Matt is joined by Dr David Lipman to discuss one of the newest and most talked-about supplements emerging in elite endurance sport: lactate gels.

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The conversation has gained attention around the Tour de France, with companies including From Lab to Field, Enervit and Santa Madre developing lactate-based products. Unlike glucose and fructose, which rely primarily on SGLT1 and GLUT5 transporters in the gut, lactate uses monocarboxylate transporters (MCTs). This potentially provides athletes with another pathway to absorb and utilise energy alongside traditional carbohydrate fueling.

The concept isn't completely new, but delivering meaningful amounts of lactate without creating gastrointestinal or taste problems has historically been difficult. From Lab to Field is developing a patented hydrogel designed to improve lactate delivery and tolerance while producing a less acidic product. Early prototypes have reportedly combined around 5 g of lactate with 40 g of carbohydrate.

There are also interesting possibilities beyond simply providing additional energy. Lactate can be used as fuel by the muscles, heart and brain and also acts as a signalling molecule. Researchers are investigating whether supplementation could influence glycogen replenishment, recovery and metabolic responses during exercise.

There are already some impressive performance claims circulating, including improvements in power output and reductions in fatigue, but the evidence remains preliminary. Much of the exciting data appears to come from research connected to the companies developing the products and still needs independent replication.

One particularly interesting possibility is that lactate supplementation may have different effects below versus above the first lactate threshold. Elite athletes reportedly using lactate alongside very high carbohydrate intakes of around 90-120+ g/h have described positive experiences, but exactly how much additional benefit lactate provides remains uncertain.

The discussion also compares lactate with exogenous ketones, another alternative fuel that has generated significant interest in endurance sport. Ketones have produced mixed performance results, although emerging research suggests potential benefits in areas such as heat tolerance, recovery, altitude exposure, sleep and resilience to heavy training.

Both lactate and ketones may eventually have applications outside sport because of their roles as fuels and signalling molecules, particularly in the brain. Overall, lactate gels represent an exciting new area of endurance nutrition, but they're still at the beginning of the research cycle. The potential is significant, but athletes should distinguish promising early findings from benefits that have been independently and consistently demonstrated.

Episode Chapters:

00:00 Lactate Gel Buzz
00:19 Who's Making Them
01:16 How Lactate Fuels
02:53 Hydrogel Delivery Breakthrough
03:58 Legality and Doping Questions
05:20 Performance Claims and Evidence
06:42 Real World Use and Cost
07:43 Beyond Sport Applications
08:56 Ketones Update and Research
11:25 Personal Ketone Use Cases
12:44 Conflicts and Wrap Up

Jordan Sullivan, The Fight Dietitian, joins Matt to break down performance-focused weight loss, RED-S, marathon fueling and how endurance athletes can get lighter without sacrificing training quality.

Jordan Sullivan / The Fight Dietitian

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Matt Fox / Sweat Elite

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In this episode, Jordan and Matt dive into one of the most debated topics in endurance sport - losing weight while training hard. Jordan has spent more than a decade working with elite athletes across combat sports, endurance events and other high-performance environments, helping athletes manipulate body composition while maintaining performance.

They discuss RED-S, low energy availability and why the intensity and duration of a calorie deficit matter. Jordan explains why training status is an important part of the equation, how quickly athletes can realistically lose weight, and why Garmin, WHOOP and other wearable calorie estimates should not be treated as exact measurements.

They also explore what happens to muscle during a calorie deficit, the roles of protein and resistance training, and what changes when an already-lean athlete tries to become even lighter. Jordan and Matt discuss Matt's own progression from around 74 kg toward 69 kg, and the longer-term possibility of experimenting closer to 65 kg while trying to determine where further weight loss stops improving marathon performance.

A major part of the conversation focuses on fueling marathon training while losing weight. They discuss periodizing calorie and carbohydrate intake around important sessions, why harder running dramatically increases carbohydrate requirements, fueling long runs, post-workout glycogen restoration and why an athlete's fitness remains more important than simply consuming more fuel.

