Matt Fox - How & Why I Lost 8 Pounds in 2 Months While Marathon Training - Chicago Marathon Build-Up

Summary

Matt Fox reports a 101-mile training week with less than five weeks remaining before the Chicago Marathon. The video covers his recent weight loss, marathon build-up, and a half marathon he raced in Flossmoor.

Flossmoor Half Marathon

Fox finished fourth in 67:04, about 16 seconds off his personal best of 66:48. He ran alone for much of the race and felt fatigued after several high-mileage weeks.

• First 5K: He started too fast, passing 5K in 15:18. In hindsight, he thought a split closer to 15:40 would have been better.
• Around 10K: His GPS showed 30:57, though he estimated the actual split may have been closer to 31:10. He let training partners Colan and Blake go because their pace was too quick for him.
• Roughly 5K to 16K: With no one nearby to run with, his pace slipped from around 3:06–3:07 per kilometer toward marathon pace. He repeatedly considered stopping.
• Around 16K / mile 10: William passed him, and Fox did not have the energy to respond.
• Final 8K: He described the finish as a grind, with splits around 3:14–3:18 per kilometer. Despite struggling mentally and physically, he was glad he continued.

Colan finished in roughly 63:30–63:40, while Blake ran about 65:15. Fox thought a more even start might have put him around 66:20–66:40. He rated the course about 7/10, citing rolling hills, turns, and uneven road surfaces. He considered the weather good, though breezy.

Training and Weight Loss

Fox says he has lost about 8 pounds (3.5 kg) in two months, going from around 164 pounds (74 kg) to 156 pounds (70.8 kg). He hopes to reach roughly 69 kg by Chicago. He believes being lighter has helped his racing, partly because he ran well at a similar weight when he set his marathon personal best.

He emphasizes that he is describing his own experiment, not recommending weight loss during marathon training. He warns that under-fueling can harm training and health, including risks related to RED-S and disordered eating.

His approach has been to eat mostly filling, minimally processed foods on easy days and keep calories below roughly 3,000, while substantially increasing carbohydrates before hard workouts and long runs. He says he typically consumes around 200 grams of carbohydrates on easier days and loads up on foods such as rice and pasta before key sessions. He also describes using protein-rich snacks, flavored sparkling water, and short walks to manage cravings, and says Ketone-IQ shots have helped him control his appetite.

Key Workouts

• Tuesday: 5 × 1 km at threshold, around 3:05/km, followed by 10 × 500 m at roughly 10K effort, just under 3:00/km. Fox felt aerobically comfortable but had fatigue in his legs.
• Thursday: 10 × 100 m strides, replacing his usual hill sprints because the half marathon was coming up.
• The remaining sessions were mostly easy mileage. Fox expected another week close to 100 miles.

Training Q&A

Fox says he does not think easy-run pace needs to be fixed, and that the number of long runs over 20 miles is individual. He expects to do around six to eight such runs. He also says he prioritizes training, recovery, sleep, and nutrition over choosing particular shoes.

Presenters and Sources

• Presenter: Matt Fox
• Channel: Sweat Elite
• Named references: Ryan Hall, Tim Ferriss, and viewer questions from David and Sam
• Sponsors and promotional sources mentioned: HOVERAir X1, Ketone-IQ, and Kaizen