weight-loss phases should generally be relatively short - around 6 to 12 weeks for most athletes and rarely beyond 20 weeks - rather than becoming a permanent part of training.
The conversation also tackles the stigma surrounding weight loss in endurance sport, RED-S, disordered eating and the potential danger of becoming obsessed with numbers. Matt stresses that this approach is only relevant to runners who genuinely have weight they can healthily lose and that improving performance should never come at the expense of long-term health.
Later in the episode, Matt shares updates from the Chinese running shoe world, including upcoming laboratory testing of several Chinese super shoes and the rapid growth surrounding Dynafish. He discusses distribution delays, demand in China and plans for bringing more shoes into international markets.
Matt also considers racing the Sydney Marathon in jeans and potentially attempting the marathon world record for running in jeans, before discussing his future racing ambitions, interest in trying HYROX and whether an Ironman is something he would ever consider.
Finally, Matt explains why he has stopped frequent sauna sessions after noticing increasing fatigue and deteriorating training quality, despite initially introducing sauna as part of his marathon preparation.
Topics:
00:00 Welcome and Setup
00:27 Topics and Context
02:46 Pro Podcast Changes
03:46 Subscriber Hangouts
06:05 Coaching Spots Open
07:12 Why Weight Matters
08:18 Josh Kerr Example
09:45 My Marathon Weight Shift
14:41 Stigma and Pushback
20:08 Simple Weight Loss Framework
24:34 Carb Timing for Workouts
28:59 Risks and Obsession Trap
30:38 Carb Cycles Not Scales
31:44 Avoid Number Obsession
32:47 Who Should Cut Weight
35:46 Coaching And Stigma
37:36 Chinese Shoe Lab Tests
39:39 Dynafish Distribution Plans
43:36 Sydney Jeans Marathon
45:40 Weight Loss And Future Goals
50:55 HYROX Versus Ironman
52:31 Sauna Fatigue Lesson
57:25 Wrap Up And Next Steps