Jordan also explains why blanket recommendations such as 60-90 g or 120 g of carbohydrate per hour may not be optimal for everyone. Individual carbohydrate oxidation rates, gut tolerance and training history can all influence how much carbohydrate an athlete can actually use. They finish with bone health, practical carbohydrate choices including white rice, bread, fruit and honey, and why developing good whole-food habits remains important for long-term health.

Timestamps

00:00 Meet Jordan Sullivan
00:05 Weight Loss During Training
00:40 Why Calories In Out Fails
04:28 RED-S Risk And Nuance
06:12 Diagnosing RED-S Limits
07:13 Intensity Versus Duration
08:04 Fight Camp Case Study
12:53 Performance Versus Health
14:17 Setting A Marathon Cut
16:20 Power To Weight Explained
20:24 Fueling And Periodization
24:46 Estimating Calorie Burn
27:06 Safe Weekly Loss Targets
33:32 Muscle Loss In A Deficit
38:15 Going Leaner 69 To 65
43:22 When To Cut In Marathon Block
44:11 Race Prep Weight Loss
45:25 Training Status Matters
53:11 Fueling Long Runs
54:31 Carbs Versus Fitness
01:02:56 Intensity Drives Carb Use
01:08:10 Personal Carb Oxidation
01:14:24 Bone Health Basics
01:16:39 Best Carb Food Choices
01:20:15 Whole Foods For Longevity
01:23:35 Wrap Up And Contacts

Matt recaps his 2:33 Sydney Marathon in jeans, then dives into recovery, weight loss, fueling, strength training, Melbourne Marathon goals and what comes next.

Matt Fox / Sweat Elite

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Three days after the Sydney Marathon, Matt breaks down his 2:33:38 run in jeans and what he is currently calling the fastest known marathon in jeans. He talks through the pacing strategy, running with the 2:35 pacer through 30km, dealing with hamstring cramping late in the race, how much the jeans may have slowed him down and how Sydney compares with a flatter marathon course.

Matt also goes deep into marathon recovery, including the roughly 310g of carbohydrates and 50g of protein he consumed in the first 90 minutes after finishing. He discusses sleep, returning to training after a marathon, strength and mobility work, cramping, chafing, shoe choices and why he believes his recovery has been significantly better than after many previous marathons.

Weight loss remains a major topic as Matt explains how he has gone from around 86kg to roughly 73kg over the past four months while continuing to train at a high level. He discusses calorie deficits on easier days, carbohydrate cycling around workouts and long runs, strength training while losing weight, GLP-1 use, maintaining power while getting lighter and why he believes reaching approximately 69kg could put him back around PB shape for Melbourne.

Matt finishes by answering listener questions on Sydney's hills, marathon course conversions, how long runners can continue improving with age, shoe durability, recovering between Sydney and Melbourne, preventing marathon cramps and future costume marathon attempts. He also shares his plan to move to Lisbon later this year and spend more time racing and training in Europe.

Episode Timestamps

00:00 Welcome back
01:02 Sydney Marathon Jeans Run
04:33 Pacing, Cramp and Gym
06:55 Recovery Carbs and Sleep
10:43 Guinness Record Confusion
14:18 Chafing and Gear Tips
15:15 Melbourne Goals and Weight Math
19:07 Comeback After Time Off
23:24 Strength Training While Cutting
26:49 Fat Loss Method and GLP-1
30:01 Calorie Tracking and Carb Loading
32:12 Carb Cycling and Weight Loss
33:45 Garmin Calorie Burn Debate
35:33 Healthy Leanness and Caveats
36:23 Weight Targets for Faster Marathons
37:48 Sydney Course Time Conversion
40:02 Crowds and PB Potential
40:44 Marathon PBs With Age
42:10 Running a Marathon in Jeans
43:18 Low-Calorie Days and GLP-1s
45:00 Shoe Rotation and Durability
46:02 Recovering for Melbourne Marathon
48:42 Costume Records and Charity
51:08 Collaborations, Cramps and Shoe Picks
54:09 Fueling Rules for Hard Days
56:21 Moving to Lisbon
58:51 More Diet Content and Wrap Up